An Alternative Solution to Erosion Problems at Punta Bete

Journal of Coastal Research
SI
71
75-85
Coconut Creek, Florida
2014
An Alternative Solution to Erosion Problems at Punta Bete-Punta
Maroma, Quintana Roo, Mexico: Conciliating Tourism and Nature
Itxaso Odériz†*, Edgar Mendoza†, Cristina Leo§, Gabriel Santoyo‡, Rodolfo Silva†, Rubí Martínez†,
Ernesto Grey††, and Raúl López††
†
Instituto de Ingeniería, Universidad Nacional
Autónoma de México, Mexico City, México
§
Huaribe-OHL Desarrollos
Playa del Carmen, México
‡
Ecoturismo Tres Rios
México
††
Tecnoceano
Cancún, México
www.cerf-jcr.org
ABSTRACT
Odériz, I.; Mendoza, E.; Leo, C.; Santoyo, G.; Silva, R.; Martínez, R.; Grey E., and López, R., 2014. An alternative
solution to erosion problems at Punta Bete-Punta Maroma, Quintana Roo, Mexico: Conciliating tourism and nature.
In: Silva, R., and Strusińska-Correia, A. (eds.), Coastal Erosion and Management along Developing Coasts: Selected
Cases. Journal of Coastal Research, Special Issue, No. 71, pp. 75–85. Coconut Creek (Florida), ISSN 0749-0208.
www.JCRonline.org
This paper presents an erosion problem found between Punta Bete and Punta Maroma, on the Riviera Maya, Mexico.
The case is worth studying as its features are quite complex: ecologically speaking, the area contains part of the
Mesoamerican barrier reef, the second largest in the world, an important area of seagrass and large mangrove fields;
on the other hand regarding economic aspects, the main activity is tourism, which is of vital importance to the region
and nationally. These two opposing interests need to be conciliated in the adoption of a solution to problem of
erosion on the coast as both are being degraded at the present. The chronic erosion reported in recent years is due to
natural causes, such as the slenderizing of the coral barriers and to anthropogenic causes such as local constructions
on the shoreline that interrupt the longitudinal sediment transport. This work describes the characterization of the
zone and analyses of marine climate and beach sediment. The hydrodynamics have been numerically modelled with
WAPO and COCO models and the morphological response of profiles with the XBeach model. Three possible
solutions are proposed and numerically tested, each of which present strengths and weakness. The three alternatives
are discussed in order to help decision making as some form of intervention is urgently required.
ADDITIONAL INDEX WORDS: Beach erosion, Riviera Maya, touristic developments.
INTRODUCTION
Beaches and dunes provide storm protection and damage
reduction against climatologic events, for both infrastructure and
natural systems beyond the beach, (Kobayashi et al., 2009). For
example, the damage found on the coast around Galveston,
Texas, was found to be less where the dune was higher (Doran
et al., 2009). This natural protection has also recreational,
biological and economic benefits. These are some of the many
reasons for preventing, or stopping, coastal erosion. This paper
presents the case of the erosion of the beach between Punta Bete
and Punta Maroma (henceforth referred to as PBPM). The area
is located on the Mexican Caribbean, forming part of the Riviera
Maya, in the state of Quintana Roo (Figure 1).
The study area hosts a wide variety of activities with different
characteristics as well as an ecologically invaluable
environment. It is also an important tourist destination, so there
are many conflicts between economic, social, ecological and
political interests that increase the complexity of any possible
solution to beach erosion. In the ecological part of the equation,
the area contains a section of the Mesoamerican barrier reef, the
second largest in the world and an important area of seagrass;
inland there are broad mangrove fields; all of which make up a
complex and delicate ecosystem. Economically, the zone has
great touristic potential, according to INEGI (Mexican National
Institute for Statistics and Geography) the touristic affluence in
Quintana Roo is the highest in Mexico and tourism contributes
____________________
DOI: 10.2112/SI71-009.1 received 12 February 2014; accepted in
revision 24 August 2014.
*Corresponding author: [email protected]
© Coastal Education & Research Foundation 2014
over 70% of the gross domestic product of the State of Quintana
Roo (Fay, 2013).
Figure 1. Location of the study area, Punta Bete-Punta Maroma.
PBPM is within Mexico´s most vulnerable areas to hurricanes;
47 of these storms have been registered here from 1948 to 2007
(Silva et al., 2012). Recently, the occurrence of hurricanes e.g.,
Gilbert in 1988 and Wilma in 2005 (www.nhc.noaa.gov/ for
more details), caused severe damage to infrastructure, economic
activities and social wellbeing.
In recent years the area has suffered severe beach erosion
which has increased the vulnerability of the infrastructure there.
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Odériz et al.
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As a consequence, the tourist industry may decline and, in
addition to the local economic repercussions, the attractive,
positive image of Quitana Roo´s beaches could affect tourism at
national level. Any erosion in PBPM is considered to have a
negative effect, so adequate coastal management is required and
for this the features of the area need to be characterized in order
to find a solution which can conciliate the social and economic
interests with the environmental elements that made this site so
important a touristic destination. This work, then, focuses on the
characterization of the study area as the means to acquiring
sensibility in order to propose alternative solutions within the
aforementioned constraints, numerically test them, choose the
optimal
solution
and
issue
coastal
management
recommendations at PMPB.
CHARACTERIZATION OF THE STUDY AREA
Littoral Cell: Land and Marine Environments
The littoral cell is physically delimited by the Bete (PM) and
Maroma (PM) tips, which are two natural headlands, Figure 1.
Similar to many other littoral cells in the Mexican Caribbean,
the PMPB coastal area is largely covered by vegetation (mainly
mangrove) as can be seen in Figure 1. The area is located over
an aquifer which discharges fresh water to the sea. There are few
surface rivers in the area, but close to the central point between
the two headlands there are three small (Figure 2).
The marine zone can be divided in two areas: a) the bay, and
b) the reef, as can be seen in Figure 2. Within these, ten types of
environments can be distinguished: a shallow sandy area,
seagrass, a landward coral reef, a seaward coral reef, a seaward
transition zone, a sand channel, patches of Gorgonacea, a deep
sandy area, a pronounced cliff and the continental shelf.
In the reef section the reef crest is well defined and is
approximately 4 km long, varying in distance from the shore
from 250 to 800 m. Up to a point, it is the existence of the reef
which is responsible for the formation of PM. In the 1990s a
reduction in the coral reef mass was documented (De’ath et al.,
2012; Gadner et al., 2003; Hughes et al., 2003). This was due to
disease, blanking and the growth of epibiont organisms (Lessios
et al., 2001; Toller, 2001) As a result PM receeded. This
observation coincides with the knowledge we have, that the crest
height of a reef controls the amount of wave energy dissipation
and that the distance between the reef-crest and the shore
determines the vulnerability of the beach to morphological
changes, (Ruiz de Alegria-Arzaburu et al., 2013). In this same
study they found that a reef-crest degradation of 1 m can result
in an increase in incoming wave energy of up to 10%.
The bay section is the southern part of the study area and has
shallow sandy areas with some small patches of seagrass. It is
characterized by the absence of a coral reef, as coral is unable to
grow here because of the superficial and subterranean fresh
water discharges (Bacabes del Mar, 2013). At the southern limit
of the study zone, PB, an incipient patch of coral reef can be
found due to the absence of fresh water discharge spots. This
reef gives shelter to the southern part of the study area and is,
probably, responsible for the existence of Punta Bete.
Geological evidence of the effect of the coral reef in the stability
and regression of PM are the beach ridges found there that can
be seen in the left panel of Figure 2.
Figure 2. Marine elements and environment at PMPB.
Present Sedimentology Characteristics
The small bay formed between the two headlands shows
almost no sediment interchange with neighbouring beaches,
which lets us classify the bay as a closed littoral cell. The sand
from the beach face is moved offshore in the form of cross-shore
transport during storms; most of this material is usually
deposited in the shallower part of the study area, but if the storm
is intense enough, the sediment is carried offshore from near the
cliff. In both cases, once the sand has been taken away from
beach, it is almost impossible that it get back, as the mean wave
climate is of quite low energy.
Figure 3. Location and definition of the sand profile samples,
coordinates UTM 16N.
At the North, the beach is defined by mangrove, rocky and
sandy areas and at the South the beach is sandy. The sediment of
both areas is mainly of biogenic origin, formed by oolite,
calcareous shells, and coralline fragments, (Carranza et al.,
1996). These sources generate new sediment at very low rates,
so the system has sediment deficit and thus the resilience of the
beach is very low. To get an idea of the stability of the beach,
seven sand profile samples (drying beach, swash zone and surf
zone) were taken along the study area in the locations shown in
Figure 3.
Journal of Coastal Research, Special Issue No. 71, 2014
An Alternative Solution To Erosion Problems At Punta Bete-Punta Maroma, Quintana Roo, Mexico
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To get an idea of the stability of the beach, seven sand profile
samples (drying beach, swash zone and surf zone) were taken
along the study area in the locations shown in Figure 3.
Table 1 summarizes the main parameters of the sand samples,
i.e. d50, fine material portion (%f), roundness (R), sphericity
(Sp), shape factor (Sh) and fall velocity (w). The mean measured
density of all the samples was 2.2 g/cm3. In Table 1 shows the
parameters of the samples: D stands for drying beach, Sw is
swash zone and Su is surf zone.
Table 1. Sediment relevant parameters.
Site
MK
TR2
TR1
K2
KN
KV
PM
Sample
D
Sw
Su
D
Sw
Su
D
Sw
Su
D
Sw
Su
Sw
Sw
D
Sw
Su
d50
(mm)
0.4
0.2
0.2
0.4
0.4
0.4
0.4
0.6
0.8
0.3
0.2
0.1
0.3
0.2
0.3
0.3
0.2
%f
R
0.33
0.42
1.73
0.14
0.42
3.59
0.16
0.42
0.85
0.53
1.21
4.52
0.08
0.39
0.31
0.24
2.25
0.87
0.87
0.86
0.88
0.87
0.78
0.88
0.86
0.87
0.88
0.88
0.87
0.88
0.86
0.88
0.88
0.86
Sp
Sh
0.82
0.83
0.82
0.84
0.81
0.86
0.84
0.82
0.82
0.85
0.87
0.87
0.86
0.82
0.85
0.85
0.82
0.6
0.7
0.7
0.7
0.6
0.6
0.7
0.6
0.6
0.7
0.7
0.7
0.7
0.6
0.7
0.7
0.6
w
(m/s)
0.04
0.01
0.01
0.03
0.04
0.03
0.03
0.05
0.07
0.02
0.02
0.01
0.03
0.02
0.03
0.03
0.02
Figure 4. Recent infrastructure constructed along the PMPB beach.
Although a full topographic survey was not available, ten
dune profiles from the southern part of the study area (Figure 4)
were provided by Consultores en Gestión, Política y
Planificación Ambiental. These profiles were recorded between
April and May 2013 and are shown in Figure 5.
The results of the sediment analysis show that at points K2
and MK the grain size is larger in the drying beach, which
indicates profile instability and that the sand is being lost from
these areas. The largest sediment sizes all along the study area
were found in section TR1, probably because it is close to the
river discharges and some terrigenous sediments can get there.
This section, according to the grain size distribution along the
profile seems to be reasonably stable. In all the other sample
sections it was found that the grain size distribution along the
beach profile decreases away from the shoreline, which
indicates that these profiles are more stable than those at K2 and
MK.
Shoreline and Dune Profiles
Unfortunately there is almost no historical data available for
the study area; only some satellite imagery and the records of
human actions in the last decade. A summary of the
perturbations which took place in recent years is presented in
Figure 4. The construction of groins and breakwaters and the
placing of geotextile bags is visible in several sections of the
coast; most of these structures were installed using touristic and
recreational philosophy; disregarding the physical processes
involved. In Figure 4 it can also be seen that the main
consequence of the infrastructure selected is the interruption of
the longshore sediment transport. This mechanism is highly
undesirable as the natural capacity of the beach to distribute the
sand and keep a sound state disappears.
Figure 5. Dune profiles from the south of the study area.
The beach in the areas located through the profiles P1, P2 and
P10 has been preserved and native vegetation up to where the
mangrove begins can still be found. However, the rest of the
profiles were modified by the construction of a golf course and
other infrastructure (P3, P5, P6, P7, P8 and P9) and only the
foredune is still in a sound state. Profile P4 is in a relatively
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good state of conservation, as only the top of the dune has been
flattened.
The evolution of the shoreline in recent years (2006 to 2010)
was assessed by comparing satellite photographs, Figure 6
shows detailed images for 3 zones. In A, PM, the erosion is
evident, as mentioned earlier this is mainly due to the reduction
of coral reef protection. The shoreline retreated here almost 10
m. The shoreline in the central section, B, has remained more or
less in the same position, with only a small variation; some parts
show erosion, others show accretion. Section C, PB is by far the
most damaged as it has suffered from the naturally driven
erosion (including the effects of Hurricane Dean in 2007) and
also the effect of the badly planned infrastructure that blocks the
longshore sediment transport. From 2006 to 2010 an average of
29 m of beach was lost.
The methodology used, in order to define a feasible solution,
comprised: the characterization of local hydrodynamics, the
numerical modelling of wave and current fields and the
numerical modelling of the beach response to storms (using
available beach profiles) followed by the numerical testing of
three possible alternative solutions and the selection of that with
the best performance.
Marine Climate
Wave and wind data from 1948 to 2010 were taken from the
Atlas of Wave Climate by Silva et al., (2007). This data are the
result of a reanalysis based on the hybrid wave model WAMHURAC, WAMDI-Group (1988) and Silva et al., (2002).
Annual and seasonal statistical data were used to define the
mean and extreme regimes; the results are shown in Figure 7.
Figure 7. Mean period-significant wave height joint probability (a) and
wave height and direction rose (b).
Figure 6. Shoreline evolution, 2006-2010.
After the analysis of the sediments, shoreline evolution and
the available profiles, it can be said that the present dynamics of
the PMPB beach system are of low resilience as the beach and
dune elements have been degraded by both natural and
anthropogenic actions. In addition, as the headlands that govern
the morphology are retreating, the shoreline in between is also
eroding, a process worsened by the infrastructure that interrupts
the longshore sediment transport. Therefore, taking into account
that the tourism industry here is very important for the local and
national economy, some form of engineering solution must be
found. The main goals of any conservation action should be: to
ensure the continuity of tourist activities, to offer security to
visitors, to recover the resilience of the system and to preserve
the valuable environmental elements described earlier.
In Figure 7 it can be seen that the dominant waves comes
from East and SE directions with significant wave height (Hs)
lower than 1.5 m and a mean period (Tm) of 4-6 s. In winter, due
to cold fronts, extreme events with directions NNE, NE and
NEE, with Hs of 2-3 m and Tm of 6-8 s, occur frequently. In
summer there are sporadic extreme events with higher energy:
Hs of 4-13 m and Tm of 6-12 s with dominant incoming
directions from E and ESE.
Hurricanes have a strong negative impact on the stability of
the beach, causing severe erosion. Three hurricanes had
substantial effects: Gilbert in 1988 with a minimum central
pressure of 925 mb and maximum sustained winds of 130 km/h
when it was close to PBPM; Wilma, 2005, passed close to the
zone with a central pressure of 930 mb and wind velocities of
120 km/h, in 2007 Dean was a weaker storm: 960 mb central
pressure and 75 km/h wind velocity (www.noaa.gov).
Regarding wind climate, the dominant directions are E and
NEE, with a medium velocity of 5 m/s. In winter, the main
directions are ENE and E with velocities of 10 m/s due to cold
fronts. The highest wind velocities occur in summer, reaching
50 m/s.
Astronomic tide time series recorded at Puerto Morelos,
approximately 17 km north from the study area (see Figure 1)
were taken as valid for the study area; the tide regime in PBPM
is microtidal and semidiurnal with a mean range of 20 cm.
The storm surge was obtained from synthetic data computed
by Duran (2010) with the numerical model MATO (Posada et
al., 2007), which solves the 2D Non Linear Shallow Water
Journal of Coastal Research, Special Issue No. 71, 2014
An Alternative Solution To Erosion Problems At Punta Bete-Punta Maroma, Quintana Roo, Mexico
79
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Equations (NLSWE). The estimated sea levels at the shoreline
as a function of wind direction and velocity are shown in Figure
8.
Figure 8. Sea levels at PMPB as a function of wind direction and
velocity.
Modelling of Wave Propagation and Currents
To represent the hydrodynamic conditions in the study area
two models were used: WAPO, Silva et al., (2005), a numerical
wave propagation model based on the Modified Mild Slope
Equation; and COCO, Mendoza et al., (2007), which computes
wave induced currents solving the NLSWE. A total of 80
combinations of significant wave heights (1, 2 and 4 m), mean
wave periods (7, 8, 10 and 12 s), wave directions (NEE, E, ESE
and SE) and meteorological tides (0, 1 and 2 m) were modelled.
With all these conditions, mean regime, mild storm, severe
storm and hurricane scenarios were covered.
cell, and another with high resolution (6 × 6 m), that only
covered the southern part of the domain. This division was made
as the southern area is exposed to larger waves (very few reefs
exist here), so this is the area with worst erosion. Figure 9 shows
an example of the results obtained with WAPO on the low
resolution grid for Hs=2 m, T=8 s, incident direction NEE and
meteorological tide of 2m. It can be seen, as was mentioned
before, that the southern shoreline receives higher waves, up to
2.5 m high, while the area around PM is naturally protected by
the reef barrier. This scenario corresponds to severe storm
conditions but the general pattern is similar in all the modelled
scenarios. These results are in agreement with previous works
regarding the role of the coral reef as a natural defense (i.e.
Alvarez-Filip, 2011; Gourlay and Colleter, 2005; Hearn, 1999;
Lowe et al., 2005).
Figure 10 shows an example of the results of wave
propagation and wave induced currents on the high resolution
grid for Hs=2 m, T=7 s, incident direction NEE and null
meteorological tide which correspond to a mild storm; again the
southern part receives waves of around 2.5 m and the wave
induced currents reveal a pattern close to PB that clearly explain
why the sediments are being lost to the south.
Figure 10. Propagation of waves (a) and currents pattern (b) with high
resolution mesh for Hs=2 m; Tp=7 s, dir=NEE, tide=0 m.
Figure 9. Propagation of waves, mesh with low resolution for H=2 m;
T=8 s, dir=NEE, tide=2 m.
The hydrodynamics were estimated in two separate grids, one
of low resolution (15 × 15 m), which covered the whole littoral
Response of the Beach Profile
The numerical model used to analyze the beach profile
behavior under storm conditions was X-Beach, Roelvink et al.,
(2009). The only topographic data available was the modelled
profiles presented in Figure 5. The main focus of this numerical
exercise was to assess the outcome of the “do nothing” solution
as well as verify the vulnerability of the actual state of the dunebeach system to mild (T1 and T2) and severe (T3, T4 and T5)
storms and hurricanes (T6 and T7). Table 2 summarizes the
Journal of Coastal Research, Special Issue No. 71, 2014
Odériz et al.
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modelled scenarios, where Mt stands for meteorological tide and
t for simulation time.
Table 2. Hydrodynamic parameters used in modeling Xbeach.
Storm
T1
T2
T3
T4
T5
T6
T7
Hs (m)
2
2
2
2
4
4
4
Tp (s)
8
8
8
8
10
10
10
Dir
ESE/E
ENE
ESEE
ESE/E
ENE
ESEE
Mt (m)
0
0.8
1.3
1.6
0.8
1.3
1.6
t (h)
7
7
7
7
3
3
3
Figure 11 shows the results of X-Beach modeling, in which it
can be seen that the profiles with a sound dune (profiles 1, 2, 4
and 10) can endure mild and severe storms with less damage and
having the possibility of a natural recovery. In contrast, the
profiles with the most damaged dunes are rapidly eroded. An
important feature revealed by these results is that an important
part of the sand taken by the storms is deposited in the nearshore
area and only a small part is lost offshore; this means that it is
available for artificial nourishment.
Figure 11. Response of the profiles to storms.
As a result of the characterization of the study area, the main
problems detected in the study area are
(1) Only a few of the original coastal dunes are conserved and
in a sound state, which means that resilience is decreasing as
the sand supply to the beaches during storms is limited or
stopped.
(2) Disregarding the causes, the reduction of the reef
dimensions is increasing the wave energy that arrives
onshore and thus the coastline is moving landward, looking
for a new stable state.
(3) The combination of density, sphericity and shape factor of
the sediment results in easily transported sand; this, and the
lack of sediment sources, means that the littoral cell has a
sediment deficit.
(4) The numerical results and the satellite imagery show the
process of permanent erosion in the system.
(5) Several structures, aligned perpendicular to the coast, i.e.,
groins, have been constructed along the beach interrupting
the longshore sediment transport and thus worsening the
sediment deficit in some areas.
(6) The stability of the beaches is often threatened by storms
and hurricanes.
All the above factors lead us to describe the PBPM system as
having low vulnerability, in a state of permanent erosion with a
low possibility of auto-regeneration and in urgent need of
intervention in order to preserve the natural value of the area and
its social and economic interests.
SHORELINE PROTECTION ALTERNATIVES
The solutions suggested assume that regenerating and
protecting the beach in certain segments can be the means to
recovering the protection function of the dune-beach system in
the entire littoral cell and thus preserving its attractiveness and,
hence, its economic viability. It is desirable that the solution be a
combination of rigid structures, intended to control wave energy,
and soft actions (i.e. artificial nourishment), to control sediment
transport. Submerged structures were chosen as the rigid
elements as they have low visual impact, produce stilted wave
breaking and reduce wave transmission, which helps water
renewal in the protected area
Three alternatives were proposed and numerically tested. For
each alternative the same 80 wave conditions used in the
characterization were modelled and the profile response was
evaluated with X-beach model in the ten profiles shown in
Figure 5. The description of each alternative and the numerical
findings are presented below. It is important to remark here that
all the alternatives include beach nourishment using sand taken
from the nearshore area of the system.
Alternative A has four medium to large submerged structures
placed in critical positions, to recover the protective function of
the reef barriers. A sketch of the proposed location of the
structures is shown in Figure 12. All the barriers are crested at
the mean sea level.
Structures A1 and A2 of alternative A are intended to extend
the length of the existing reef barriers, thus reducing the wave
energy that reaches the shoreline. At the same time these
structures may help to retain part of the sediment that travels
offshore and cannot return the beach. In turn, structures A3 and
A4 are also wave control structures which would reduce the
wave energy that is reaching PM as a result of the reef
slenderizing so that the new stable position of the coastline can
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An Alternative Solution To Erosion Problems At Punta Bete-Punta Maroma, Quintana Roo, Mexico
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be found as soon as possible thereby reducing the dry sand loss.
The UTM coordinates of the tips of the structures, their lengths
and crest heights are shown in Table 3.
behind each barrier. This array of structures will not
immediately benefit the whole littoral cell; only the most
damaged sections. Anyway, the distribution of the sand from the
nourishment will strengthen the beach in the long term as long
as no severe storm or hurricane event occurs. The coordinates of
the tips of the structures and their main dimensions are shown in
Table 4.
Figure 12. Location of the submerged structures in alternative A.
Table 3. Location and dimensions of the structures in alternative A
Structure
A1
A2
A3
A4
East (m)
498240
498916
500571
501279
504486
504651
504932
505145
North (m)
2286320
2286980
2288831
2289586
2292678
2293080
2293664
2294198
Length (m)
945
1035
Figure 13. Location of the submerged structures in alternative B.
Table 4. Location and dimensions of the structures in alternative B
435
Structure
B1
575
B2
The numerical results for mean conditions show that the
structures have little effect on wave propagation and wave
induced currents, but as the wave conditions become more
energetic (mild storm, severe storm and hurricane) the structures
stop high waves reaching the coast. Some currents are found in
the protected area, which help to distribute the material from the
nourishment all along the littoral cell.
In alternative B the existing structures placed to protect PM
are eliminated, believing that the position and shape of the
headland can be left to reach its stable state freely, while the
protection and artificial stabilization can be focused in the more
damaged sections of the cell. The reduced cost of this alternative
is an additional reason for adopting this alternative. As can be
seen in Figure 13, where the location of the structures is shown,
structure B1 is similar to structure A1 in location, dimensions
and performance. On the other hand, structures B2 to B5 are
small submerged barriers intended to control wave energy but
also help to control sediment transport.
The numerical results of this alternative predict a local effect
of structures B2 to B5 and the possible formation semi-tombolos
B3
B4
B5
East (m)
498916
498191
498091
498054
498208
498160
499175
499238
499 920
North (m)
2286980
2286440
2287433
2287267
2287767
2287588
2289239
2289316
2289598
Lenght (m)
900
170
185
100
170
Alternative C has two groups of small submerged structures
as shown in Figure 14. In this alternative the idea of replicating
the function of the reefs has been abandoned for the sake of
reducing overall costs. The effects of barriers C1 to C9 in
controlling wave energy are purely local and their efficiency is
higher for the mean regime and mild storms than for more
energetic situations. On the contrary, they are better working as
sediment traps when intense storms occur. Figure 15 shows an
example of the wave propagation and the numerically produced
wave induced current fields.
The protected area offered by alternative C is smaller than in
the other options, as is its impact across the whole littoral cell.
However, this alternative has the advantage that it can be
constructed in less time and with smaller equipment.
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Odériz et al.
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The response of the beach profiles to the small barriers of
alternative C was estimated with the X-Beach model for all the
scenarios presented in Table 2. Figure 16 shows the results only
for those profiles in front of which a barrier was placed, i.e.
profiles P2, P3 P5 P7 and P8 of Figure 5. The numerical results
show that in general with barriers placed, the erosion caused by
the storms is less than without them. In agreement with the wave
propagation results, the submerged structures lose protection
efficiency as the intensity of the storm increases and, comparing
the results in Figure 16 with those presented in Figure 5, for
severe storms and hurricanes, the erosion is similar with and
without the barriers. A great difference in the performance of
alternative C is regarding sediment transport, that is, as the
structures are closer to the shore, the possibility of semi-tombolo
formation is greater. This means that the longshore sediment
transport will be impeded and may be blocked, so the artificial
nourishment may not distribute sediment along the entire
shoreline, nevertheless it will stay in the most damaged areas
and will not easily be removed.
Table 5. Location and dimensions of the structures in alternative C
Figure 14. Location of the submerged structures in alternative C.
Structure
C1
C2
C3
C4
C5
C6
C7
C8
C9
Figure 15. Wave propagation (a) and wave induced currents (b),
with alternative C barriers for Hs=2 m; Tp=8 s, dir=NEE, tide=0 m.
On the other hand, the maintenance costs needed to keep the
barriers and the artificial nourishment working properly may be
important in the event of a severe storm, perhaps even equaling
the original investment in the case of a strong hurricane. This
alternative seems to be most environmental friendly as it will not
require any construction in the marine area nor close to the coral
reefs.
East (m)
497933
497925
497948
497940
498004
497970
498096
498033
498215
498152
499175
499238
499397
499496
499920
500042
500216
500295
North (m)
2286445
2286245
2286823
2286623
2287196
2286999
2287562
2287372
2287921
2287731
2289239
2289316
2289427
2289439
2289598
2289684
2289876
2289967
Length (m)
200
200
200
200
200
100
100
150
120
The retreat of the shoreline is less in profiles 2 and 8 with the
structures of option C; on the other hand in profiles 5, 3 and 7
there are variations depending on the hydrodynamic conditions.
With respect to the dune height, in profiles P3, P5 and P8 the
effect of structure is not evident due to the wall at the edge of
the grid, and in profile P2 (storm 1, storm 2), P3 (storm 2) and
P7 (storms 4 and 6) the height is greater with the structure.
There is a reduction in the percentage of area eroded. The
shoreline retreat is very evident in P2 (storms 4, 5, 6 and 7) and
P8 (storms 2, 3 y 4). Modelling shows that structures work, but
dune regeneration would be recommendable to obtain a resilient
profile and provide more protection for hydrodynamic
conditions with longer return periods.
Regardless the solution selected, as said before, artificial
nourishment is recommended as well as the rigid barriers
(preferably after constructing the barriers). To select the
appropriate sand bank for this nourishment several factors were
considered (CEM, 2006):
Journal of Coastal Research, Special Issue No. 71, 2014
An Alternative Solution To Erosion Problems At Punta Bete-Punta Maroma, Quintana Roo, Mexico
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Grain-size distribution: The mean diameter, d50, of the fill
sand should be larger than the original sand in order to ensure
beach stability and reduce overfill. The optimum overfill ratio is
1.00 to 1.05.
Figure 16. Propagation of waves (a) and current patterns (b) with high
resolution mesh for H=2 m; T=7 s, dir=NE-E, tide=0 m.
Particle shape: The sphericity is better higher as this has
greater fall velocities, higher roundness enhances beach stability
and angular grains are more difficult to be suspended.
Colour: As important touristic activities are developed in the
area, the colour is important for the visual impact of the finished
project.
The sand found within the littoral cell in the nearshore area
has the following characteristics: d50 of 0.542 mm, 1.5% of fine
material, roundness of 0.867, sphericity of 0.785 and a shape
factor of 0.656; which considering the above mentioned
recommendations, can be used for the artificial nourishment
suggested.
DISCUSSION AND CONCLUSIONS
Conciliating the natural features and ecological services of the
coastal area with medium or high density touristic infrastructure
is difficult, and often seen as impossible. This is not the case in
places like the coast of Quintana Roo, where it is precisely the
natural richness of the area which has attracted touristic
development. What was not properly considered during the
planning and construction of the infrastructure is that Caribbean
coasts are highly vulnerable because of their sand characteristics
and availability, and that the intensity and energy of
hydrodynamic conditions here causes them to be very
destructive. As a result, there are many tourist developments
which have fallen into a vicious circle in which the
infrastructure degrades the natural elements (vegetation, dunes
and beaches) leaving the infrastructure itself without natural
protection, then the extreme meteorological events damage the
infrastructure; as a response, more poorly planned infrastructure
is constructed (e.g., groins and other barriers perpendicular to
the shoreline) which again degrades the natural elements. This
process occurs within the frame of larger natural cycles:
atmospheric (el niño, la niña), marine (sea level rise) and
ecological (reef slenderizing); which put the littoral systems in
critical and chronic situations.
Now, political, economic and social aspects make the “do
nothing” or the “remove all” scenarios unviable, so a wellplanned engineering project must be carried out in order to let
all those involved continue to prosper.
The present paper suggests a solution combining rigid and
soft measures as the means to recover the stability of all the
elements in the littoral cell Punta Bete-Punta Maroma. The soft
measure consists of artificial nourishment with sand taken from
the nearshore area. This sand, as has been numerically
demonstrated, was taken from the dry beach and placed
underwater by storms so, from this point of view, the soft
measure suggested can be viewed as a recovery of the original
state of the beach-dune system. It is straight forward to think
that this action alone may have a short life as the recurrent
storms that occur in the Caribbean will take the sand back to the
nearshore area. This is the main motivation for the addition of
the rigid part of the proposed solution.
Three alternatives for the rigid barriers were considered.
Alternative A aims to reproduce the original condition of the
littoral cell, in which the wave energy was controlled by the
coral reefs, in order to stabilize the PB and PM headlands. Given
that the position of the headlands determines the position of the
shoreline of the whole littoral cell, a stable state can be reached
Journal of Coastal Research, Special Issue No. 71, 2014
84
Odériz et al.
_________________________________________________________________________________________________
in mid to long term (in the short term the stability will depend
only on the soft measure). The construction of the large
structures in this alternative will prevent the sediment going
offshore but not to being transported underwater by mild storms.
Alternative A presents greatest efficiency in controlling the
wave energy of severe storms and hurricanes; this, the length of
the barriers and the depth in which they will be placed (5-7 m),
make this the most expensive option.
Alternative B combines the reproduction of the reef action
with local protection for the most damaged beach sections. The
barriers suggested in this alternative will only stabilize the
headland at PB, and a group of small structures will control the
waves and work as sediment transport traps. The effects of this
alternative will not affect the whole littoral cell; mainly the
southern and central parts. The small barriers, as they are placed
close to the shore, will stop the sediment in the beach being
deposited underwater by storms. Alternative B was the most
efficient for mild and severe storms.
Alternative C focuses only on protecting the beach sections
with worst erosion problems. This alternative has 9 short
barriers, placed very close to the shore (2 m depth). The main
objective of these structures is to dissipate wave energy and to
produce protected areas where sand settlement is favoured and
semi-tombolos are formed. This works well with the artificial
nourishment as the barriers stop the sand moving to the
nearshore, although longshore sediment transport is limited,
meaning that the benefits will be local and not affect all of the
littoral cell. This alternative shows better efficiency for a mean
regime and mild storms and it is possible that the barriers and
the soft measure may need maintenance and/or reconstruction
after a strong hurricane. The costs of this maintenance are not
high and the low initial investment of this alterative is cheaper
than A or B.
It is clear that there is no one, unique, solution and that the
economic aspect is not the only one to be taken into account in
making the decision. Instead, a coastal management plan is
needed to determine which dune-beach performance and which
of the engineering measures are desirable and compatible with
future development and tourism.
ACKNOWLEDGMENTS
This publication is one of the results of the Latin American
Regional Network global collaborative project ‘‘EXCEED –
Excellence Center for Development Cooperation – Sustainable
Water Management in Developing Countries’’ consisting of 35
universities and research centres from 18 countries on 4
continents. The authors would like to acknowledge the support
of the German Academic Exchange Service DAAD, the Centro
de Tecnologia e Geociências da Universidade Federal de
Pernambuco, the Fundação de Amparo a Ciência e Tecnologia
do Estado de Pernambuco-FACEPE and the Instituto de
Ingeniería of the Universidad Nacional Autónoma de México for
their participation in this EXCEED project.
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