Coastal Engineering
INTRODUCTION &
GENERAL STRATEGIES
Jos A. Jimnez
jose.jimenez@upc.edu
Laboratori dEnginyeria Martima
ETSECCPB
Universitat Politcnica de Catalunya
Barcelona, Spain
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Not only actuations in the coast
affect its stability.
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Ebro river
drainage basin
surface: 85,362 Km2
dam /reservoirs > 180
regulated basin 82,300 km2 (96.4 %)
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Coastal Protection Works
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Highly dynamic environment, most
of the natural driving terms (waves,
wind, surges, etc.) & induced
processes are random.
In many cases the dynamics is very
complex and hardly to be
accurately predicted.
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Processes vs Problems
Process
Physical coastal response (morphodynamics) to acting
driving terms (littoral dynamics) without adding any value to
the quantification of the response, e.g. area subjected to an
erosion of x m/y .
Problem
When a given coastal process has consequences and/or
implications on existing uses and/or resources, i.e. coastal
functions area affected.
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Elements in coastal actuations design:
To make use of an incomplete knowledge, guided by own
criteria and experience to estimate the most probable field of
actions / driving terms required for the problem solution.
To decide a risk level, taking into account socio-economic
and environmental factors and evaluating damages and
losses due to the failure of the work.
To forecast coastal modifications and impacts induced in the
area of influence (near and far fields).
To design correction / mitigation measures.
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Main targets of coastal protection works:
Coastal erosion
Inundation
Coastal Environmental restoration
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Problems associated to beach erosion
Shoreline retreat results in a beach width
insufficient to support actual (targeted)
coastal functions.
Different strategies and solutions exist
depending on the main acting process and
function of interest-.
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General
alternatives to
approach to erosioninduced problems
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General
alternatives to
approach to erosioninduced problems
Protection-rigidization
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Erosion, retreat and loss
perfil inicial
perfil inicial
ancho de
playa
ancho de
playa
muro
c
ancho de
playa
perfil erosionado
perfil erosionado
prdida
de playa
muro
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0
5
1957/73
10
15
El Fangar
spit
25
30
1990/00
35
40
El Fangar
bay
45
La Marquesa
4 km
2000/04
1973/90
control profiles
20
50
55
60
-20
-16 -12
-8
-4
0
rate of displacement (m/yr)
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General
alternatives to
approach to erosioninduced problems
Protection-reduction
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PROTECTION-REDUCTION
Objective: To reduce sediment transport rates along
the beach / to reduce the intensity of responsible coastal
dynamics/processes.
Effect: Beach maintenance.
Works / actuations: groins, breakwaters, etc.
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General
alternatives to
approach to erosioninduced problems
Nourishment
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BEACH NOURISHMENT: REPLENISHMENT vs
CREATION
REPLENISHMENT
Objective: Sediment supply to a beach where the
sediment (i) is being removed or (ii) has disappeared.
Effect: Beach maintenance or recovery.
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The resulting beach will behave as
before works.
Acting on problem effects and not
on the origins.
Sediment is supplied to
compensate losses.
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Ephemeral solution the work will disappear
Life period limited (dependent on design parameters)
If this strategy is adopted works have to be permanently
maintained
High maintenance costs (sustainable?)
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If needed (and feasible) includes additional works (structures).
Most of the sediment obtained from marine deposits.
Main problem
sediment availability,
social and environmental aspects,
need to re-nourish.
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SEDIMENT
Ideally (user) same than the native one or very similar
Ideally (work/engineering) coarser than the native one
Ideally (natural) that inducing the smallest impact on both
extraction and nourishment areas
FROM WHERE?
Sediment from the sea (dredging).
Sediment from deposits in land.
Sediment artificially produced (crushing).
Other sediment (e.g. glass).
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General
alternatives to
approach to erosioninduced problems
Retreat
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Brighton Beach Hotel, Long Island, NY (Scientific Am. 1888)
Special retreat (relocation)
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Cape Hatteras lighthouse
1999
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Managed
realignment
Tidal flow through
breaches in dikes in
Paull Holme Strays
(Humber estuary, UK)
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2100
2000
1900
1800
5m
10 m
4m
1700
distancia (m)
8m
1600
1500
5m
1400
4m
1300
1200
1100
1000
900
0
100
200
300
400
500
600
700
800
900
1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
distancia (m)
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