Estimación de los sedimentos C. Lehmann

“Métodos para la estimación de
sedimentos”
Europakarte
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Densidad de la Populacion Suiza
• populacion densa
• Uso del suelo: conflicto entre la natura y la actividad humana
Hace pocos anos: elaboracion de mapas de riesgo
estimacion del arrastre de fondo=
una herramienta importante para la elaboracion de mapas de riesgo y la
planificacion del ordenamiento territorial tanto como para la planificacion y
construccion de medidas de proteccion
2 metodos para la estimation del aporte de sedimentos en cuencas alpinas
Como determinar
el aporte de los
sedimentos?
Estimación del Transporte de Sedimentos a través de
Depósitos
Estimation of sediment transport by sediment retention
reservoirs
…por una red de“medicion“…
Por la calculacion a travez de formulas…
?
Dos metodologias para
la estimacion ….
Metodologia
„Lehmann“
„Gertsch“
project
PH D Thesis 1993
PH D Thesis 2009
development
80 torrents, 1987-1992
58 events , 1987-2005
Estimated
Process
Sediment transport
Debris flows
Estimated bed
load
Bed load balances
Total Bed load charge
Bed load balances
Total Bed load charge
Return period
100 years
Return period
>100 years
Metodologia „Lehmann“
A Handbook with description of the method is available…
Erosion + Transport
Accumulation ?
Sediment yield? Scenarios?
Retention Basin planned
Preparations
Procedure to assess
sediment yield in
mountain streams
Collect data
Study and interpret data
First evaluation of mountain stream
Collection and processing of
discharge information
Field Work
Procedimiento de la
Estimación del Aporte
de Sedimentos en
Torrentes
Check results of prepartion work against
field conditions
Assign mountain stream to a category:
- no debris flow stream
- debris flow stream with deposits
- debris flow stream without deposits
Record parameters applicable to
category
Analysis
Calculation of sediment yield at the cone
for the corresponding category
Plausibility check and sensitivity
analysis
Assessment in the field…
Deslizamiento
Flujo de Lodo
Transporte en
Barranca
Fuente
de erosion?
Cual de los
procesos es
relevante ?
Falla
de la Escarpa
Transporte
en el Rió
Alta relevancia
Relevancia probable
Relevancia posible
Calculo con formula…
gross
Transportkapazität
Bannwald
klein
Pendiente…
?
?
Dimensiones?
Aporte lateral:
• Deslizamientos
espesor
?
longuitud
Ejemplos para la estimacion de los volumenes…
Propuestas para cada tipo de fuente
de sedimentos …
Assessment of sediment yield in
mountain streams
Estimación del Aporte de Sedimentos en Torrentes
Procedure:
Determination of sediment balance for each
channel section
Procedimiento:
Determinación de la Erosión y de la
Acumulación para cada sección del Torrente
Level of operation:
– Handbook
– Theory book
– Computer program for calculation
Herramientas para el Procedimiento:
– Manual
– Libro Especializado
– Programa de Computación
...por tramos...
Estimation of sediment transport in small mountain streams
Resultado de la Estimación del Transporte de
Sedimentos en el Torrente “Guppenruns”
Volume
Sediment transport during a 100-year flood in the Guppenruns
Transport capacity
Cross section Nr.
Sediment yield
Sediment potential
Deposits
Scenarios with a short and long rainfall input with
a river bed widening
Q = 57 m3/s
Q = 83 m3/s
25000
940
Sefinenlütschin
Sefinenlütschi
920
20000
900
change of bed level
Mdg. Trümmelbach
Trümmelbach
Mdg.
Bornige Brücke
Brücke
Bornige
Feststofffracht (m3)
880
15000
860
840
10000
820
Mattebach
Mattebach
untere
untere --- obere
obere
Stechelbergbrücke
Stechelbergbrücke
Lange Ganglinie
5000
800
780
760
0
Nr. der Querprofile
52
50
48
46a
45a
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
8956 / 2
8756
8556
8356
8156
7996
7856
7656
7456
7256
740
Metodologia „Gertsch“
Composition of data
Digital data, and field data
Delineation of channel parts and
adjoining slope parts
Possible with GIS
Extraction of input parameters
Scenario definition
qualitative, descriptive
Assessment of hillslope processes
Assessment of channel processes
Bed load balances in all channel parts in
dependance from scenario
Total bed load at fan apex
With the aid of developped
assessment matrixes for
hillslopes and channel
automated programme
Combined impact of all influence factors
Combined impact of all
influence factors is
essential for bed load
mobilisation
Every channel part is
influenced by a unique and
individual combination of
influence-factors
Combined impact =
complex
During the combined impact, the different influence-factors can:
cumulate each other
compete against each other

eleminate each other
I
Influence-factor do not have the same weight in each situation
Influence factors – system element-level
Understanding system element studying channel part
„local disposition“
Channel part to be assessed
perspective
Local disposition
Bed load supply
Edisriederbach, Sachseln
Leimbach, Frutigen
Milibach, Meiringen
rock
limited
unlimited
Local disposition
Channel gradient
Torrent de Saxé, Fully
steep erosion
Rio de Tennasses, Château-d‘Oex
flat deposition
Influence factors – interaction-level
Interaction between system elements
studying channel parts upstream
„conditions upstream“
Channel part to be assessed
perspective
Local disposition
Runoff supply / catchment area above
Les Creusats, Orsières
Influence factors – flip-over-level
flip-over-effects in the system
looking for critical constallations or processes
„negative factors“
special conditions or
processes
release of extreme debris
flows
extreme erosion rates
from release point untill
fan apex
flip-over-effect
erosion rates
> 30 m3/m
Channel part to be assessed
perspective
Release of debris flows in bastion-moraines
Rotlauibach, Guttannen (Foto: Flotron AG)
Confluence of several channels at the same location
Rotlauibach, Guttannen (Foto: Flotron AG)
Assessment criteria
Decision-making support
Assessment and quantification
Local disposition
Assessment line
Transport process
Quantification
Repressing and
increasing factors for
erosion
influence-factorcombination
4m3/m * 400m = 1‘600m3
40m3/m * 200m = 8‘000m3
0m3/m * 800m = 0m3
90m3/m * 130m = 11‘700m3
Total = 21‘000 m3
Simulacion
Evento 2004
(oleaje)
4m3/m * 400m = 1‘600m3
10m3/m * 200m = 2‘000m3
0m3/m * 800m = 0m3
17m3/m * 130m = 2‘210m3
Total = 6‘000 m3
Scenario
Flujo de
escombros
2m3/m * 400m = 800m3
2m3/m
* 200m = 400m3
0m3/m * 800m = 0m3
4m3/m * 130m = 520m3
Total = 1‘720 m3
Scenario
Bed load
transport
without release
of debris flow
Comparacion final
Methode Lehmann
Methode Gertsch
Estimated
Process
Sediment transport
Debris flows
Estimated bed
load
Bed load balances
Total Bed load charge
Bed load balances
Total Bed load charge
Return period
100 years
Return period
>100 years
3 days
2 days
Scale
< 50 km2
< 10 km2
Channel
gradient
> 2%
Return period
Necessary
time for
application for
a unit of
5km2catchment
> 10%
Gracias por su atencion!!!!!