Aguablanca Dike along the Cauca River, Cali, Colombia

Transcription

Aguablanca Dike along the Cauca
River, Cali, Colombia
Diagnosis and recommendations
Final
NL Agency
The Netherlands Ministry of Foreign Affairs / Colombia Transition Facility
January 2013
Aguablanca Dike along the
Cauca River, Cali, Colombia
Diagnosis and recommendations
Final
file : BB2984
registration number : LW-AF20130064
version : final
classification :
NL Agency
The Netherlands Ministry of Foreign Affairs / Colombia Transition Facility
January 2013
© HaskoningDHV Nederland B.V. No part of these specifications/printed matter may be reproduced and/or published by print, photocopy, microfilm or by any other means, without the
prior written permission of HaskoningDHV Nederland B.V..; nor may they be used, without such permission, for any purposes other than that for which they were produced. The quality
management system of HaskoningDHV Nederland B.V.has been approved against ISO 9001.
Royal HaskoningDHV
CONTENTS
PAGE
EXECUTIVE SUMMARY
3
1
1.1
1.2
1.3
INTRODUCTION
Extreme rainfall in Colombia has led to alarm for possible dike failure
Scope of work
Project team
7
7
8
8
2
2.1
2.2
2.3
2.4
HYDROLOGY AND HYDRODYNAMIC MODELLING
Discharge of Rio Cauca under influence of Salvajina reservoir
Analysis of extremes leads to lower expected maxima than previously calculated
Identification of dike locations with critical elevation level
Flood modelling results
9
9
10
12
12
3
FLOOD RISK MANAGEMENT: COST OPTIMIZATION
13
4
4.1
4.1.1
4.1.2
4.1.3
4.1.4
4.1.5
4.2
4.2.1
4.2.2
IMPROVEMENT OF DIKE SAFETY, IMMEDIATE AND SHORT-TERM STRATEGY
Analysis of present conditions
Dike crest level of the main dike
Dike conditions of Canal Sur and Rio Cali
Water levels and river bed management
Freeboard discussion
Dike strength
Immediate and short term strategy
Immediate actions
Short-term strategy 0
15
15
15
17
17
17
17
18
18
19
5
5.1
5.1.1
5.1.2
5.1.3
5.2
5.2.1
5.2.2
5.3
5.3.1
5.3.2
5.3.3
5.3.4
LONG-TERM APPROACH FOR FLOOD PROTECTION CALI
22
Anticipate on impact of economic and regional developments and possible climate change effects22
Spatial developments
22
Economic development
22
Climate change
23
Ongoing and increased need for flood protection
23
Risk based approach for flood protection for Cali
23
Combination of flood risk and earthquake risk
23
Strategies for maintaining and improving flood protection
24
Flood protection level
24
Strategy 1: Controlled retention upstream of Cali and on east bank
25
Strategy 2: Total reliance on Jarillón Aguablanca
25
Choice of strategy
26
6
GOVERNANCE AND WATER AUTHORITY
27
7
REFERENCES
28
ABBREVIATIONS
30
COLOPHON
31
8
NL Agency/Aguablanca Dike along the Cauca River, Cali, Colombia
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31 January 2013, version final
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APPENDICES
1
2
3
4
5
6
7
8
9
10
Hydrology
Longitudinal dike profiles and hydrodynamic modelling results
Hydrodynamic modelling, methodology
Flood risk management methodology
Field assessment of the conditions of the Aguablanca dike
Structural stability and analysis of failure mechanisms
Inspection plan
Water governance and regional water authorities in the Netherlands (partially derived
from [14])
Ownership of the Aguablanca dike
Table of damage and investment costs
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EXECUTIVE SUMMARY
1
Commissioned by Agency NL , Royal HaskoningDHV in collaboration with Colombian consultant
Corporación OSSO, and supported with input by Dutch Waterboard Aa and Maas has made an analysis of
the status of the Aguablanca Dike along the Cauca River near Cali, and elaborated recommendations for a
short and long term strategy to improve its safety level.
Our main conclusions are the following:
1.
The Aguablanca Dike is basically a good dike, but enforcement and maintenance of the dike and river
profile over the past 50 years has been insufficient. This lack of maintenance leads to a number of
immediate and short term measures to be taken.
2.
The protected area has developed over 50 years from an agricultural area into a densely populated
urban area. This leads to the necessity for an increase in flood protection level as a long term
objective.
3.
Legally, at least until October 2012, CVC has been owner of the dike since its construction, but
responsibility for maintenance and control of the dike are not transparent.
Ad. 1
The present state of river flood protection of Cali has fallen below the standard of the original dike design
of the Aguablanca Dike in 1958 (T=100 + 1.5 m freeboard). With relatively limited effort this original flood
protection can be restored. The short-term strategy 0 (reference strategy) is aimed at this original
protection.
A serious point of attention is the lack of maintenance of the main pumping station in the dike body.
Immediate action is required to repair a number of the outer valves that are essential for flood prevention,
before a threatening situation may occur. EMCALI is owner of this pumping station.
Ad. 2
Since 1958, 700,000 to 800,000 people have come to live and work in the flood prone area of Cali.
Therefore the flood protection of these people and there economic activities needs to increase. In other
words, the Jarillón Aguablanca needs to be raised and strengthened.
Ad. 3
We have verified that, at least until recently, CVC has been the legal owner of the dike (see Annex 9).
During presentation of the results of this study on December 7, 2012, it came to our attention that CVC
may have signed away its ownership to the City of Cali during October or November 2012, but this has not
been verified through documents. Anyhow, more organisations are involved in decisions regarding
constructions on and near the dike. In this situation it is not transparent which organisation has ultimate
responsibility for the dike, leading to a questionable lack of maintenance and increase of inundation risk.
To have a solid defence against inundation from the Cauca River, it is a prerequisite to have only one
organisation ultimately responsible for control of the dike. Over the years, the involvement of CVC in
maintenance and control of the dike has diminished. Various structures in the dike body belong to other
1
Financed through the Transition Facility which is supported by the Ministry of Economic Affairs,
Agriculture and Innovation and the Ministry of Foreign Affairs
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entities like EMCALI and DAGMA. The different authorities lack communication on important issues of
design of new constructions and maintenance issues.
We have defined an action plan including technical and non-technical issuesactions to be taken and
strategies to follow.
Tabel 1
Urgent:
Action plan
1. Rehabilitation of pumping station
The condition of the closing systems of the pumping station Paso del Comercio is alarming. They are
either out of order or malfunctioning. Immediate action to repair broken or malfunctioning valves is
required to ensure maximum flood protection. This action cannot be postponed2.
2. Rehabilitate 6 critical points in the Aguablanca dike and low points in the dike of Canal Interceptor Sur
Where the dike crest level is the most important parameter in flood protection, immediate action is
recommended to rehabilitate the lowest points in the Aguablanca dike :
1
km 128+581
2
km 134+581
3
km 136+081
4
km 140+781
5
km 142+281
6
km 143+281
In addition it is recommended to rehabilitate the low points of the dike of Canal Interceptor Sur, which
have been identified in the longitudinal profile of Annex 2.
3. Remove ant nests and fill the cavities caused by these nests
The cavities of ant nests (hormiga arriera) need to be filled. Shallow nest cavities can easily be repaired
by digging out and applying new clay filling. Deeper nests should be filled, preferably with bentonite.
Short term:
1. Raise the security level of the dike
We recommend a security level for a return period of 500 years with a freeboard of 0.5 m. The extra costs
for a safety level with a return period of 500 years as compared to 100 years are relatively small.
2. Resettlement of house on the dike and in the berm of the dike
Approximately 15000 families are living on the dike and berm which need to be resettled.
3. Install by law one entity with ultimate responsibility for the dike
This entity should have responsibility for maintenance, inspection and supervision of all construction in
the dike, and have the technical and financial resources to perform its task properly.
4. Introduce a maintenance system
Develop a system for maintenance of the dike, including norms for interventions, constructions, housing,
2
In a letter to Dr. M. Guerrero, the Mayor of Cali, dated December 17, 2012, EMCALI has confirmed that it
is envisaged to repair the damaged valves in January 2013
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industries and a plan for periodic inspection.
5. Evaluate existing plans for dike re-enforcement
There are existing plans by EMCALI for dike re-enforcement around the drinking water plant. We
recommend an evaluation of these plans in cooperation with CVC and investigate alternatives in order to
reduce costs.
6. Control further spreading of the ant species “Arriera”
Regular inspection should be aimed at eradication of the ants. Ant nests should be dug out as soon as
observed.
7. Action for river bed and flood plain maintenance and construction debris control
Enforcement of river bed maintenance needs to be improved. This is on one hand predominantly a
government issue, on the other hand economical incentives and technical possibilities can help.
Especially the dumping of construction debris needs to be stopped.
8. Review the operation rules of the Salvajina reservoir
We recommend a review of the operation rules to attempt a further optimization of compliance with the
different objectives of the reservoir, i.e. reduce peak discharge, supply a certain minimum discharge for
environmental purposes and produce energy. This will require a simulation study based on historic
discharges, where we suggest to use stochastic modelling and use of generated synthetic time series. A
special point of focus is the time scale to be used, and possible use of meteorological forecasting.
Medium term and long term:
1. Improve land use planning
Water safety should be a leading principle in an integral approach of land use planning by the municipality
and regional authorities. It is therefore an important issue related to the institutional issues. Enforcement
of spatial management and assessment of spatial developments on consistency with the long-term flood
approach needs to be implemented. The analysis of this study should be incorporated into the land use
planning strategy of the municipality.
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In addition to the action plan, we have the following recommendations:
1.
Research into climate change effects
We recommend further research into the effects of the trend in the ONI (Oceanic Niño Index) on extremes
of the Cauca river discharge.
2.
Research into fluvial morphodynamics
We recommend that the fluvial morphodynamics of the river Cauca be studied in order to have a better
understanding of its morphodynamics and the influence of the human activities on the morphological
developments.
3.
Further research into river hydrodynamics
Develop an integrated hydrodynamic model of the river Cauca starting at Salvajina reservoir. In this model
the overtopping and flooding should be included. The model should be calibrated in order to reproduce the
last flooding events for instance by comparing the inundated area with aerial photographs.
We have understood that this model will be constructed in another project [5] and advise the local team to
participate in this study.
4.
More soil investigation for strength parameters related to dike slope stability
We recommend doing more triaxial tests on undisturbed clay samples of the dike body to gain a better
insight into the strength parameters along the profile of the Aguablanca dike. We suggest making and
executing a detailed plan, based on a number of indicative borings.
5.
River bed and flood plain maintenance and construction debris control
government issue, on the other hand economical incentives and technical possibilities can help. Especially
the dumping of construction debris needs to be stopped. A strong recommendation is to invest in debris
crusher systems to convert waste debris into raw construction materials, ready for re-use.
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1
INTRODUCTION
1.1
Extreme rainfall in Colombia has led to alarm for possible dike failure
Extreme rainfall in 2010 and 2011 has resulted in extreme river discharges and water levels in various river
basins in Colombia and has disrupted the lives of more than three million Colombians, uprooted thousands
from their homes and destroyed swathes of farmland.
In Cali, the threat of a possible breach of the existing dike system has alarmed the highest authorities. The
impact of such a breach on the city and the country has led President Santos to put urgent action to
improve the Aguablanca Dike protecting the city as top priority. The Aguablanca Dike along the Cauca
River in the municipality of Cali has a length of approximately 17 km. It is the only structural flood
protection of the city of Cali against floods from the Cauca River.
Juanchito
Figure 1
Schematic situation of Aguablanca Dike together with dike of Canal Interceptor
The dike was originally built in the late 50’s and early 60´s in order to habilitate the Aguablanca´s low lands
for agricultural purposes. However these areas have witnessed significant urban development. During the
last four decades the city has spread towards the river. Dwellings have been built on the dike crest, as well
as in the floodplain. Today almost 20% of the population of the city is settled in flood plain and around
15.000 people live directly over the dike structure. The largest water treatment plant that supplies around
60% of the city is also located in this area. The main pumping station of the city, Paso del Comercio, is
located in the lowest part of the city at the end of the principal drain channel.
A population of over 700.000 people in the District Aguablanca is currently at risk from flooding. Climate
change and progressive anthropogenic impacts in the upper basin of the Cauca River will only further
increase these risks.
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1.2
Scope of work
The scope of work has included the following activities:
1. Assessment of the physical condition and structural stability of the current dike. This includes:
● a field survey over a distance of 18 km;
● application of geotechnical software;
● review of previous surveys of the dike;
● training of the Colombian engineers of CVC during the process of dike inspection
2. Calculations using a hydrodynamic model to model inundations of different
frequencies (1:100 year 1:250 year, 1:500 year).
3. Estimation of the optimum dike height in terms of the costs of dike improvement and the flood
damage avoided.
4. Development of action plan and strategies for short term an medium term measures
5. Prioritization of sections of the dike that should be reinforced.
6. Organisation of a workshop with presentations of dike management in the Netherlands, preliminary
results of the inspection of the Aguablanca Dike, presentation of a dike inspection manual in Spanish.
1.3
Project team
The project team consisted of the following persons:
Hans Leenen (Royal HaskoningDHV): team leader and senior expert in hydrology and risk management
Michel Tonneijck (Royal HaskoningDHV): senior dike expert
Marcela Busnelli (Royal HaskoningDHV): senior expert in hydrodynamic and morphological modelling
Steven Sjenitzer (Royal HaskoningDHV): geotechnical expert
Joop de Bijl (Waterboard Aa and Maas): senior dike expert. For this project Joop de Bijl of Waterboard Aa
and Maas has participated to include expertise of a leading Dutch Waterboard.
Royal HaskoningDHV has collaborated with Colombian counterpart Corporación OSSO in Cali, whom we
greatly thank for its professional and kind cooperation.
Team members of OSSO were:
Carlos Regalado, geotechnical engineer and outstanding help in translation issues
Angela Cabal, specialist in hydraulic modelling
Jorge Mendoza, civil engineer
Henry Peralta, general coordinator
Andres Velasquez, socio-economist
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2
HYDROLOGY AND HYDRODYNAMIC MODELLING
2.1
Discharge of Rio Cauca under influence of Salvajina reservoir
The discharge of the Cauca River along the Aguablanca dike is influenced by the operation of the
Salvajina Dam, 139 km upstream of the hydrometric station of Juanchito (Figure 2). Juanchito is the most
important hydrometric station along the Aguablanca dike with water level data going back to 1934 and a
continuous time series since 1945. The Salvajina reservoir was put into operation in 1985 and is a multipurpose reservoir with the objectives of energy production and attenuating flood peaks on the Cauca
River.
Figure 2
Location of Salvajina Reservoir
The operation rules of Salvajina Reservoir are primarily on a monthly basis (but may be adjusted daily) and
are controlled by the Committee of Operation. Decisions are agreed upon by CVC and EPSA (Empresa de
energía del Pacífico S.A.). During the first days of each month the Committee defines the water release for
the month based on a set of operation rules, which will not be treated here in detail [1]. The monthly
strategy will be maintained as much as possible, but may be modified on a daily basis. One objective is to
maintain the discharge at Juanchito station between 130 m 3/s and 900 m3/s. The objective of the minimum
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flow is dilution of contamination. This flow can be regarded as an environmental flow. The envisaged
maximum flow provides a safe level against inundations by overtopping of the Aguablanca dike. As
observed in recent years, the applied operation of Salvajina has not been able to prevent much higher
flows at Juanchito station (see Annex 1) of up to an estimated discharge of 1148 m3/s in 2011.
The operation of Salvajina reservoir does not have strict optimization rules. We recommend a study to
optimize the operation regime, by applying simulation modelling of the reservoir using stochastic methods,
for instance with synthetic flow generation based on a Thomas-Fiering model. Such a modelling effort
should take into account the different conflicting objectives of the reservoir, i.e. generating energy on one
side, reducing flood peaks on the other, and also allowing for a certain environmental flow.
2.2
Analysis of extremes leads to lower expected maxima than previously calculated
In order to evaluate dike safety on the long term, it is common practice to apply a statistical approach on
existing data (Appendix 1) and determine return periods for different discharges, based on the best fit of a
certain probability function. This has also been done in previous studies, a.o. by the Universidad del Valle
[2]. To define return periods and discharges for the present conditions the data of water levels and related
discharges at Juanchito before 1985 cannot be used because of the influence of Salvajina reservoir. So
only the years since 1985 have been used in the analysis of return periods. The Universidad del Valle [2]
has applied a Gumbel distribution to the data, resulting in higher discharge data for return periods of 25
years and more, than what is calculated under the present study. The reason for the differences is that the
Gumbel distribution gives a rather poor fit to the data. Under the present study a number of probability
distributions have been compared for quality of fitting the data. The Log Pearson 3 provided the best fit,
based on statistical grounds (K-S statistic, see Table 2). A quick way to assess the applicability of various
probability functions is the so-called Moment-Ratio diagram, which shows differences between statistical
characteristics of the observed values and the theoretical distributions. (see Moment-Ratio diagram in
Annex 1). From this diagram it is clear that the Gumbel distribution is not suitable in this particular case.
Table 1 shows the differences that occur for return periods higher than 25 years. The difference between
the discharges for the return period of 100 years leads to a difference in water level of 0.67 m according to
the current calibration table for the level-discharge relationship (Annex 1). Our conclusion is that previous
studies have overestimated the discharges related return periods above 25 years.
As a basis for the hydrodynamic modelling the present study will apply the results from the Log Pearson 3
distribution as presented in Table 1, graphically presented in Figure 3.
Table 1
Comparison of estimated return periods (station Juanchito) with previous studies
Ref. [2]: Gumbel distribution
Present study: Log Pearson 3 distribution
Return period
Discharge [m3/s]
Discharge [m3/s]
5
839
925
10
961
1016
25
1115
1107
50
1229
1161
100
1342
1206
200
1244
250
1255
500
1286
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Return period estimates: Extreme discharges Juanchito-since 1985
[m3/s]
Observed
LP3
Gamma
Gumbel
Normal
Logistic
Weibull
LN2
LN3
2500
2000
1500
1000
500
0
1250
1
Figure 3
Table 2
10
100
Return period [time units]
1000
4000
10000
Return period estimates for extreme discharges at Juanchito
Kolmogorov–Smirnov test statistic
Probability function
KS-critic (0.10)
LP3
Weibull
LN3
Gumbel
KS-Statistic
0.232
0.093
0.099
0.105
0.128
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2.3
Identification of dike locations with critical elevation level
The discharge data as extrapolated with the LP3 distribution (Table 1) have been used to estimate the
water levels along the Aguablanca dike for various return periods. The Universidad de Valle [2] applied a
one dimensional model to estimate water levels for different return periods. In all modelling efforts, the right
bank of the Cauca River has been modelled as an infinitely high wall without inundation possibility. These
levels have been used as input for the estimation. In this estimation Juanchito station has been used as a
reference to adjust all levels along the Aguablanca dike accordingly. The water levels associated with
different return periods have been compared with the latest longitudinal dike profile, measured in 2012
(Annex 2). In doing so, the critical points along the dike in terms of level, were identified:
1
km 128+581
2
km 134+581
3
km 136+081
4
km 140+781
5
km 142+281
6
km 143+281
Based on these critical points inundation simulations were carried out with the 2D-model CCHE2D of the
University of Mississippi to establish a basis for damage estimates (see Annex 2).
2.4
Flood modelling results
The 2D-model CCHE2D of the University of Mississippi of the river Cauca (between the Canal Interceptor
Sur and the river Cali) has been applied in this study [3]. The model was recalibrated based on the
updated statistics of discharges and water levels. The hydrodynamic model provides insight in flood
characteristics, such as water depth and flow velocity. Three scenarios were defined and simulated as
input for the risk management assessment (Chapter 3): Flooding due to breaking by overtopping for a
return period of 1:100, 1:250 and 1:500. The graphical results of the computations for a return period of
1:100 are presented in Annex 2. Numerical results of the computations are presented in Table 3. These
flooding characteristics have been applied in the risk-based analysis to obtain the damage costs
corresponding to a certain flooding probability.
Table 3
Characteristics flooding scenarios
Return period Maximum inundated area [km2]
100
20.36
250
22.83
500
24.28
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3
FLOOD RISK MANAGEMENT: COST OPTIMIZATION
Initial costs of relocation of dike dwellings play an important role in total costs
In this study we apply the principles used in the Netherlands for risk-based design of flood protection
systems to the Aguablanca area. In this economic optimization, the investments in more safety are
balanced with the reduction of the risk to find an optimal level of flood protection.
We have assumed that the dike will only fail because of overtopping. The strength of the dike is
subsequently designed in such a way that the dike does not fail at water levels below the design water
level, for all possible failure mechanisms such as piping and lack of stability. The assessment of the
physical conditions and structural stability of the dike is described in detail in Annex 5, and Chapters 4 and
5. If the water level is above the design water level, the dike might fail and breach.
The places where overtopping might occur in the river Cauca (between Canal del Sur and river Cali) for a
given return period were obtained by plotting the crest height and the water levels corresponding to a
given return period. The flooding scenario for a return period of 100 year was defined by comparing the
height of the dike with the water level for a return period of 100 year.
The locations where defined from a preliminary longitudinal profile of the dike. The OSSO-team corrected
this profile after reviewing it. The locations of possible breaching of the dike were determined by the
OSSO-team. The longitudinal profile of the dike at the left bank of the river Cauca shows sectors where the
height of the dike is close to or lower than the water level for a return period of 100 years. Five locations
were defined. In these locations the water level is higher than the dike or the free-board is less than 1 m. A
free-board of 1 m is recommended by CVC.
Table 4 shows the locations where overtopping might occur. The dimensions of breaching of the dike were
obtained from the analyses of failures of dikes occurred in the past in Colombia [13].
Table 4
Locations where overtopping might occur
Abscisa
Crest of
the dike
[m]
Tr 100
Tr 250
Tr 500
1
K134+581
952.5
952.06
952.30
952.45
2
K136+081
951.6
951.61
951.85
952.00
3
K140+781
950.6
950.76
951.00
951.15
4
K142+281
950.5
950.20
950.44
950.59
5
K143+281
950
949.82
950.06
950.21
Location
No.
Water level [m]
The 2D hydrodynamic model has been applied to determine the flooding characteristics. These flow
characteristics and the land use maps were combined in GIS with the stage-damage functions and
maximum damage costs to determine the damage costs corresponding to a flooding probability.
The current yearly risk (probability x damage) has been converted to a present value by dividing by the net
discount rate. A real discount rate of 8% is calculated from the interest rate of 11% minus inflation 3%.
The damage will increase because of economic growth. Neglecting economic growth would lead to an
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underestimation of the future risk. We have assumed a economic growth of 1% per year. This number is
estimated on the basis of future expectations and is therefore uncertain.
In a cost-benefit analysis also the costs of rising and reinforcing the dikes are important. The costs of
relocating the families living on the dike are also taken into account in the investments. The results of the
analysis are presented in Figure 4. An important feature of this calculation is that the increase in
investments costs as a function of the return period is relatively small. This is because the costs of
relocation the families living on the dike are the highest investment costs. This aspect leads to the
consideration, that from the purely economic point of view of this method, it would be better to make a
choice for the highest return period, leading to the lowest total expected costs. From a practical point of
view, any choice above 500 years would seem sufficient. The background data of this calculation are
presented in Annex 10.
Figure 4
Results of economic optimization for the Aguablanca dike
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4
IMPROVEMENT OF DIKE SAFETY, IMMEDIATE AND SHORT-TERM STRATEGY
4.1
Analysis of present conditions
The objective of the assessment of the present conditions of the dike is to investigate crest levels, stability,
and all human or other impacts, that may reduce the safe level of the dike. Comparing these conditions
with required conditions leads to conclusions about possible strategies and necessary actions to take.
Dike crest level of the main dike
The original design crest level for the Jarillon de Aguablanca was based on T=100 + 1.50 m. This dike
protected a predominantly agricultural area between Cali and the Cauca River. The dike was constructed
in an era (1950s) that T=100 could not be well calculated, but only be estimated [15]. The present crest
level is presented in Figure 5 The estimation of the 1950's shows very good compliance with the now
calculated T=100 in this report3.
From the analysis we have the following observations:
1.
Crest level measurements show that the crest level could not be maintained all along the dike.
2.
The protected area has changed from agriculture into urban area and therefore requires a higher
protection level (see paragraph 4.1.3).
3.
The original 1.50 m freeboard could well be reduced since the expected water levels can be
calculated more accurately.
Perfil Longitudinal del Jarillón del río Cauca y Nivel de agua para diferentes periodos de retorno
(Versión revisada con datos de campo, septiembre 20 de 2012)
Level [msnm]
956
955
954
water level T=10
water level T=25
water level T=100
water level T=250
water level T=500
dike crest level
T=100 + 0,50 m freeboard
original design T=10 + 2,50
953
952
951
950
949
948
Juanchito
km 139 + 259 m
Canal Sur
km 127 + 724 m
Rio Cali
km 146 + 300 m
147
146
145
144
143
142
141
140
139
138
137
136
135
134
133
132
131
130
129
128
947
127
4.1.1
---> x -coordinate [km]
Figure 5
Dike crest level (orange) and different water levels + freeboard (see also Annex 2)
3
With the few data the engineers had in 1958, they estimated the level corresponding to a return period of
T=100 years + 1.5 m, to coincide approximately with a level corresponding to a return period of T=10 years
+ 2.5 m
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Table 5 Dike lengths to be raised for distinguished flood protection levels
possible
dike length
freeboard
cm to be
protection
to be raised
remarks
[m]
raised
levels
[m]
with the knowledge of today's water level
calculations the dike doesn't meet the
originally set requirements;
almost
T = 10 yrs
1.50
an extra check on the datum is required,
total
since there is no straightforward explanation
for why the Jarillón Aguablanca has fallen so
far below its original standard
with today's more accurate water level
generally
calculations, flood protection level of T=100
T = 100 yrs
0.50
4300
< 20 cm
could be guaranteed with a freeboard of
0.50 m
with the change of the protected area from
generally
agriculture into urban area, a higher
T = 250 yrs
0.50
7200
< 35 cm
protection level needs to be considered and
should be a result of an economic analysis
generally
idem
T = 500 yrs
0.50
9800
< 40 cm
From this it is clear that the discussion about the safety level is
1.
on one hand a matter of the establishment of an economical optimum return period, but
2.
on the other hand a technical freeboard discussion among engineers about the reliability of the water
level calculations.
Accurate dike levels and accurate water levels.
In the course of the assignment it turned out to be very difficult to establish the correct dike level from the available data.
Level data were either outdated or, more important, taken from different periods in which the reference level (datum)
had changed. CVC and OSSO have assured that the presently available dike level is correct.
The hydraulic river model for water level calculations is by definition not exact, since not all riverbed data are available,
nor can calibration and verification be done. Still the possibilities for establishing a more or less correct water level are
way better than at the time of dike construction. A river model for the whole Cauca River should be made available. First
of all, river behaviour downstream is very much affected by what happens more upstream. The acceptance of one base
for transboundary decisions (between states, between municipalities depend very much on the acceptance of one base
model as the true water level predictor.
Still the reproduction of the original dike design (Figure 5) shows that the dike has dropped considerably below its
original design value (water level T=10 + 2.50 m). This is not in line with the feeling and view of experienced local
engineers. We recommend that this item will be investigated:
1.
re-evaluate datum changes in the course of years
2.
attribute each available measurement to the correct datum
3.
describe the history of datum levels and measurements in a separate report
4.
open archives to establish certainty about the really constructed dike level: T=10 + 2.50 m indeed?
5.
compare the starting point T=10 (1958) and T=10 (2012)
6.
investigate the possibility that the dike subsoil has consolidated so much.
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4.1.2
Dike conditions of Canal Sur and Rio Cali
There are no records of failure of the dike along Canal Sur. Stability calculations for these dikes have also
indicated that they comply with the minimum strength requirements [13]. Corporación OSSO has done field
work for the dikes of the two tributaries Canal Sur and Rio Cali resulting in the longitudinal profiles
presented in Annex 2.
The field observations show a significant impact of human interventions along these dikes in the form of
waste and rubble deposits. In addition there are nests of the ant species “arriera” in various locations,
impacting the permeability and stability [13].
From the profiles it follows that there are some parts below the T=100 level that is defined at the point of
inflow into Rio Cauca. The right embankment along Rio Cali seems everywhere, except a small part close
to the Rio Cauca, well above the T=100 level as defined at the point of inflow into the Rio Cauca.
4.1.3
Water levels and river bed management
Because of the intense urbanization, the river bed and flood plains condition is very much under pressure
of sand mining and dumping of construction debris. Uncontrolled erosion and upward trends in water levels
are a result. Of course CVC and Cali municipality are fully aware of this problem. The solution of the
problem is not just a technical item, but is found in a much wider socio-economic and administrative
approach.
4.1.4
Freeboard discussion
In the Netherlands river dikes require a minimum freeboard of 50 cm. This freeboard allows for
●
wave run-up,
●
river water level model uncertainty and
●
firm dry ground above the water level in extreme conditions for emergency measures.
In the situation of the Cauca River and the Jarillón Aguablanca, wave run-up may be neglected. The width
of the river is relatively small and there are no big cargo ships. The model uncertainty however needs to be
regarded more in detail. For the moment we assume that model uncertainties fit well within the 0.50 m
allowance for the freeboard.
4.1.5
Dike strength
The crest level is the most important and direct factor for the flood level protection of Cali. However, a
weak dike or weak points in the dike may result in failure, even if the water level is lower than the design
water level.
The dike inspection has resulted in 5 important observations.
1.
Dike crossing hydraulic constructions Water and Sewer Treatment Plants and Pumping Station do
not fulfil safety requirements. Especially the pumping station at the downstream side of the dike is in
an alarmingly bad condition. Failure of the pumping station in its flood defence function cannot be
excluded and is estimated much worse than a failure probability of 1/100 per year (T=100). Also the
drinking water inlet and waste water treatment plant need upgrading. For a more elaborate
description see Annex 5, Field assessment of the conditions of the Aguablanca dike.
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2.
3.
4.
5.
At high water levels some water seepage near the pumping station of Paso del Comercio has been
observed, most likely due to a construction error and not to slope instability. Signs of piping effects
have not been observed.
Ants have infested the dike and its environment (hormigas arrieras). They make their dwellings in the
dike, causing cavities and weakening the dike.
Under the top clayey and silty layers there are some locations with a layer of liquefiable sands.
Earthquake induced liquefaction may put the dike as a water retaining function out of order for long
time. However, the risk of a coincidence of a major earthquake and a flood is negligible compare to
the risk of the event of either a major earthquake or a major flood. Minor earthquakes in the past
have not lead to liquefaction. Therefore liquefaction is not considered an issue.
The dike is quite densely inhabited, predominantly at the northern stretch. Housing, foundation and
cellars and trees cut into essential minimum design profile. Living on a dike is almost the safest place
in a flood prone area. The major problem is when housing or other human activities harm the integrity
of the dike body: cut into the body itself, damage the revetment, thus reducing the water retaining
capacity and creating initiation points for erosion.
4.2
Immediate and short term strategy
4.2.1
Immediate actions
Low spots
Where the dike crest level of the main dike is the most important parameter in flood protection, immediate
action is recommended to raise the lowest points in the Aguablanca dike that are very local:
1
km 128+581
2
km 134+581
3
km 136+081
4
km 140+781
5
km 142+281
6
km 143+281
In addition it is recommended to rehabilitate the low points of the dike of Canal Interceptor Sur, which have
been identified in the longitudinal profile of Annex 2.
Pumping station maintenance
The condition of the pumping station is alarming. A number of the outer valves of the pumping station are
not functioning. Although the pipes have inner valves, the defence against flooding should not just rely on
these inner valves. During a flood, there will be unnecessary pressure inside the pipes, and increase the
risk of inundation. Immediate action is required to ensure flood protection4.
4
In a letter to Dr. M. Guerrero, the Mayor of Cali, dated December 17, 2012, EMCALI has confirmed that
it is envisaged to repair the damaged valves in January 2013.
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4.2.2
Short-term strategy 0
This short term strategy consists of 5 components:
a. Maintaining dike level at T=100
b. River bed and floodplain maintenance
c. Hydraulic constructions
d. Dike slope stability
e. Harmful activities from humans and ants
f. Institutional issues
These will be elaborated below (Institutional issues are discussed separately in Chapter 6).
The short term strategy should be considered as a base strategy (maintaining the status quo is not an
option). This mix of components should be implemented in a coherent way. Only maintaining the dike level
at T=100 will improve safety conditions but will not be effective in the long run if components b, c,d, and e
are not taken care of at the same time.
a. Maintaining dike levels at T=100
For the short term strategy 0, the measures are aimed at realising the originally intended protection level of
T=100. The measures respond to the findings of the dike inspection for the Aguablanca dike on 18/19
September 2012 and 2 October 2012. As regards the dikes along Canal Sur and Rio Cali, we recommend
the same immediate action, i.e. to bring the levels up to the corresponding T=100 level of the Rio Cauca.
Considering that the intended flood protection level of the Jarillón Aguablanca was T=100 + freeboard we
recommend for the short term to rehabilitate the dike to this flood protection level. Since the protected area
has changed from agricultural land into urban area, this protection level should at least be maintained. This
recommendation implies raising 4300 m of the dike. In doing so, we assume that with the present statistics
and calculation methods a freeboard of 0.50 m is sufficient.
NB. If it would be decided to raise the dike, the reinforcement could well be combined with the longer term
recommendation at little extra costs.
The T= 100 does not necessarily need to be motivated with an economical analysis. Rather, the situation
of Cali is such that the opposite river bank is lower and in much worse condition than the Cali side. This is
for Cali a preferential situation. There is so much retention on the opposite river side that Cali is virtually
safe. In this situation Cali or CVC could buy time: as long as developments upstream and/or the opposite
river bank do not go so far that Q or h near Cali will rise, the Jarillón Aguablanca will provide virtually
unlimited flood protection (as long it is strong enough, mind e.g. the pumping station).
b. River bed and flood plain maintenance and construction debris control
government issue, on the other hand economical incentives and technical possibilities can help. Especially
the dumping of construction debris needs to be stopped. A strong recommendation is to invest in debris
crusher systems to convert waste debris into raw construction materials, ready for re-use.
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Figure 6
Debris crusher system
c. Hydraulic constructions
From the safety assessment of the Pumping Station immediate action is required.
In general we recommend a situation in which the owner of the construction (EMCALI) and the owner of
the dike (CVC) are equally responsible for the construction part that crosses the flood defence line. This is
predominantly a governance issue to enforce this kind of collaboration, but it is also an issue of behaviour
of the engineers of both organisations (see also Chapter 6).
Technically we recommend EMCALI and CVC to co-operate on the ongoing projects for improvement.
From a flood defence perspective a number of design issues in the rehabilitation of the structures need to
be standardised:
1.
construction level should be in conformity with – future – dike protection level; preferably far beyond
the planning period (dike 50 yrs ahead, constructions – more expensive to adapt – 100 years ahead);
2.
overall stability of the construction must fulfil stability requirement as of the dike (water levels, piping);
3.
seepage screens next to and under the construction are required;
4.
integrity of the construction within the flood defence line must be guaranteed, preferably the parts of
the construction in the flood defence line must be stronger than parts outside the defence line; e.g. a
steel pipe crossing the dike must partly be stronger in the dike: if a pipe under pressure would fail,
that would be rather outside the dike than inside;
5.
transition constructions from e.g. concrete to soil need to be well designed, monitored and
maintained.
EMCALI has projects running. From the dike perspective the hydraulic constructions need upgrading in the
short term strategy. Where total rehabilitation does not fit into the life cycle economics of the structure,
measures should be taken to ensure the flood protection part of the structure. Assessment and design
aspects have been mentioned above.
d. Dike slope stability and liquefaction
The Jarillón Aguablanca has geotechnically relatively steep slopes. During the – still relative low –
2011 flood dike instabilities have been observed. In order to technically guarantee dike stability under
design conditions the slopes should be more stable. I.e. the dike needs gentler slopes. Example
geotechnical calculations show that a slope of 1:2½ to 1:3 will be required.
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Secondly the presence of liquefiable sands adds earthquake risk to the dike construction. Soil investigation
made available shows that the omnipresent sand layer is not always liquefiable.
We recommend to do density tests and test on grain size distribution and water content to localise the
potential liquefaction areas.
Given the Cali situation two options need to be investigated:
●
"adding cohesion" to the liquefiable soil
●
adjustment of the dike profile, so that deformation caused by liquefaction will not affect the water
retaining integrity of the dike (PLAXIS-calculations).
e. Harmful impacts from humans and ants
Houses and trees cutting into essential parts of the dike profile should be either removed or the dike profile
needs adaptation. We recommend the establishment and registration of minimum essential water retaining
dike profile for each section. This dike profile should have a legal status by which CVC is capable of
enforcing measures to maintain the minimum profile.
The cavities of ant nests (hormiga arriera) need to be filled. Regular inspection should be aimed at
eradication of the ants. Ant nests should be dug out as soon as observed. Shallow nest cavities can easily
be repaired by digging out and applying new clay filling. Deeper nests should be filled with preferably
bentonite.
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5
LONG-TERM APPROACH FOR FLOOD PROTECTION CALI
The long term approach for flood protection depends strongly on future developments of natural causes
and human activities. In this chapter developments are mentioned briefly. Essential for the developments
is that they are beyond control of the dike authority as well as local and regional authorities. Yet they are
an important factor that has implications for the way the flood protection in the future should be managed.
5.1
Anticipate on impact of economic and regional developments and possible
climate change effects
We consider scenarios as developments beyond control of the dike authority and other authorities for the
region. Climate changes, effects of El Niño and La Niña, urban development population growth, economic
developments are not within the immediate control of the dike authority and set boundary conditions for the
dike.
5.1.1
Spatial developments
Spatial development is an item that is not directly within the competence of a dike authority. This is rather
the domain of the municipalities, “departamentos” and provinces. With respect to flood protection spatial
development is an essential asset.
1.
Room for – natural – river inundations needs to be maintained to control river water levels. Not only
in the area Aguablanca, but more important upstream of Cali.
2.
Where Cali is an important area to be protected, the opposite bank still has a lot of land of lower
economic investment; the flood protection of Cali can well benefit from maintaining this situation:
keep the protection level at the opposite bank lower than on the Cali side. In terms of spatial
planning: make sure that the east side of the river can remain an emergency overflow basin.
3.
Upstream developments and climate effects will in the future cause higher river water levels near
Cali, requiring higher and wider dikes. The dike authority CVC should be given authority to claim and
free the land adjacent to the dike.
Water safety should be a leading principle in an integral approach of land use planning by the municipality
and regional authorities. It is therefore an important issue related to the institutional issues
5.1.2
Economic development
Figure 7
Urbanization development
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Economic and spatial developments go hand in hand. Figure 7 shows the development of 50 years. More
than climatic change, land use is a driver for an increased flood protection level. In Chapter 3 we have
presented a method for economical analysis to define an optimum flood protection level. Dike construction
and dike reinforcement require major investments and have major impact on the environment. It should
also be considered that creation of a flood protected environment will attract more investments within the
protected area, thus causing a greater need for good flood protection.
5.1.3
Climate change
Data that were analyzed in the recent study of the inundations in la Mojana [16], have shown a positive
correlation between the occurrence of La Niña and extreme discharges in the Rio Cauca, while it has also
been shown that the there is a trend in the ONI (Oceanic Niño Index), indicating an upward trend in the
occurrence of La Niña. The conclusion was that the statistical characteristics of the Cauca River are
changing. We conclude that besides the change of land use the occurrence of floods in the Cauca Valley
is also influenced by climatic effects, the extent and magnitude of which is yet unknown. We recommend
further research into the effects of the trend in the ONI on extremes of the Cauca river discharge.
5.2
Ongoing and increased need for flood protection
5.2.1
Risk based approach for flood protection for Cali
A flood is a major disaster in term of risk for loss of life, flood damage and setbacks in a long-term
economic development.
The Netherlands have adopted a risk based approach for flood protection. The basic philosophy is that the
authorities of the flood prone area have a responsibility in "insurance of economic development, life and
flood protection". For a society as a whole it is then economically attractive and feasible to invest in a
sound flood protection. In the case of Cali it is therefore economically attractive to invest in river works and
dikes.
For the long term we therefore recommend the risk based approach. This comprises several actions:
1.
acquisition of knowledge on risk based approach in flood protection
2.
implementation in guidelines for dike design
3.
implementation in practical operation CVC
4.
thorough implementation of a risk based assessment for the Cali situation (project)
5.2.2
Combination of flood risk and earthquake risk
In an area exposed to major natural disasters the combined disaster risk is important. Cali is a disaster
prone area regarding floods and earthquakes. The Colombia government has established a Construction
Code requirement regarding earthquakes. A design earthquake of 7.8 on the Richter scale, resulting in
0.25 g ground accelerations is an important design factor for constructions. For Cali this design earthquake
has a design return period of T = 475 years. We have the following observations:
1.
living in Cali, exposure to an earthquake cannot be avoided;
2.
flood risk adds to the exposure for people to disasters;
3.
expected flood damage will add to the expected damage from disasters,
4.
earthquake damage remains dominant
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A severe earthquake may result in considerable damage to the dike, which – besides all other damage to
the city - would require immediate attention. Since the time of construction of the dike, no damage has
been observed due to earthquake. To evaluate the risk of liquefaction due to an earthquake, we
recommend more research into liquefaction prone areas.
Looking at the risk of exposure to a disaster, the combination of a T=100 years flood protection with a
T=475 years earth quake risk, would result in probability of disaster, which is high relative to a person’s life
expectancy. A person, living 80 years in a flood and earthquake prone area runs the risk of 68% to be hit
by at least one of the two. Where the earthquake can hardly be avoided once living there, reduction of this
exposure is well possible by increasing the flood level protection. For instance, the combination of a T=500
year flood risk with a T=475 year earth quake risk, would result in a probability of 28% of being hit by at
least one of the two disasters in a period of 80 years.
From the damage point of view the earthquake risk is quite high. Considering that a dike breach would not
result in very high inundation depths in Cali, damage is severe, but would still be limited in comparison with
a major earthquake. Economic optimisation will therefore decide on the optimum flood protection level.
In Chapter 3 we have shown that, having done the initial investment for dike improvement (predominantly
resettlement), a high flood protection level is economically attractive. The small differences in cm between
the low frequency water levels (T=100 to T =2000 and higher) demand little extra cost for great value in
avoided damage.
5.3
Strategies for maintaining and improving flood protection
From the above considerations two main strategies for the Jarillón Aguablanca can be formulated.
1.
The first strategy aims at "keeping the pressure on the dike low". Mitigation of rising river water levels
is the guideline for this strategy. This involves sound spatial planning.
2.
5.3.1
The second strategy assumes that spatial development can hardly be controlled when it comes to
flood protection. Retention capacity more upstream and opposite to Cali will gradually disappear for
other developments, forcing Cali to rely more and more on the flood protection of the Jarillón
Aguablanca.
Flood protection level
Based on the scenarios, the right margin of the Cauca River will probably become economically more
valuable than at present. It is therefore expected that the right margin will also be better protected against
floods. Socio-economic developments more upstream will lead to the construction of more upstream flood
protection works. As a result the flood protection level of Cali that is provided by the dike at its present
level will decrease. After all, reduction of room for inundation of river water will decrease the upstream
retention capacity and therefore have an upward trend in river water levels at Cali. This goes along with an
increased need for flood protection: economic development and growth of population and properties in Cali
will demand safety.
From the economic analysis it is clear that an economic optimum can be found in raising the protection
level of the Jarillón Aguablanca to at least T=500. Higher protection levels can be acquired at little extra
costs.
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5.3.2
Strategy 1: Controlled retention upstream of Cali and on east bank
Based on the present behaviour of the river water levels there is still sufficient room for retention of river
water upstream of Cali and on the right bank. A good 2D river model would need to be developed to
confirm this. In the calculation of river water levels at lower frequencies (T=250, 500, 2000 etc) the right
margin has been modelled as a infinitely high dike and a statistically extrapolated inflow from upstream.
Reality will be that Jarillón Aguablanca is the strongest point and that at lower frequencies, higher
discharges water levels will show little rise because of inundations elsewhere.
Water authorities in the States Valle de Cauca and Cauca might be able to maintain the upstream river
retention capacity, although experience shows that spatial development is rather difficult to control.
This strategy therefore comprises:
1.
upgrading of the Jarillón Aguablanca according to strategy 0
2.
further upgrading of the Jarillón Aguablanca to a higher protection level T=500 up to T=2000; this
further upgrading needs to be done along with strategy 0 to avoid double initiation costs; it needs to
be based on a good new 2D river model; relocation of all housing may even be avoided;
3.
CVC and their upstream colleagues will need to co-operate intensively, the same holds for the State
authorities
4.
Enforcement of spatial management and assessment of spatial developments on consistency with
the long-term flood approach needs to be implemented. Special areas – now being part of the river
retention area already – need to be dedicated for controlled flooding at large scale.
Figure 8
5.3.3
The three strategies shown in the flood-frequency graph
Strategy 2: Total reliance on Jarillón Aguablanca
The assumption for strategy 2 is that spatial management and maintaining retention areas available for
flood protection fails. As a result Cali will face higher extreme water levels. Cali will need to raise the
Jarillón Aguablanca to maintain – and raise – its flood protection level. Also in this strategy Cali's flood
protection level depends on upstream developments and on its own way of operating the right margin of
the Rio Cauca at Cali.
This strategy comprises:
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1.
2.
3.
4.
5.3.4
upgrading of the Jarillón Aguablanca according to strategy 0
further upgrading of the Jarillón Aguablanca to a higher protection level of T=500 up to T=2000
resettlement of all houses on the dike and in the berm of the dike cannot be avoided;
considerable enlargement (widening) of the dike needs to be accounted for
Choice of strategy
The presented strategies were developed with an open mind not wanting to limit ourselves a priori, and
without looking at financial or institutional implications. Taking a closer and more realistic look at the
possibilities, we recommend the choice for strategy 2. This strategy is included in the action plan. We
recommend a safety level with a return period of T=500 years. The arguments are the following:
1.
2.
Spatial development is a process which is very difficult to control and includes too many parties.
The strategy which includes use of designated retention areas may therefore prove impossible to
realize or be unreliable in the future.
The extra costs involved in going from a protection level with T=100 year to T=500 years are
marginal as compared to the overall costs
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6
GOVERNANCE AND WATER AUTHORITY
The organisational framework for river and dike management for the Cauca River, its tributaries and the
dikes, is scattered. In 1993 river and dike management were divided along political and administrative
boundaries. The Corporación Autónoma Regional del Valle del Cauca (CVC) was split in terms of both
geographical authority and content wise. Cauca was separated from Valle del Cauca and environmental
was separated from technical contents. This had very adverse effects on dike maintenance and
management, resulting in deterioration of the dike. Part of this deterioration has been caused by illegal
housing and other illegal activities on and around the dike.
Officially CVC is owner of the dike body5 and should still have responsibilities for maintenance and
management. In practice this is not the case and at the same time CVC does not have sufficient technical
staff to fulfil such a task. However, within the Colombian setting of authorities, CVC comes closest to being
a regional authority involved in water management, although its tasks related to management of the dike
are not clearly described. Authorities like EMCALI are responsible for certain constructions in the dike
body, such as the main pumping station, and the drinking water intake. However, there is hardly any
consultation with CVC about their activities for renovation and status of the construction works, whereas
these constructions are part of the defence of the dike.
It follows that there is no protocol for dike management and maintenance because obviously there is no
organization that holds complete responsibility. We recommend that maintenance and control of the
Aguablanca dike comes under one authority only that has the legal mandate to do so, respected by all
other organisations. This authority should have the legal right to inspect, monitor, evaluate plans and grant
permissions of any construction that is part of the dike and thus part of the defence against inundations.
There is more to this issue than management of the dike near Cali alone. It is about management of the
whole Cauca River from the Salvajina Dam up to and beyond Cali that should be managed by one
authority, and regulated by law. We recommend a dialogue between the parties concerned, led by the
mayor of Cali, or by the central government, to resolve this issue.
As an example of a water authority framework Annex 8 presents an introduction of the Dutch organization
of regional water authorities.
5
At the time of writing the draft report in November, this still appeared to be the case, i.e. until November
7, 2012; on December 6, 2012, we were informed that CVC has signed of its ownership to the municipality,
but we have not seen the documents to confirm this.
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7
REFERENCES
[1] Caracterización y modelación matemática del Río Cauca - PMC FASE III; Evaluación y optimización
de la regla de operación del embalse de Salvajina, VOLUMEN XVI, Universidad del Valle, Facultad de
Ingeniería, Escuela de Ingeniería de Recursos Naturales y del Ambiente, Santiago de Cali, mayo de
2007.
[2] Modelación matemática del sistema Rio Cauca-Humedales; Universidad del Valle, Facultad de
Ingeniería, Escuela de Ingeniería de Recursos Naturales y del Ambiente, Grupo Hidráulica Fluvial y
Marítima – HIDROMAR, Santiago de Cali, Agosto de 2009; Convenio Interadministrativo 144 de 2008
entre la CVC y la Universidad del Valle.
[3] Lit 1. Modelación de amenaza por inundaciones en la ciudad de Cali por el Río Cauca y tributarios,
incluye mapa de amenazas, batimetría y topografía en ambos costados. Informe final. Versión 01.
Hidro-Occidente S.A.
[4] Lit. 2. Modelación matemática del sistema Río Cauca – Humedades. Volumen 1. Universidad del
Valle. Facultad de Ingeniería. Escuela de Ingeniería de Recursos Naturales y del Ambiente. Octubre
2009.
[5] Lit. 3. Proyecto Corredor del Río Cauca (CVC).
[6] Lit. 4. Best Practise Guidelines for Flood Risk Management. The Flood Management and Mitigation
Programme, Component 2: Structural Measures & Flood Proofing in the Lower Mekon Basin.
Deltares, Royal Haskoning and UNESCO-IHE. Draft final report. May 2010.
[7] Lit. 5. Penning-Rowsell, Chatterton, J.B. (1977). The benefits of flood alleviation – a manual of
assessment techniques, Saxon House, ISBN 0566001908.
[8] Lit. 6. Dutta, D., Herath S., Musiake K. (2003). A mathematical flood loss estimation, Journal of
Hydrology, 277:24-49.
[9] Lit. 7. Kok M., Huizinga H.J., Vrouwenvelder A.C.W.M., Van den Braak W.E.W. (2005).
Standaardmethode2005 schade en slachtoffers als gevolg van overstromingen, HKV report
PR.999.10.
[10] Lit 8. Jonkman S.N., Bockarjova M., Kok M., Bernardini P. (2008) Integrated Hydrodynamic and
Economic Modelling of Flood Damage in the Netherlands, Ecological Economics 66, pp. 77-90.
[11] Lit. 9. Metodología de Modelación Probabilista de Riesgos Naturales. Informe Técnico ERN-CAPRAT1-5. Vulnerabilidad de edificaciones e infraestructura. ERN. Consorcio Evaluación de Riesgos
Naturales – América Latina. Consultores en Riesgos y Desastres. Tomo I.
[12] Rijkswaterstaat 2005. Standaardmethode2004. Schade en Slachtoffers als gevolg van
overstromingen. Kok M., Huizinga H.J., Vrouwenvelder A.C.W.M., Barendregt A. DWW-2005-005
[13] Informe de avance n° 2. Contrato de consultoría n° 101 de 2012 celebrado entre el fondo adaptación
y corporación observatorio sismológico del sur occidente contrato de consultoría n° 101 de 2012
LW-AF20130064
- 28 -
Royal HaskoningDHV
celebrado entre el Fondo Adaptación y Corporación Observatorio Sismológico del Sur Occidente;
Corporación OSSO, Cali, octubre 29 de 2012
[14] Water governance, The Dutch regional water authority model; Unie van Waterschappen, 2011
[15] Aguablanca Project 18 November 1958, Hadjikoulas, Kirpich, Corporación Autonoma Regional del
Cauca
[16] Flood risk management for La Mojana; Deltares, Royal HaskoningDHV, HKV; august 2012; Agency
NL
LW-AF20130064
- 29 -
Royal HaskoningDHV
ABBREVIATIONS
Table 6
List of abbreviations
Abbreviation
Explanation
CVC
Corporación Autónoma Regional del Valle del Cauca
DAGMA
Departamento Administrativo de Gestión del Medio Ambiente (del Municipio de Cali)
EMCALI
Empresas Municipales de Cali
EPSA
Empresa de energía del Pacífico S.A.
ONI
Oceanic Niño Index
LW-AF20130064
- 30 -
Royal HaskoningDHV
8
COLOPHON
LW-AF20130064
Client
Project
: NL Agency
: Aguablanca Dike along the Cauca River, Cali, Colombia
File
Length of report
Author
Contributions
Internal check
:
:
:
:
:
Project Manager
Project Director
Date
Name/Initials
: Martijn van Elswijk
:
: 31 January 2013
:
BB2984
31 pages
Hans Leenen
Marcella Busnelli, Michel Tonneijck, Steven Sjenitzer, Joop de Bijjl
Erik Arnold
LW-AF20130064
- 31 -
HaskoningDHV B.V.
Laan 1914 no. 35
3818 EX Amersfoort
P.O. Box 1132
3800 BC Amersfoort
The Netherlands
T +31 33 468 2000
F +31 33 468 2801
www.royalhaskoningdhv.com
Royal HaskoningDHV
ANNEX 1
Hydrology
LW-AF20130064
appendix 1
-1-
Royal HaskoningDHV
Table 7
Year
Juanchito hydrometric station: maximum annual level and discharge
Maximum discharge (m3/s) Maximum level (m local reference) Reference level (m.s.l)
Actual level (m.s.k)
1945
674.0
5.08
943.63
948.71
1946
684.0
5.08
943.63
948.71
1947
715.0
5.20
943.63
948.83
1948
676.0
4.95
943.63
948.58
1949
798.0
5.54
943.63
949.17
1950
1,044.0
6.40
943.63
950.03
1951
676.0
4.74
943.63
948.37
1952
710.0
4.88
943.63
948.51
1953
870.0
5.67
943.63
949.30
1954
822.0
5.36
943.63
948.99
1955
822.0
5.30
943.63
948.93
1956
878.0
5.59
943.63
949.22
1957
823.0
5.20
943.63
948.83
1958
647.0
4.55
943.63
948.18
1959
621.0
4.41
943.16
947.57
1960
839.0
5.67
943.16
948.83
1961
622.0
4.40
943.16
947.56
1962
692.0
4.79
943.16
947.95
1963
711.0
4.87
943.16
948.03
1964
688.0
4.64
943.16
947.80
1965
736.0
5.06
943.16
948.22
1966
1,059.0
6.47
943.16
949.63
1967
817.0
5.40
943.16
948.56
1968
749.0
5.06
943.16
948.22
1969
766.0
5.10
943.21
948.31
1970
936.0
5.93
943.21
949.14
1971
1,074.0
6.48
943.21
949.69
1972
792.0
5.11
943.18
948.29
1973
912.0
6.42
942.45
948.87
1974
996.0
6.85
942.45
949.30
1975
950.0
7.01
942.45
949.46
1976
876.0
6.55
942.45
949.00
1977
637.0
5.00
942.45
947.45
1978
770.0
5.74
942.45
948.19
1979
859.0
6.24
942.45
948.69
1980
463.0
3.84
942.45
946.29
1981
791.0
5.86
942.45
948.31
1982
868.0
6.29
942.45
948.74
1983
770.0
5.74
942.45
948.19
1984
1,026.0
7.12
942.45
949.57
1985
619.0
4.69
942.45
947.14
1986
619.0
4.81
942.45
947.26
1987
506.4
3.94
942.45
946.39
1988
943.0
6.40
942.45
948.85
LW-AF20130064
appendix 1
-2-
Royal HaskoningDHV
Year
Maximum discharge (m3/s) Maximum level (m local reference) Reference level (m.s.l)
Actual level (m.s.k)
1989
743.2
5.34
942.45
947.79
1990
560.6
4.38
942.45
946.83
1991
428.0
3.58
942.45
946.03
1992
318.4
2.78
942.45
945.23
1993
760.5
5.83
942.45
948.28
1994
769.5
5.89
942.45
948.34
1995
574.6
4.59
942.45
947.04
1996
726.0
5.63
942.45
948.08
1997
974.2
7.03
942.45
949.48
1998
818.5
6.19
942.45
948.64
1999
991.0
7.25
942.45
949.70
2000
887.2
6.74
942.45
949.19
2001
568.0
4.79
942.45
947.24
2002
694.4
5.58
942.45
948.03
2003
530.6
4.52
942.57
947.09
2004
574.0
4.82
942.57
947.39
2005
636.0
5.23
942.57
947.80
2006
902.8
6.84
942.57
949.41
2007
954.0
7.14
942.57
949.71
2008
1,022.0
7.56
942.57
950.13
2009
786.0
6.16
942.57
948.73
2010
1,007.6
7.48
942.57
950.05
2011
1,148.0
7.94
942.57
950.51
3
Current water level - discharge relation
(from table and fitted equation of third order)
2
y = 0.008x + 6.621x + 83.775x + 15.511
2
R = 0.9998
Table
Formula
[m3/s]
1400
1200
1000
800
600
400
200
0
3
4
5
6
7
8
9
---> water level [m local reference]
Table 8
Current water level – discharge relation from table and fitted equation of third order
LW-AF20130064
appendix 1
-3-
Royal HaskoningDHV
Table 9
H
Juanchito: Current water level – discharge relation (provided by CVC, 14.09.2012)
00
1
2
3
4
5
6
7
8
9
0.10
Q
53.00
53.10
53.20
53.30
53.40
53.50
53.60
53.70
53.80
53.90
0.20
54.00
54.40
54.80
55.20
55.60
56.00
56.40
56.80
57.20
57.60
0.30
58.00
58.68
59.36
60.04
60.72
61.40
62.08
62.76
63.44
64.12
0.40
64.80
65.61
66.42
67.23
68.04
68.85
69.66
70.47
71.28
72.09
0.50
72.90
73.81
74.72
75.63
76.54
77.45
78.36
79.27
80.18
81.09
0.60
82.00
82.80
83.60
84.40
85.20
86.00
86.80
87.60
88.40
89.20
0.70
90.00
90.80
91.60
92.40
93.20
94.00
94.80
95.60
96.40
97.20
0.80
98.00
99.00
100.00
101.00
102.00
103.00
104.00
105.00
106.00
107.00
0.90
108.00
109.00
110.00
111.00
112.00
113.00
114.00
115.00
116.00
117.00
1.00
118.00
118.90
119.80
120.70
121.60
122.50
123.40
124.30
125.20
126.10
1.10
127.00
127.90
128.80
129.70
130.60
131.50
132.40
133.30
134.20
135.10
1.20
136.00
136.90
137.80
138.70
139.60
140.50
141.40
142.30
143.20
144.10
1.30
145.00
145.90
146.80
147.70
148.60
149.50
150.40
151.30
152.20
153.10
1.40
154.00
155.10
156.20
157.30
158.40
159.50
160.60
161.70
162.80
163.90
1.50
165.00
165.90
166.80
167.70
168.60
169.50
170.40
171.30
172.20
173.10
1.60
174.00
175.00
176.00
177.00
178.00
179.00
180.00
181.00
182.00
183.00
1.70
184.00
185.00
186.00
187.00
188.00
189.00
190.00
191.00
192.00
193.00
1.80
194.00
195.10
196.20
197.30
198.40
199.50
200.60
201.70
202.80
203.90
1.90
205.00
206.00
207.00
208.00
209.00
210.00
211.00
212.00
213.00
214.00
2.00
215.00
216.40
217.80
219.20
220.60
222.00
223.40
224.80
226.20
227.60
2.10
229.00
230.00
231.00
232.00
233.00
234.00
235.00
236.00
237.00
238.00
2.20
239.00
240.10
241.20
242.30
243.40
244.50
245.60
246.70
247.80
248.90
2.30
250.00
251.00
252.00
253.00
254.00
255.00
256.00
257.00
258.00
259.00
2.40
260.00
261.00
262.00
263.00
264.00
265.00
266.00
267.00
268.00
269.00
2.50
270.00
271.30
272.60
273.90
275.20
276.50
277.80
279.10
280.40
281.70
2.60
283.00
283.70
284.40
285.10
285.80
286.50
287.20
287.90
288.60
289.30
2.70
290.00
291.50
293.00
294.50
296.00
297.50
299.00
300.50
302.00
303.50
2.80
305.00
306.40
307.80
309.20
310.60
312.00
313.40
314.80
316.20
317.60
2.90
319.00
320.10
321.20
322.30
323.40
324.50
325.60
326.70
327.80
328.90
3.00
330.00
331.10
332.20
333.30
334.40
335.50
336.60
337.70
338.80
339.90
3.10
341.00
342.10
343.20
344.30
345.40
346.50
347.60
348.70
349.80
350.90
3.20
352.00
353.60
355.20
356.80
358.40
360.00
361.60
363.20
364.80
366.40
3.30
368.00
369.00
370.00
371.00
372.00
373.00
374.00
375.00
376.00
377.00
3.40
378.00
379.00
380.00
381.00
382.00
383.00
384.00
385.00
386.00
387.00
3.50
388.00
389.40
390.80
392.20
393.60
395.00
396.40
397.80
399.20
400.60
3.60
402.00
402.60
403.20
403.80
404.40
405.00
405.60
406.20
406.80
407.40
3.70
408.00
410.00
412.00
414.00
416.00
418.00
420.00
422.00
424.00
426.00
3.80
428.00
429.20
430.40
431.60
432.80
434.00
435.20
436.40
437.60
438.80
3.90
440.00
441.80
443.60
445.40
447.20
449.00
450.80
452.60
454.40
456.20
4.00
458.00
459.70
461.40
463.10
464.80
466.50
468.20
469.90
471.60
473.30
4.10
475.00
476.00
477.00
478.00
479.00
480.00
481.00
482.00
483.00
484.00
4.20
485.00
486.50
488.00
489.50
491.00
492.50
494.00
495.50
497.00
498.50
4.30
500.00
501.00
502.00
503.00
504.00
505.00
506.00
507.00
508.00
509.00
4.40
510.00
511.80
513.60
515.40
517.20
519.00
520.80
522.60
524.40
526.20
4.50
528.00
529.30
530.60
531.90
533.20
534.50
535.80
537.10
538.40
539.70
4.60
541.00
541.90
542.80
543.70
544.60
545.50
546.40
547.30
548.20
549.10
4.70
550.00
552.00
554.00
556.00
558.00
560.00
562.00
564.00
566.00
568.00
4.80
570.00
572.00
574.00
576.00
578.00
580.00
582.00
584.00
586.00
588.00
4.90
590.00
591.40
592.80
594.20
595.60
597.00
598.40
599.80
601.20
602.60
LW-AF20130064
appendix 1
-4-
Royal HaskoningDHV
H
00
1
2
3
4
5
6
7
8
9
5.00
Q
604.00
605.60
607.20
608.80
610.40
612.00
613.60
615.20
616.80
618.40
5.10
620.00
621.00
622.00
623.00
624.00
625.00
626.00
627.00
628.00
629.00
5.20
630.00
632.00
634.00
636.00
638.00
640.00
642.00
644.00
646.00
648.00
5.30
650.00
650.90
651.80
652.70
653.60
654.50
655.40
656.30
657.20
658.10
5.40
659.00
661.10
663.20
665.30
667.40
669.50
671.60
673.70
675.80
677.90
5.50
680.00
681.80
683.60
685.40
687.20
689.00
690.80
692.60
694.40
696.20
5.60
698.00
699.20
700.40
701.60
702.80
704.00
705.20
706.40
707.60
708.80
5.70
710.00
712.00
714.00
716.00
718.00
720.00
722.00
724.00
726.00
728.00
5.80
730.00
731.00
732.00
733.00
734.00
735.00
736.00
737.00
738.00
739.00
5.90
740.00
741.90
743.80
745.70
747.60
749.50
751.40
753.30
755.20
757.10
6.00
759.00
761.10
763.20
765.30
767.40
769.50
771.60
773.70
775.80
777.90
6.10
780.00
781.00
782.00
783.00
784.00
785.00
786.00
787.00
788.00
789.00
6.20
790.00
791.20
792.40
793.60
794.80
796.00
797.20
798.40
799.60
800.80
6.30
802.00
804.30
806.60
808.90
811.20
813.50
815.80
818.10
820.40
822.70
6.40
825.00
826.50
828.00
829.50
831.00
832.50
834.00
835.50
837.00
838.50
6.50
840.00
841.80
843.60
845.40
847.20
849.00
850.80
852.60
854.40
856.20
6.60
858.00
860.20
862.40
864.60
866.80
869.00
871.20
873.40
875.60
877.80
6.70
880.00
881.80
883.60
885.40
887.20
889.00
890.80
892.60
894.40
896.20
6.80
898.00
899.20
900.40
901.60
902.80
904.00
905.20
906.40
907.60
908.80
6.90
910.00
912.00
914.00
916.00
918.00
920.00
922.00
924.00
926.00
928.00
7.00
930.00
932.00
934.00
936.00
938.00
940.00
942.00
944.00
946.00
948.00
7.10
950.00
951.00
952.00
953.00
954.00
955.00
956.00
957.00
958.00
959.00
7.20
960.00
961.00
962.00
963.00
964.00
965.00
966.00
967.00
968.00
969.00
7.30
970.00
972.80
975.60
978.40
981.20
984.00
986.80
989.60
992.40
995.20
7.40
998.00
999.20
1000.00
1001.00
1002.00
1004.00
1005.00
1006.00
1007.00
1008.00
7.50
1010.00
1012.00
1014.00
1016.00
1018.00
1020.00
1022.00
1024.00
1026.00
1028.00
7.60
1030.00
1032.00
1035.00
1037.00
1040.00
1042.00
1045.00
1047.00
1050.00
1052.00
7.70
1055.00
1057.00
1060.00
1062.00
1065.00
1067.00
1070.00
1072.00
1075.00
1077.00
7.80
1080.00
1082.00
1085.00
1087.00
1090.00
1092.00
1095.00
1097.00
1100.00
1102.00
7.90
1105.00
1107.00
1110.00
1112.00
1115.00
1117.00
1120.00
1122.00
1125.00
1127.00
8.00
1130.00
1131.00
1132.00
1133.00
1134.00
1135.00
1136.00
1137.00
1138.00
1139.00
8.10
1140.00
1141.00
1142.00
1143.00
1144.00
1145.00
1146.00
1147.00
1148.00
1149.00
8.20
1150.00
1152.00
1154.00
1156.00
1158.00
1160.00
1162.00
1164.00
1166.00
1168.00
8.30
1170.00
1172.00
1174.00
1176.00
1178.00
1180.00
1182.00
1184.00
1186.00
1188.00
8.40
1190.00
1192.00
1194.00
1196.00
1198.00
1200.00
1202.00
1204.00
1206.00
1208.00
8.50
1210.00
1212.00
1214.00
1216.00
1218.00
1220.00
1222.00
1224.00
1226.00
1228.00
8.60
1230.00
1232.00
1234.00
1236.00
1238.00
1240.00
1242.00
1244.00
1246.00
1248.00
8.70
1250.00
1252.00
1254.00
1256.00
1258.00
1260.00
1262.00
1264.00
1266.00
1268.00
8.80
1270.00
1272.00
1274.00
1276.00
1278.00
1280.00
1282.00
1284.00
1286.00
1288.00
8.90
1290.00
1292.00
1294.00
1296.00
1298.00
1300.00
1302.00
1304.00
1306.00
1308.00
9.00
1310.00
LW-AF20130064
appendix 1
-5-
Royal HaskoningDHV
Moment Ratio Diagram
Gumbel
Weibull
LP3
Observed
LN2
Normal
Gamma
Logistic
30
Ck (Kurtosis coefficient)
25
20
15
10
5
0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
Cs (Skewness coefficient)
Figure 9
Moment-ratio diagram of observed extremes and theoretical probability distributions
Note: For a given distribution, conventional moments can be expressed as functions of the parameters of
the distributions. It follows that the higher order moments can be expressed as functions of the lower order
moments. Figure 9 presents the moment-ratio diagram of the Skewness coefficient en the Kurtosis
coefficient for a number of well known distributions, as well as for the observed values of the maxima of
the Rio Cauca at Juanchito (the blue dot). For some of the distribution functions the ratio follows a curve,
for others it is a distinct point in the graph. This merely is a characteristic of the particular distribution. The
figure shows that the Skewness-Kurtosis ratio for the observed values practically coincides with the
theoretical value for the LP3 distribution. Furthermore it shows that the Skewness-Kurtosis ratio for the
Gumbel distribution is far off the ratio of the observed values. The conclusion is that the momentcharacteristics of the observed values correspond much better with the LP3 distribution than with the
Gumbel distribution.
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ANNEX 2
Longitudinal dike profiles and hydrodynamic modelling results
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Crest level of Jarillón Agua Blanca and calculated water levels + required freeboard
Level [msnm]
956
955
954
water level T=10
water level T=25
water level T=100
water level T=250
water level T=500
dike crest level
original design T=10 + 2,50
953
952
951
950
949
948
Juanchito
km 139 + 259 m
Canal Sur
km 127 + 724 m
Rio Cali
km 146 + 300 m
147
146
145
144
143
142
141
140
139
138
137
136
135
134
133
132
131
130
129
128
127
947
Perfil longitudinal de la corona del dique de la margen izquierda del Canal Interceptor Sur
Perfil longitudinal de la corona de los diques del Río Cali
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Figure 10
Inundation modelling
Location of breaching
Scenarios return period 1/100 years
Location No. 6
Location No. 5
Location No. 4
Location No. 3
Location No. 2
Location No. 1
Breaching in all the locations
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Location No. 2
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Location No. 4
Location No. 5
Location No. 6
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ANNEX 3
Hydrodynamic modelling, methodology
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Calibration of the model
The model was recalibrated to fit the water level at the station Juanchito for the different return periods.
The roughness coefficient in the main channel was tuned. Furthermore the bathymetry at the right margin,
where the data is less accurate, was adjusted. The water levels in the station Juanchito for the different
return periods were reproduced with an error of approximately 10 cm. Besides the water levels at a
location upstream of the station Juanchito were compared with the values obtained from the hydrological
analysis of the data of the station Juanchito and the translation to locations upstream and downstream by
applying the water slopes calculated with a 1D-model [4]. The maximum difference calculated is about 10
cm.
Modelling of the flooding scenario’s
In order to simulate the flooding scenario’s the boundary conditions upstream and downstream were
defined.
Upstream the flood hydrograph was defined on the basis of the measured hydrograph in 2011. For every
return period a flood hydrograph is obtained. These flood hydrographs are shown in Figure 11.
Downstream the water levels were obtained from the Q-h relation in Juanchito and after that they were
extrapolated to the location downstream. These water levels are shown in Figure 12.
The locations of overtopping were modelled as a change in the bathymetry. To our knowledge it is not
possible to include in the CCHE2D model constructions such as weirs (sub-grid modelling of
constructions). Due to that fact, the grid has been refined to reproduce the height of the dike.
Figure 11
Upstream boundary condition
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Figure 12
Downstream boundary condition
Recommendations
There are uncertainties in the numerical modelling but also in the data. Monitoring of water levels and
discharges should be continued. We advise to include more measurement locations, upstream and
downstream station Juanchito. Furthermore it is important to determine for which levels flooding have
occurred upstream Juanchito because this flooding has influence on the water levels and discharges in
station Juanchito.
The following recommendations are given concerning the hydrodynamic model in order to improve the
accuracy of the modelling results:
1. Update the digital elevation data to improve the model results. The bathymetry to the right margin
should be included. Furthermore mainly due to human actions the bathymetry of the main channel and
floodplains might have changed and needs to be updated.
2. Develop an integrated hydrodynamic model of the river Cauca starting at Salvajina reservoir. In this
model the overtopping and flooding should be included. The model should be calibrated in order to
reproduce the last flooding events for instance by comparing the inundated area with aerial
photographs. These simulations will give more insight in the discharges through the river Cauca since
also overtopping and flooding would be included. We understand that this model will be constructed in
another project [5]. We advise the local team to participate in this study so that the experience gained
in the modelling of the river Cauca along the city of Cali can be shared, in order to improve the
modelling system.
3. In choosing the numerical model, we recommend that constructions such as weirs and roads be
accurate schematized.
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Considerations concerning fluvial morphodynamics
During the study and conversations with the local team some morphodynamic issues arose. Amongst
these issues we list the following:
1. Local erosion: for instance in the location “Nuevo Amanecer” erosion in the left margin has occurred
probably as result of a bank protection carried out at the right margin.
2. Bank erosion related to natural meandering of the river may affect the stability of the dikes.
3. Dredging activities (illegal) are carried out in this part of the river Cauca. These dredging activities may
lead to erosion of the river bed. However there is no clear indication of large scale erosion of
sedimentation of the river Cauca.
4. The construction of the Salvajina reservoir will have had an influence on the morphological
developments of the river Cauca due to the changes in the discharges and sediment loads.
5. There are indications of changes in discharges and sediment load in the Canal Interceptor del Sur due
to human activities such as deforestation that may also have influence on the morphological
developments of the river Cauca.
6. The bed in some parts consists of a hard soil deposit (mixture of clay, silt and sand), which is in Cali
called “Caliche”. Due to this soil the bed level has remained rather stable. Between this hard soil, there
is sand that can be eroded. Local erosion occurs in those sections.
We recommend that the fluvial morphodynamics of the river Cauca be studied in order to have a better
understanding of its morphodynamics and the influence of the human activities on the morphological
developments. We have the following recommendations:
1. Monitoring the bed evolution of longitudinal profiles of the main river. Is there a trend (erosion,
sedimentation of stable) in the bed level?
2. Monitoring bank erosion since it might influence the stability of the dikes and banks.
3. Obtain information over the soil and subsoil of the main river. Critical locations are where a sand layer
in the subsoil may be cut by ongoing erosion. Such locations ask for more extensive monitoring.
4. Obtain information of the dredging activities: dredging site, dredged volumes, properties of the dredged
material.
5. Prepare a plan for managing the bed levels where also dredging activities are carried out in a control
manner, by defining where it is possible to dredge and how much. Geotechnical stability of dikes and
banks needs to be guaranteed, and therefore the riverbed should not incise too much. Such demands
to the riverbed require that the river manager needs to assess the development of the bed and to
intervene in the river system if necessary.
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ANNEX 4
Flood risk management methodology
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Concepts
The word risk refers in general to the probability of loss or harm. In the context of flood risk management it
denotes the combination of the probability of a flood and its consequences. In this context also the terms
hazard and vulnerability are often used. Hazard refers to the source of danger, i.e. the probability of
flooding. Vulnerability relates to potential consequences in case of an event [6].
Integrated flood risk management is an approach to identify, analyze, evaluate, control and manage the
flood risks in a given system. Figure 13 presents a general scheme for flood risk management. The
following steps are defined:
● Definition of the system, the analyzed hazards and the scope of the analysis.
● A quantitative analysis where the probabilities and consequences are assessed and
combined/displayed into a risk number, a graph or a flood risk map.
● Risk evaluation: with the results of the former analysis the risk is evaluated. In this phase the decision
is made whether the risk is acceptable or not.
● Risk reduction and control: dependent on the outcome of the risk evaluation, measures can be taken in
order to reduce the risk. Measures could concern structural and non-structural measures. It should also
be determined how the risks can be controlled and managed, for example by monitoring, inspection or
maintenance.
The scheme focuses on minimization of flood risks to an acceptable level. The approach could also be
used to assess the overall hydrological performance of the system (e.g. minimization of drought,
maximization of water quality and ecological quality). Then the approach will focus on multiple objectives:
not only to minimize the risk, but also to maximize the performance.
Figure 13
General scheme for flood risk management
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Approach for economic damage assessment
Scope of the analysis
The scope and level of detail of the damage evaluation has been defined on the basis of the spatial scale
of the study and the availability of data. Due to the fact that very precise methods require more effort (i.e.
time and money) than less detailed approaches and that the resource are usually limited, the most precise
methods are often restricted to small areas under investigation, while studies with a research area of
regional or even national size mostly have to rely on less detailed methods.
The area of the study is the flood area of the city of Cali, at the left margin of the river Cauca between
Canal Interceptor del Sur and the river Cali. At the right margin of the river Cauca lays the city of
Calendaria, where there is no bathymetric information available for the study.
In this study we focus on the priced direct damages. This category of damage constitutes the largest part
of the total damage. For example in the standardized damage method that is used in the Netherland the
following main damage categories are considered: land use, infrastructure, households, companies and
other. Within each main categories, sub-categories are distinguished (e.g. agriculture, urban area, or
recreation within the main category land-use).
Direct damage assessment
Methods for the estimation of the direct economic damage to objects, such as structures, houses are well
established, and the use of so-called damage functions is widespread ([7], [8], [9], [10]).
The procedure for the estimation of direct physical damages [12] is illustrated in Figure 13. The procedure
comprises three main elements:
Determination of flood characteristics
Assembling information on land use data and maximum damage amounts
Application of stage-damage functions.
We describe these elements in more detail below.
Determination of flood characteristics
Flooding patterns are in general simulated with a two dimensional hydrodynamic model. The existent 2Dmodel of the University of Mississippi of the river Cauca between the Canal Interceptor Sur and the river
Cali was applied for this study. This model was recalibrated since the statistics of discharges and water
levels was updated in this study. The water levels in the station Juanchito for the different return periods
were reproduced with an error of less than 10 cm. The model runs were carried out by Angela Cabal of the
corporation OSSO (local partners in Colombia). A complete description of the model is given in [3]. The
model has some limitations but there are also restrictions on the available data mainly in the flooding area.
For instance there is not information of the bathymetric on the right margin of the river Cauca and therefore
the inundation of the city Candelaria is not included.
In this study we applied the existent 2D-model and we made recommendations for a more accurate
modelling system and for the required data collection for future studies.
The hydrodynamic model provides insight in flood characteristics, such as water depth, flow velocity and
the rate at which the water rises. All these characteristics can be depicted on a map.
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Flood risk assessment
Definition
In the risk assessment the results of hazard and damage assessments are combined. Flood risk is
generally defined as follows:
Risk = Probability x Damage
For example, if an area has a probability of flooding of 1% per year (or 1/100 per year) and the damage is
100 million COP, the risk equals 1 million COP per year. As this risk number reflects the average expected
economic damage per year, it is also referred to as yearly expected economic damage.
The flood scenarios can be defined depending on their return period, i.e. the average recurrence interval
between the occurrence of two floods with a certain flood level and corresponding damage value. It is also
possible to determine the probability of exceedance of an event with certain damage. That is the
probability (per year) that a certain damage value will be exceeded so that:
Probability of exceedance = 1 / return period
This means that the event a 100 year return period has a probability of exceedance of 1/100 per year.
Economic optimization
The economic optimization approach is applicable to determine an optimal level of protection when
investments in the protection and the risk are dependent on the level of protection. This is for example the
case for flood prone areas that are protected by dikes. In that case the decision problem becomes the
choice of the height of the dikes and thus the choice for the protection level that de dikes provide.
According to the method of economic optimization, the total costs in a system are determined by the sum
of the expenditure for a safer system and the expected value of the economic damage. In this economic
optimization the incremental investments in more safety are balanced with the reduction of the risk. The
investments consist of the costs to strengthen and raise the dikes. In a simple approach it is assumed that
flooding could only occur due to overtopping of the flood defences. Thereby each dike height corresponds
to a certain probability of flooding (the higher the dikes the smaller the probability of flooding) and an
associated damage. By summing the costs and the expected damage or risk, the total costs are obtained
as a function of the safety level. A point can be determined where the total costs are minimal, the so-called
optimum (Figure 14). In the optimum the corresponding dike height is known. Because the statistics of the
water levels are also known, the corresponding protection level in terms of a probability can be defined.
The economic optimization approach was applied to flood protection systems by the Delta Committee in
the Netherlands. This Committee investigated possibilities for new safety standards after a major flooding
caused enormous damage in the Netherlands in 1953. Eventually these results have been used to derive
safety standards for flood defences in the Netherland. For coastal areas protection has been chosen with
exceedance probabilities of 1/4,000 per year and 1/10,000 per year. For the Dutch river areas the safety
standards were set at 1/1,250 per year and 1/2,000 per year.
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Figure 14
Principle of economic optimization
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ANNEX 5
Field assessment of the conditions of the Aguablanca dike
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Introduction
th
Three dike visits were made. On Wednesday 19 of September a boat visit was made followed by an dike
visit by car on Thursday 20th of September. On Tuesday 2nd of October a final visit has been made to the
pumping station Paso del Comercio and the PTAR (drinking water treatment plant).
The objective of these visits was to have a visual inspection of the physical condition in general and of the
envisaged problems at two structures in particular. As a general observation we conclude that the dike is
deteriorated by lack of maintenance, sewerage systems and roads that cross the dike, and ant invasions
and tree roots. Later on the constructions through the dike were studied and geotechnical calculations
done. The inspection is documented by photos and technical information. The main goal of the inspection
was to locate the weakest spots and to make an inventory of the most needed and effective short term
measures.
Boat visit (Wednesday 19th of September) and dike visit (Thursday 20th of September)
The inspections of the dike resulted in 8 points of attention
1.
Debris dumping
There has been a lot of debris dumping on riverside of the dike. This dumping of debris becomes an
obstacle for the river during a flood and will raise the water level. It is therefore important to stop illegal
dumping of debris.
Cali acknowledges the problem and has already started with the removal of the debris, but the
problem continues. It is recommended to search for alternative dumpingsites. Debris does not have to
be a waste material, but can be used as base material. Therefore a debris crusher instalation is
needed.
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2.
Crest level
Historic information by Hidro-Occidente (Guillermo Regalado) provides the following:
When the Aguablanca dike was designed in 1957, the consultants only had 10 years of data available.
With these data they estimated the maximum of those years to have a return period of 10 years. They
also estimated that with a freeboard of 1.0 m, the crown of the dike could manage a water level
corresponding with a return period of 100 years. An important issue, confirmed by Ingeniero Jorge
Llanos, who participated in the studies, is that during construction of the dike, another 1.5 m was
added to the crown level, corresponding with a return period of 100 years. It thus follows that the dike
was constructed with a freeboard of 2.50 m above the level of a return period of 10 years.
(Original communication by Guillermo Regalado:
Los consultores, con los pocos datos existentes (1946-1957) estimaron que la creciente de los años
50 tenía un Tr de 1 en 10 años. Estimaron también que si se adoptaba un borde libre de 1.0 m el
nivel del agua, coincidiendo con el nivel de la corona o cresta del dique, podría manejar una creciente
de Tr= 1 en 100 años.
Algo muy importante, confirmado con el ingeniero Jorge Llanos que estuvo en el proceso de estudios,
es que para construcción se incrementó en 1.5 m el nivel del dique con relación al nivel del agua
adoptado para una creciente de 1 en 100 años (ver punto C, página 4 del informe de los consultores
Kirpich y Hadjiluokas). Ese incremento se realizó; es decir que con relación a los niveles de agua de
1 en 10 años (creciente de los años 50), la corona o cresta del dique quedó construida con un borde
libre (freeboard) de 2.50 m)
Nivel_TR10
Nivel_TR25
Nivel_TR100
Nivel_TR250
Nivel_TR500
Dike level
Level [msnm]
956
955
954
953
952
951
950
949
948
Juanchito
km 139 + 259 m
Canal Sur
km 127 + 724 m
Rio Cali
km 146 + 300 m
147
146
145
144
143
142
141
140
139
138
137
136
135
134
133
132
131
130
129
128
127
947
Figure 15
Longitudinal profile of the Aguablanca dike based on direct field monitoring, and
water levels corresponding with different return periods
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3.
Hydraulic constructions
During the dike inspection it was noticed that a few construction show damage and some other
constructions can potentially cause damage in the future. The constructions are mostly owned by
corporations or parties that are not primary responsible for the safety of the dike.
The construction which shows the most damage is the pumping station Paso del Comercio. An extra
visit was made at this construction on Tuesday 2nd of October.
4.
Land side slope is steep
The slope of the dike on the land side is mostly between 1:1.5 (66%) and 1:2 (50%). Considering
safety requirements of T = 100 or better the slope is considered to be quite steep.
It is recommended to create a gentler slope on the land side of the dike. For an optimum slope,
geotechnical calculations have to be made. In the Netherlands often a minimum slope of 1:3 (33%) is
used. This has a lot of positive effects:
•
maintenance of a 1:3 slope is better, damage of people, animals is less probable
•
a gentle slope will better resist overflowing or overtopping water (erosion control)
•
where a thin cohesive top layer and short distance to the river coincide, land side slope
stability and piping is more of a problem. A more gentle slope will accomplish more safety
on these failure mechanisms
•
earthquake induced liquefaction will yield less damage for gentler slopes
5.
Animal activity
During the dike inspection it has been noticed that there is a lot of activity of ants. These ants cause a
lot of damage by digging holes in the dike. These holes can cause water transportation through the
dike followed by erosion of the dike.
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It is recommended to exterminate ant activity as much as possible. Therefore the following activities
are needed:
•
Implement consequent monitoring of ant activity and anthills (e.g. every month)
•
maximum intervention level of displaced soil, e.g. 50 to 100 liters
•
filling of anthill cavities, preference bentonite
•
consequent killing of ants
6.
Earthquake and flood
It is not probable that an earthquake and a flood coincide. However, one may take into account that a
flood might come within a year after a major earthquake. Considering that a major earthquake might
induce liquefaction, resulting in serious dike deformation, it is recommended to identify potential
liquefiable areas and limit the problem.
7.
Housing and trees on the dike
It has been noticed that housing and trees cut into essential minimum design profile. This makes the
dike more vulnerable for stability and piping problems.
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It is recommended to
•
work with theoretical minimum design profile (fulfilling height and stability requirements)
•
when dike is wider (over dimensioned), houses need to be outside theoretical minimum
profile
•
dead trees should be removed, including the root system
8.
Dike inspection plan
At the start of the project no coherent dike inspection plan was available. It is very important to make
sure that the people who will be executing the inspections will have the same base and points of
focus. A inspection plan has been written in Spanish which can be used to execute the inspection in
the direct future. The inspection plan was presented during a work shop on September 27 and is
attached in Annex 7.
Visit dike constructions October 2nd
After the first dike inspections it appeared there were some concerns with the constructions in the dike.
Therefore an extra visit was held to the pumping station Paso del Comercio and the drinking water
treatment plant (PTAR).
Pumping station Paso del Comercio
The pumping station Paso del Comercio is the bigger one of the 2 pumping stations of Cali. It is situated in
the lowest part of the city. This makes it a very important pumping station that is essential for controlling
the water level in the city of Cali.
The construction has 4 different units:
•
The most Northern unit is a gravity outlet (G)
•
South of the gravity outlet is pumping unit 2 (2)
•
South of pumping unit 2 is an emergency pumping unit (E)
•
The most southern is pumping unit 1 (1)
G
2
1
E
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In 2010 and 2011 river levels were extremely high resulting in various damages that were observed. Wells
with transportation of soil were observed on the water side of the pumping station. This means that there is
a hydraulic connection between the land side and the riverside of the dike. Not only is it possible that the
water flows from the land side to the riverside. The other way around is possible as well. Emergency
measures were taken and the gravity outlet has been shut down by building a closing dike on the river side
of the outlet. At the moment a floating pumping unit is in place to pump water from the gravity outlet tot the
riverside outlet of pumping unit 2. In our opinion, this supposedly temporary construction will be used for a
longer time.
During the floods major damage caused by erosion developed at the riverside outlet of pumping unit 2.
The damage occurred 2 years ago and is worsening ever since and will keep on worsening in the future if
no measures are taken.
The
emergency
outlet has had
some problems during the river flood as well. The water outlet pipe has no closing system on the river side.
During the flood, the pipes were filled with water causing some leakage through the concrete construction
on the landside of the dike.
The most southern pumping unit is pumping unit 1. This unit had the same kind of problems as pumping
unit 2. Emergency measures were taken by putting a lot of soil in the water outlet of this unit. The problem
of this measure is that the water has no free outflow. This can cause problem if maximum capacity is
needed. Another risk is formed by the broken valves on the river side of outlet pipe. At flood level on the
river this will cause unnecessary water pressure on the pipe and land side construction. At the moment
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EMCALI only relies on the valves on the inside of the pipes. This is a situation that poses an unnecessary
risk. Immediate action is required to repair / replace these broken valves
Drink water treatment plant
During the visit of the water treatment plan, it was explained that there was no risk of inundation of the land
behind the dike, but the top level of the treatment plan is lower than the level of the dike behind the
treatment plant. During the flood the water almost got into the pumping pit. This would have caused the
plant to stop working.
Plans are made to make a concrete wall on top of the plant on the water side. On both side sheet pilings
are planned to connect the structure to the dike. At the downstream side this will be on a distance of circa
20 meters and will provide an gentle transition construction. This appears to be a good solution. On the
upstream side of the plant a sheet pile of circa 200 meters is planned. The reason for this, is an existing
problem with erosion in the river bent. First impression of this solution is that this is an expensive solution.
It is likely that less expensive solutions are available, for instance with enforcement of the rockfill with
asphalt.
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ANNEX 6
Structural stability and analysis of failure mechanisms
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Macro stability, micro stability and land side dike slopes
The stability of the dike on the landside is most vulnerable during flood periods. This is caused by the
combination of high external water pressures on the dike that have to be resisted and high internal water
pressures in the dike, that causes lower effective stresses and therefore lower shear stresses of the soil in
the dike. This makes the dike more vulnerable for slope instability.
To make a good stability analysis a thorough soil investigation is needed together with monitoring of
groundwater levels. Although soil investigation was done, the number of strength parameters test was
insufficient for a thorough stability analysis. To come to a judgment of the slope stability a quick analysis
was made with the slope stability software D-GeoStability.
We recommend to do more triaxial tests on undisturbed clay samples of the dike body to gain a better
insight into the strength parameters along the profile of the Aguablanca dike. We suggest to do at least
one boring per kilometre.
Stability analyses preformed
In the analyses the impact of variations in the strength parameters, width of the outer berm and thickness
of the top-layer on the land side of the dike are examined. For the calculation the parameters below have
been applied.
Strength parameters
Strength parameter based on limited number (6) of provided triaxial tests
Material
cohesion
Sand, medium dense coarse grain
0 kPa
0 kPa
Sand, fine grain
0 kPa
Clay, high void ratio, high plasticity
0.2 kPa
Sand, fine grain (bit loamy)
0 kPa
0 kPa
phi
33.7 ̊
33.7 ̊
35.5 ̊
21 ̊
29 ̊
33.7 ̊
Assumptions strength parameter based on Dutch standards (NEN6740)
Material
cohesion
Sand hard dense, coarse grain
0 kPa
Sand, loose dense, fine grain
0 kPa
Clay (soft)
2 kPa
Clay (medium)
10 kPa
phi
35 ̊
30 ̊
17.5 ̊
17.5 ̊
Strength parameters used in calculations
Material
Sand, medium dense, coarse grain
Sand, fine grain
Clay
phi
35 ̊
30 ̊
21 ̊
cohesion
0 kPa
0 kPa
2 kPa
Hydraulic loads
Water level river: dike crest level
Water level landside 0.50 meter below ground level
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Water level sand layer: crest level dike on outside riverside of the dike decreasing with a slope of 1:20 in
the direction of the landside of the dike with a minimum of 0.5 meter below ground level
Geometry
Geometry of the dike: based on a drawing without date or identification (provided by the local authorities)
Calculation results
Description
Most conservative situation:
Stability sufficient with thick top layer
Stability sufficient with strong top layer
Stability sufficient with wide river side
bank
Parameters
Thickness of the top clay layer = 2 meter
weight top clay layer = 14 kN/m3
Strength top clay layer = c=2 ; phi=17.5 ̊
wideness river side bank = 8 meter
Thickness of the top clay layer = 6 meter
Result
SF=0.7
Cohesion clay = 6
Weight clay = 16
Wideness river side bank = 38 meter
SF=1.0
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SF=1.0
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Figure 16
Schematic representation of calculation
Conclusions:
There are 3 parameters that have a big influence on the dike stability.
• Thickness of the top clay layer on the landside of the dike
• Strength parameters of the top clay layer on the landside of the dike
• Length of the wideness of the river side bank
Heave, sand boil and piping and seepage
The safety of the dike on the fail mechanism piping (backward erosion) is influenced by mostly 2 important
parameters.
1. Width of the outer bank
2. Thickness of the top clay layer on the landside of the dike
If the outer bank is wide, the length of the potential pipe will be too long and no backwards erosion can
develop. For the conditions along the River Cauca this mean that if the outer bank is 45 meter wide no
piping can develop.
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Royal HaskoningDHV
If the top clay layer is thick the pipe is not able to break through the top layer and no backward erosion
can develop either. For the situation along the River Cauca no piping can develop if the top layer has a
minimum thickness of 4.0 meter.
Piping analysis
Use the formula of Bligh (Dutch method)
Width outer bank
variable meter
Width outer slope
8 meter
Width crest
8-60 meter
6 meter
Width inner slope
6.5 meter
Total piping length (L)
20.5 meter
Thickness clay layer landside of the dike (d)
variable meter
kN/m
2-6 meter
3
Mass of clay layer
14
Creep-factor ( C )
18 (see tabel above)
Ground level landside of the dike
0 meter
Maximum water level river
4 meter
Water level difference (∆H)
4 meter
(crest level)
Width outer bank
Thickness clay layer landside
2
3
4
5
6
8
Fail
Fail
Good
Good
Good
10
Fail
Fail
Good
Good
Good
15
Fail
Fail
Good
Good
Good
20
Fail
Fail
Good
Good
Good
25
Fail
Fail
Good
Good
Good
30
Fail
Fail
Good
Good
Good
35
Fail
Fail
Good
Good
Good
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40
Fail
Good
Good
Good
Good
45
Good
Good
Good
Good
Good
50
Good
Good
Good
Good
Good
55
Good
Good
Good
Good
Good
60
Good
Good
Good
Good
Good
Liquefaction and deformations
No calculations on this failure mechanism were made. Although failure of the dike due to liquefaction is
possible when an major earthquake occurs, the probability of a major earthquake coinciding with an
extreme flood event is negligible as compared to the probability of occurrence of a major earthquake
alone.
Erosion control and slope revetment
During conversations with local authorities the erosion of the rockfill has been mentioned. Although locally
this may be a problem, in general the river has a good protection against erosion. This conclusion is based
on the dike visits that were made. If enforcement of the rockfill is necessary, this can be done by applying
asphalt to the rockfill.
Macro stability river side slope
No analyses were done on the stability of the riverside slope. The reason is that the stability of the
riverside slope is only a problem during a quick drop of the water level on the river. If this is the case, there
is no danger for inundations.
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ANNEX 7
Inspection plan
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PLAN DE INSPECCIÓN DE DIQUES
Una guía para:
•
•
•
•
•
Joop de Bijl
Michel Tonneijck
Hans Leenen
mantenimiento
vigilancia
prueba de inundaciones
evaluación a los requisitos de ley
inspección durante un nivel extremo
Waterschap Aa en Maas
Royal HaskoningDHV
Royal HaskoningDHV
Version 27 septiembre 2012
1.
INTRODUCCCION Y PROPOSITO
El Plan de Inspección del Dique describe el proceso de inspección, la aplicación de todas las etapas
del mismo la planeación del mantenimiento y medidas de rehabilitación sugeridas durante el proceso
de diagnostico.
El marco para el plan de inspección son las leyes, reglamentos, políticas e instrumentos
Las inspecciones tienen su fundamento en la Ley del Agua de Holanda, en reglamentos y en políticas
establecidas. Directrices tanto nacionales como locales están disponibles para la implementación de
las inspecciones.
Las siguientes herramientas son necesarias para la implementación de las tareas de inspección.
• Ley de Aguas, establece el marco legal para la entidad que ejerce autoridad sobre el dique
• Reglamento (decreto),determina las reglas aplicables por la autoridad del agua, (Anexo 1)
• Mapa base. Establece las características espaciales y funcionales del dique. En conjunto con
el reglamento representa la base legal para las tareas ejecutadas por la autoridad del agua o
del dique (Anexo 1)
• Plan de manejo del dique. Este plan traduce las políticas nacionales y regionales, las leyes y
regulaciones para el área de gestión. Es la base de todas las actividades de manejo:
inspección, concesión de licencias, mantenimiento, mejoras y ensayos;
• Plan de manejo de inundaciones. Este plan describe el monitoreo de las inundaciones, las
etapas de escalamiento del monitoreo del dique (situación de inundación) y las actividades de
inspección del dique y de la organización asociada. (Anexo 1)
OBJETIVO DE LAS INSPECCIONES
El plan de inspecciones multipropósito
1. Mantenimiento del dique
2. Vigilancia de la integridad del dique: garantizar el cumplimiento del reglamento y del mapa
base, incluido el cumplimiento de las condiciones asociadas a permisos emitidos.
3. Dique a prueba de inundaciones: controlar si el dique, incluyendo las estructuras que lo
cruzan (considerando procedimientos de cierre de válvulas y compuertas) se encuentran en
condiciones aptas para la temporada de inundaciones.
4. Evaluación del dique requerida por ley. Determinación de la altura y resistencia actual de
las estructuras de defensa contra inundaciones, con respecto a condiciones hidráulicas de
frontera actualizadas cada 6 años
5. Inspección del carillón durante inundaciones y medidas de emergencia asociadas.
Figura 1 Falla de estabilidad
2
2.
LAS OPCIONES DE INSPECCIÓN
1. INSPECCION DE MANTENIMIENTO
Mantenimiento reducido tiene el objetivo de extender la vida útil del dique y la prevención de
nuevos daños. Información sobre todas las categorías de dique se establecen para
determinar las medidas de mantenimiento. En particular se trata del registro de la condición
de resistencia a la erosión del revestimiento en grama del dique, de cualquier daño del dique
y de las condiciones operacionales de los mecanismos de cierre de estructuras hidráulicas.
Esta inspección usualmente se realiza después de la temporada de invierno.
El plan de mantenimiento puede ser elaborado con base en la información obtenida en esta
etapa. El monitoreo de la ejecución del mantenimiento hace parte de esta inspección.
2. INSPECCIÓN SOBRE EL CUMPLIMIENTO DE LAS REGLAS
Situaciones ilegales se determinan durante una “inspección de cumplimiento”. La información
requerida es un inventario de acciones ilegales en contra del reglamento estatutario y el
incumplimiento de obligaciones de mantenimiento. El requisito de información se define en
estrecha colaboración con el Departamento de Cumplimiento.
La frecuencia de inspección depende en parte de la intensidad de las violaciones. Al menos
se debe llevar a cabo una vez al mes, de lo contrario se generan derechos adquiridos debido
a la tolerancia demasiado duradera.
A partir de la aplicación del cumplimiento de las reglas se pueden requerir medidas
necesarias para restaurar la condición original del dique.
Figura 2
¿¿¿Cumplimiento de las reglas???
3. INSPECCIÓN ANTES DE LA EPOCA INVERNAL
Se debe inspeccionar la capacidad de retención de agua de los diques antes de las temporadas
de invierno. El desempeño de los mecanismos de cierre de las estructuras en los diques son
probados mediante ensayos de cierre. En los Países Bajos hay una temporada de inundaciones
al año, en Cali dos.
3
Figura 3 Daño de hormigas
4. EVALUACIÓN DEL DIQUE TENIENDO EN CUENTA TODOS LOS MODOS DE FALLA
Los perfiles hidráulicos utilizados para el diseño del dique deben ser actualizados cada 10 años.
Todos los factores que generan modificaciones deben ser incluidos en la evaluación:
• Cambios en el río y en las planicies de inundación que afecten los niveles de agua
• Efectos del cambio climático
• Mayor demanda de protección contra inundación a causa de rápido desarrollo espacial y
económico en el área protegida
En este proceso todos los modos de falla son reconsiderados. Esta evaluación puede llevar a
concluir que el carillón necesita refuerzo, en ese caso se haría necesario un programa de
reconstrucción del dique.
4
5. INSPECCIÓN DURANTE INUNDACIONES
El dique debe ser inspeccionado durante eventos de nivel alto del río.
El dique debe ser reparado o reforzado inmediatamente en caso de identificarse una
condición de colapso inminente.
Figura 4 Inundación
5
3.
INSPECCIÓN
Observaciones durante la inspección tienen por objetivo capturar ciertas características de un
dique relacionadas con su estado de mantenimiento y el estado de la seguridad del mismo
(integridad).
3.1 PROPÓSITO
El propósito de la observación es la detección, identificación y registro de ciertas características
del dique.
3.2 MÉTODODEOBSERVACIÓN
Identificarlas técnicas de inspección y observación a ser utilizadas, por ejemplo:
Inspección visual
La observación visual es la esencia de las inspecciones. Un inspector experto puede juzgar las
características importantes del dique de un vistazo. Es difícil que los resultados de esta
inspección sean los mismos que los de un colega. Las observaciones visuales se basan en gran
parte en el conocimiento y la experiencia personal y por lo tanto tienen un carácter subjetivo.
Para garantizar que las inspecciones visuales sean tan objetivas como sea posible, es importante
asegurarse que los inspectores sean entrenados para reconocer y clasificar los elementos
observados.
Técnicas instrumentales de inspección
Las inspecciones no se limitan a observaciones visuales. Las mediciones son cada vez
importantes en las inspecciones. Esto se refiere no sólo a mediciones de la altura de la cresta del
dique(GPS, nivelaciones, altimetría láser, monitoreo remota), sino también a la medición de los
parámetros en los diques.
Figura 5
Fuente de arena, indicación del inicio de tubificación
6
3.3
HOJA DE RUTA PARA LA INSPECCIÓN DEL DIQUE
PASO 1:
DETERMINAR QUE SECCIÓN DE DIQUE SE VA A INSPECIONAR Y DEFINIR EL MÉTODO DE
INSPECCIÓN
En este caso, la elección debe hacerse a partir de las siguientes categorías:
• Inspección de mantenimiento
• Inspección sobre el cumplimiento de las reglas
• Inspección de capacidad de resistencia a inundaciones
• Evaluación global del dique
• Monitoreo y reparación de emergencia durante inundaciones
PASO 2:
DETERMINAR LA CALIDAD Y CLASIFICACIÓN DE URGENCIA DE LAS OBSERVACIONES
(Cuadros 3.1 y 3.2)
CUADRO 3.1 CLASIFICACION DE CALIDAD
Grado
Bueno
Raonablemente
suficiente
Pobre
Malo
Descripción
El elemento cumple a cabalidad con los requerimientos
estructurales y de funcionalidad
El elemento cumple con los requerimientos estructurales y de
funcionalidad
El elemento no cumple con suficiencia con los requerimientos
El elemento no satisface ninguno de los requerimientos
TABLE 3.2 CLASIFICACIONDE DAÑOS
Urgency Class
Description
1 Recuperación de
Se considera que la resistencia y/o estabilidad del dique
emergencia
representa un peligro inminente. Recuperación debe ser
llevada a cabo urgentemente (1-2 días)
2 Recuperación
Se considera que la resistencia y/o estabilidad del dique no
urgente
representa un peligro inminente. Recuperación debe ser
llevada a cabo con cierto grado de urgencia (1-2 meses)
3 Restaurar antes
Se considera que la resistencia y/o estabilidad del dique no
de la temporada
representa un peligro inminente y no tiene potencial de
invernal
empeorarse en un corto plazo. Recuperación debe ser llevada
a cabo antes del comienzo de la temporada invernal.
4 El estado del
Se considera que la resistencia y/o estabilidad del dique no no
dique no se
se encuentran comprometidas bajo normas de operación
encuentra en peligro
establecidas y no tiene potencial de empeorarse en un corto
inminente
plazo. Recuperación debe ser llevada a cabo en un plazo más
largo.
PASO 3: PREPARAR INFORMES DETALLADOS DE LA INSPECCIÓN
PASO 4: TOMAR FOTOS
PASO 5: PREPARAR UN CRONOGRAMA PARA LA RECUPERACIÓN
7
4.
DIAGNOSTICO
PROPOSITO
El objetivo del diagnóstico es reducir los datos de modo que pueda conocer el estado o condición
actual del carillón para poder determinar la urgencia de las medidas de recuperación y las acciones
de aseguramiento del cumplimiento de normas correctamente.
DEFINICIÓN
Para el diagnóstico, los valores observados o resultados de mediciones se comparan con los
umbrales predeterminados o niveles determinados que ameriten intervención (por ejemplo, altura,
volumen de material removido por hormigas, perfil de evaluación).
MÉTODO
Los siguientes métodos se deben implementar:
• Mapa base y reglamento
• Resultados de observaciones
• Guías técnicas de diseño y umbrales de intervención
CLASIFICACIÓN DE URGENCIA
Los cuadros 3.1y 3.2 determinan los niveles de modificación del dique y la clasificación de urgencia
de reparación. Un programa de reparación/restauración puede ser preparado con base en esta
clasificación.
8
5.
PLANEACION E IMPLEMENTACION
Los resultados de la inspección, incluyendo la planificación de las medidas de reparación necesarias,
se informan en este subproceso.
PROPÓSITO
El propósito de la fase de Planificación y Ejecuciónes definir, priorizar y realizar las acciones
necesarias a fin de que la modificación del carillón sea reparada.
PLANIFICACIÓN
En esta etapa las medidas requeridas son definidas, priorizadas e incorporadas en un programa. El
informe debe determinar los recursos que son necesarios para las medidas de recuperación del
dique.
IMPLEMENTACIÓN
Mantenimiento
Operaciones de emergencia.
La realización de las operaciones de emergencias lleva a cabo durante todo el año. El daño debe ser
restaurado inmediatamente después de descubrimiento;
Mantenimiento menor. Realizar reparaciones menores, todo el año. Las reparaciones de deben
realizar hasta un máximo de 3 meses después de la observación. Incluir control de las hormigas
simultáneamente con la realización de trabajos secundarios de mantenimiento.
Mantenimiento mayor. Se necesita establecer un programa multianual. La duración del programa
depende de los recursos disponibles y la urgencia de reparación.
Cumplimiento de las regulaciones
Urgente. Los asuntos que requieren atención urgente son inmediatamente transmitidos;
No es urgente. Observaciones que determinen condiciones que no son urgentes deben comunicarse
dentro de un plazo no mayor que seis meses
Invocación de entidades en deuda. Las entidades con atrasos en cumplimiento de sus compromisos
recibirán una carta con observaciones sobre la cartera de compromisos, las acciones requeridas y los
períodos de ejecución.
Refuerzo
Si un nivel mayor de estándar de seguridad es requerido entonces se debe proponer una acción de
mitigación.
En esta fase de un programa de recuperación debe ser preparados.
9
ANEXO 1 REGLAMENTO, MAPA BASE Y PLAN DE PROTECCION DE INUNDACIONES
Reglamento
La autoridad del agua (o del dique) trabajan con leyes y regulaciones. Por ley se les permite hacer
establecer ciertas reglas y regulaciones para apoyar las tareas asignadas.
Estas regulaciones salvaguardan la función del dique y protegen los diques de las actividades ilegales
tales como la excavación y la construcción en lugares no aptos. Por lo tanto, las autoridades protegen
las zonas adyacentes y deben reservar el espacio para obras futuras para refuerzo del dique.
Estas zonas protegidas se identifican como tales en el Mapa Base del dique. El mapa base es por lo
tanto importante para el ámbito de aseguramiento de cumplimiento de normas relacionadas al dique.
Mapa Base del dique
La Ley del Agua obliga a las autoridades a tener Mapa Base del dique
- La autoridad del agua es responsable de la generación de un Mapa Base, en el que se describe
cómo se debe comportar el dique y como son diseñados: localización, geometría, tamaño y
construcción.
- En este mapa también se establecen las entidades en deuda y las obligaciones de mantenimiento
- La ubicación del dique, las zonas adyacentes de protección y zonas reservadas para el futuro deben
indicarse en mapas de localización
Plan de protección de inundación
Este plan de control maneja las calamidades que puedan surgir en períodos de inundación.
El control adecuado tiene como base un modelo de escalada. Cada fase responde a los progresos de
la inundación y el estado de las estructuras de protección de inundación en conjunto con el avance
del despliegue de los cuerpos de emergencia.
Se distinguen las siguientes fases:
Fase 0 actividades anuales,
Fase 1 Mayor vigilancia (en particular, el cierre de estructuras que cruzan el dique),
Fase 2 Vigilancia del dique y reparación menor
Fase 3 Vigilancia permanente del diquey trabajos de reparación mayor para prevenir daños o
rompimiento del dique
Control de las defensas contra inundación por lo general se llevará a cabo mediante el despliegue de
personal y recursos de la autoridad del agua. En situaciones extremas, las autoridades del agua
inicialmente deberán trabajar con contratistas. Además, para acciones específicas con las organismos
de socorro, tanto a nivel local como regional, tales como el cuerpo de bomberos. En casos extremos,
el despliegue de unidades de emergencia nacionales podría ser necesario.
La colaboración con otras autoridades y contratistas debe ser planeada y simulada con mucha
antelación. Esta organización y el simulacro forman parte del plan de protección contra inundaciones.
10
ANEXO 2 INSTRUCCIONES DE TRABAJO
Este anexo contiene un ejemplo de trabajo.
PREPARACIÓN
Cada inspector debe tener:
1. Mapas
2. Lista de los carillones que indican abscisado y longitudes
3. Esta Observación de Instrucción
4. Planificación del trabajo concreto
5. Cámara
6. Indicador de escala
7. Computador de campo
8. GPS
9. Dotación de vestido adecuada
Cada inspector debe tener la siguiente información:
1. Vestimenta adecuada, identificación apropiada
2Nuevos desarrollos en la política, regulación
3 Manual de operaciones de computador y equipo GPS
REQUISITOS DE DESEMPEÑO
1
Implementación de las observaciones es realizada por lo menos por 2personas.
2
Que al menos una de las personas cumpla con los siguientes requisitos:
2.1
Educación mínima:
2.1.1 Educación secundaria a nivel técnico, orientada a ingeniería civil o ingeniería agrícola;
2.1.2 Ser calificado como inspector de diques, dos cursos (incluyendo la patrulla del dique);
2.1.3 Curso de actualización anual
2.1.4 Curso sobre cómo atender quejas
2.2
Nivel de experiencia: experiencia como interventor, evaluador de trabajos.
2.3
Área de conocimiento: Los encargados de la inspección deben tener conocimiento local de la
zona inspeccionada
2.4
No tener limitaciones físicas
2.5
Medios de transporte para acceder áreas remotas
3
La segunda persona debe tener las siguientes cualidades:
3.1
No tener limitaciones físicas
3.2
Ser calificado como inspector de diques, un curso
4
Las inspecciones se realizan a pie. El inspector va sobre la corona mientras el acompañante
camina a lo largo de la zona húmeda.
OBSERVACIÓN
Requisitos de los informes de observación
5
Fotografías deberán cumplir los siguientes requisitos:
5.1
Uso del indicador de la escala
5.2
Hacer una toma en la que toda la imagen comprenda el daño
5.3
Crear una visión global
5.4
Evaluar si son necesarias más fotografías
6
Observaciones de los daños para capturar imágenes en centímetros.
7
Una rareza no es necesariamente un tipo de daño. Cuando exista la duda, capturar la
imagen.
8
Cuando este lloviendo es lógico que se vean zonas húmedas en el campo. Registre la
localización y vuelva más tarde para ver si las zonas húmedas persisten después de un
período seco y registre las condiciones climáticas en el informe de inspección.
11
Empresa
Waterschap Aa en Maas
Royal HaskoningDHV
Dirección
Pettelaarpark 70, Den Bosch 5201 GA, Holanda; T +31.73.6156905
Laan 1914, No. 35, Amersfoort 3818 EX, Holanda T +31.88.3483383
12
Royal HaskoningDHV
ANNEX 8
Water governance and regional water authorities in the
Netherlands (partially derived from [14])
LW-AF20130064
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The regional water authorities are the oldest form of democratic government in the Netherlands. The first
regional water authorities date back to the 13th century, which is all to do with the geographic situation of
the country. More than half the country would be flooded but for the dunes and dams that protect human
beings, livestock and properties against storm floods coming from the sea and torrential rivers. Extreme
rain, too, can cause great inconvenience. The many dikes, locks, pumping stations, weirs, canals and
ditches keep the Netherlands habitable.
The regional water authorities are responsible for the water management on a regional and local level. The
concept of ‘water governance’ can be described as that part of public care that relates to flood protection,
the water regime (surface water and groundwater in both the quantitative and qualitative sense) and the
waterways. It focuses on the habitability and usability of the land and the protection and improvement of
the living environment. From this description it is also apparent that, in the execution of their tasks, the
regional water authorities fulfil the provisions of Article 21 of the Dutch Constitution: ‘Government care is
aimed at the habitability of the country and the protection and improvement of the environment.
The importance of good water governance is growing as a result of the rising sea level, climate change,
land subsidence and urbanisation. Six regional water authorities are also charged with road management.
Although strictly speaking this duty is not related to water management, it falls within the somewhat
broader concept of ‘Public Works and Water Management ’.
Water governance is realised by means of infrastructural works: water control works such as rivers, lakes,
canals, ditches, dikes, pumping stations, locks, weirs, culverts, bridges and sewerage treatment plants.
These works are crucial for keeping the Netherlands habitable. The regional water authorities draw up byelaws (Keur) to safeguard the correct maintenance and functioning of these structures. For example, it is
generally prohibited to carry out activities such as building, excavating or planting greenery, on, in, over or
under water control works without the permission of the regional water authority. The crucial importance of
these infrastructural works is also clear from the Dutch Criminal Code, which makes deliberately damaging
such works punishable.
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APPENDIX 9
Ownership of the Aguablanca dike
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Figure 17
Page 1 of the Act of Sales of Aguablanca
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Royal HaskoningDHV
Figure 18
Page 2 of the Act of Sales of Aguablanca
LW-AF20130064
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Royal HaskoningDHV
Figure 19
Rio Cauca
Page 13 of the Act of Sales of Aguablanca: CVC stays owner of the left bank of the
LW-AF20130064
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Royal HaskoningDHV
APPENDIX 10
Table of damage and investment costs
LW-AF20130064
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Royal HaskoningDHV
LW-AF20130064
appendix 10
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Aguablanca Dike along the Cauca River, Cali, Colombia

Transcription

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