Environmental Design Guidelines for Low Crested Coastal Structures
by Hans F. Burcharth
Stephen J. Hawkins
Barbara Zanuttigh
Alberto Lamberti
Pages: 419
Publisher:
Edition: 1st, December 4, 2007
Language: English
ASIN: B0086QJXT4
Description
The effect of human activities is primarily local but can extend far away from the location of
intervention. This underlines the importance of establishing coastal zone management plans covering
large stretches of coastlines.
The interaction of wave climate, beach erosion, beach defence, habitat changes and beach value,
which clearly exists based on EC research experiences and particularly on results obtained by DELOS
Project (www.delos.unibo.it) for Low Crested Structures (LCSs), suggests the necessity of integrated
approaches and thus the relevance of design guidelines covering: structure stability and construction
problems, hydro and morphodynamic effects, environmental effects (colonisation of the structure and
water quality), societal and economic impacts (recreational benefits, swimming safety, beach quality).
The present guidelines are specifically dedicated to LCSs to provide methodological tools both for
the engineering design of structures and for prediction of performance and environmental impacts of
such structures. It is anticipated that the guidelines will provide valuable inputs to coastal zone
management plans.
The target audience for this set of guidelines is consulting engineers or engineering officers and
officials of local authorities dealing with coastal protection schemes. The guidelines are also of
relevance in providing a briefing of current best practice for local and national planning authorities,
statutory agencies and other stakeholders in the coastal zone. The guidelines have been drafted in a
generic way to be appropriate throughout the European Union taking into regard current European
Commission policy and directives to promote sustainable development and integrated coastal zone
management.
The guidelines are composed of three main parts.
The first part (Chapters 1-10) contains the description of the design methodology, from the
preliminary identification of design alternatives till the selection of the sustainable scheme and its
construction.
The second part presents:
• the analysis of the performance of beach defences in DELOS study sites, which were selected to
represent a variety of environmental conditions (Chapter 11);
• the application of the proposed methodology to a real prototype case, in order to give a practical
example to designers (Chapter 12).
The third part contains all the formulae and tools to help engineers (Chapter 13), ecologists
(Chapter 14) and economists (Chapter 15) during the design procedure.
The effect of human activities is primarily local but can extend far away from the location of
intervention. This underlines the importance of establishing coastal zone management plans covering
large stretches of coastlines.
The interaction of wave climate, beach erosion, beach defence, habitat changes and beach value,
which clearly exists based on EC research experiences and particularly on results obtained by DELOS
Project (www.delos.unibo.it) for Low Crested Structures (LCSs), suggests the necessity of integrated
approaches and thus the relevance of design guidelines covering: structure stability and construction
problems, hydro and morphodynamic effects, environmental effects (colonisation of the structure and
water quality), societal and economic impacts (recreational benefits, swimming safety, beach quality).
The present guidelines are specifically dedicated to LCSs to provide methodological tools both for
the engineering design of structures and for prediction of performance and environmental impacts of
such structures. It is anticipated that the guidelines will provide valuable inputs to coastal zone
management plans.
The target audience for this set of guidelines is consulting engineers or engineering officers and
officials of local authorities dealing with coastal protection schemes. The guidelines are also of
relevance in providing a briefing of current best practice for local and national planning authorities,
statutory agencies and other stakeholders in the coastal zone. The guidelines have been drafted in a
generic way to be appropriate throughout the European Union taking into regard current European
Commission policy and directives to promote sustainable development and integrated coastal zone
management.
The guidelines are composed of three main parts.
The first part (Chapters 1-10) contains the description of the design methodology, from the
preliminary identification of design alternatives till the selection of the sustainable scheme and its
construction.
The second part presents:
• the analysis of the performance of beach defences in DELOS study sites, which were selected to
represent a variety of environmental conditions (Chapter 11);
• the application of the proposed methodology to a real prototype case, in order to give a practical
example to designers (Chapter 12).
The third part contains all the formulae and tools to help engineers (Chapter 13), ecologists
(Chapter 14) and economists (Chapter 15) during the design procedure.
Contents
Part I
Guidelines
1. Definition of LCSs covered by the guidelines ...................................................................... 3
2. Function of LCSs .................................................................................................................... 5
2.1. LCSs interaction with waves, currents and sediment transport ....................................... 5
2.2. Environmental considerations and consequences ............................................................ 8
2.3. Socio-economic impact of LCSs ..................................................................................... 10
3. Objectives and target effects of LCSs ................................................................................... 11
3.1. Protection of land and infrastructure by prevention or reduction of coastal erosion ....... 11
3.2. Improvement of recreational conditions .......................................................................... 11
3.3. Protect and minimise impacts on cultural and natural heritage of the coastline .............. 12
3.4. Enhancement of natural living resources for food and recreation ................................... 13
4. Outline of design procedure ................................................................................................... 15
5. Initial considerations .............................................................................................................. 17
5.1. Consideration of legal, physical, environmental, socio-economic and aesthetic con-
straints .............................................................................................................................. 17
5.1.1. Relevant policy and legislation .............................................................................. 17
5.1.2. Physical constraints ................................................................................................ 20
5.1.3. Ecological constraints (including ecosystems, natural heritage and living resources) 20
5.1.4. Aesthetic constraints .............................................................................................. 21
5.2. Definition of the primary objectives ................................................................................ 22
5.2.1. Technical objectives .............................................................................................. 22
5.2.2. Environmental objectives ...................................................................................... 22
5.2.3. Socio-economic objectives .................................................................................... 22
5.3. Consideration of LCSs as a possible contribution to a functional and economical solution 23
5.4. Consideration of project service lifetime and structure safety classification .................. 23
5.5. Consideration of environmental context including ecosystem, natural heritage and
natural resources .............................................................................................................. 24
5.6. Synthesis of «Go/No Go» decision .................................................................................. 24
6. Investigation of environmental conditions ......................................................................... 25
6.1. Bathymetry and topography including seasonal and long-term variations .................... 25
6.2. Geology including characterization of surface layers (sediments) ................................. 26
6.3. Water level variations ..................................................................................................... 26
6.4. Wave statistics ................................................................................................................ 27
6.5. Current statistics including tidal, bathymetric and wave generated currents, residual
large-scale currents ......................................................................................................... 28
6.6. Wind statistics, solar exposure and precipitation ........................................................... 29
6.7. Sediment transport by waves and wind .......................................................................... 29
6.8. Sediment characteristics ................................................................................................. 30
6.9. Hydrographic parameters including water quality ......................................................... 31
6.10. Ecological conditions (ecosystem, habitat and species) ................................................. 31
7. Conceptual/pre-design alternatives .................................................................................... 33
7.1. Proposals for lay-out and cross sections of potential LCS schemes ............................... 33
7.2. Preliminary estimation of morphological impact by the use of empirical diagrams, for-
mulae or experience ........................................................................................................ 35
7.3. Structural safety of predesign ......................................................................................... 38
7.4. Identification of environmental conditions for predesign .............................................. 39
7.5. Structural design of LCSs based on material supply possibilities, formulae for stability,
and semi-empirical information on scour ....................................................................... 40
7.6. Assessment of environmental impacts (EIA) at local and regional scale ....................... 42
7.7. Evaluation of the schemes based on economical optimisation ....................................... 43
7.8. Socio-economic evaluation of the schemes ................................................................... 44
7.9. Integration of technical, ecological and economic evaluation for selection of the
sustainable scheme ......................................................................................................... 44
8. Detailed design of preferred scheme .................................................................................. 47
8.1. Optimization of lay-out and cross sections of LCSs based on short-term and long-term
morphodynamic simulations ........................................................................................... 47
8.2. Structural design by the use of formulae and model tests .............................................. 50
8.3. Statement of socio-environmental impacts ..................................................................... 50
8.3.1. Impacts on soft-bottoms (habitats and associated biota) ...................................... 51
8.3.2. Implications for hard-substrate assemblages ........................................................ 51
8.3.3. Impacts on water quality ........................................................................................ 52
8.3.4. Impacts on safety issues ........................................................................................ 52
8.4. Design mitigation measures ............................................................................................ 52
8.5. Identification of design options that maximise specific secondary management goals .... 54
8.5.1. Tools to maximise recreational activities ............................................................. 54
8.5.2. Tools to maximise diversity of species (e.g. for recreational or commercial
purposes) ........................................................................................................................ 55
8.5.3. Tools for minimising growth of ephemeral green algae ....................................... 56
8.6. Evaluation of initial and maintenance costs ................................................................... 56
8.7. Formulation of monitoring programmes ........................................................................ 59
8.8. Maintenance plan ............................................................................................................61
9. Materials for LCSs ............................................................................................................... 63
9.1. Natural rock .................................................................................................................... 63
9.2. Concrete .......................................................................................................................... 64
9.3. Geotextiles ...................................................................................................................... 64
9.4. Environmental considerations ........................................................................................ 65
10. Construction of LCSs ........................................................................................................... 67
10.1. Construction methods .................................................................................................... 67
10.2. Environmental impacts during construction operations ................................................ 70
Part II
– Appendix –
11. Case Studies ........................................................................................................................ 73
11.1. Elmer ......................................................................................................................... 73
11.1.1. Introduction ..................................................................................................... 73
11.1.2. The defence scheme ........................................................................................ 75
11.1.3. Environmental setting ..................................................................................... 77
11.1.4. Environmental effects of Elmer defence scheme ........................................... 78
11.1.5. Conclusions ..................................................................................................... 92
11.2. Altafulla ...................................................................................................................... 93
11.2.1. Introduction and background .......................................................................... 93
11.2.2. Description of the defence scheme ................................................................. 93
11.2.3. Hydrodynamics and sediment regime ............................................................ 95
11.2.4. Effects on hydrodynamics/sediment transport of the Altafulla LCS .............. 96
11.2.5. Effects of the Altafulla LCS on the existing populations, colonisation and
biodiversity ..................................................................................................... 100
11.3. Pellestrina ................................................................................................................... 104
11.3.1. The site ............................................................................................................ 104
11.3.2. Environmental conditions ............................................................................... 104
11.3.3. The defence scheme ........................................................................................ 106
11.3.4. Currents induced by the composite intervention ............................................ 110
11.3.5. Beach evolution after the composite intervention .......................................... 110
11.3.6. Ecological effects induced by the composite interventions ............................ 111
11.3.7. Economic relevance of beach defence ............................................................ 112
11.3.8. Conclusions ..................................................................................................... 114
11.4. Lido di Dante .............................................................................................................. 116
11.4.1. The site ............................................................................................................ 116
11.4.2. Environmental conditions ............................................................................... 116
11.4.3. The defence scheme ........................................................................................ 118
11.4.4. Currents induced by LCS ................................................................................ 120
11.4.5. Beach evolution .............................................................................................. 120
11.4.6. Ecological effects induced by LCSs ............................................................... 124
11.4.7. Economic relevance of beach defence ............................................................ 127
11.4.8. Conclusions ..................................................................................................... 128
11.5. Ostia ......................................................................................................................... 128
11.5.1. Introduction ..................................................................................................... 128
11.5.2. The perched beach project .............................................................................. 129
11.5.3. Monitoring programme ................................................................................... 130
11.5.4. Analysis and observations on beach morphology and rock mound ............... 131
11.5.5. Socio-economic investigations ....................................................................... 136
11.5.6. Ecological aspects ........................................................................................... 136
12. An example of environmental design of coastal defence ................................................ 137
12.1. Preface ........................................................................................................................ 137
12.2. Initial considerations ................................................................................................... 137
12.2.1. Relevant policy and legislation ....................................................................... 137
12.2.2. EIA Constraints .............................................................................................. 139
12.2.3. Definition of technical, environmental, and socio-economic objectives ........ 139
12.2.4. Project service lifetime and safety classification ............................................ 139
12.2.5. Consideration of environmental context ......................................................... 140
12.2.6. Status, vulnerability, sensitivity and resilience of coastal ecosystem ............ 141
12.3. Environmental conditions ........................................................................................... 142
12.3.1. Bathymetry, topology and geology ................................................................. 142
12.3.2. Wind and Wave climate .................................................................................. 143
12.3.3. Currents ........................................................................................................... 144
12.3.4. Water level ...................................................................................................... 144
12.3.5. Sediment transport by winds and waves ......................................................... 144
12.3.6. Water quality .................................................................................................. 145
12.3.7. Ecosystems, habitat and species ..................................................................... 146
12.4. Conceptual pre-design alternatives ............................................................................. 147
12.4.1. Definition of local conditions and constraints ................................................ 147
12.4.2. Identification of alternatives ........................................................................... 147
12.4.3. Preliminary investigation of design alternatives ............................................. 148
12.4.4. Structural design ............................................................................................. 155
12.4.5. Analysis of waves, currents and sediment transport induced by each design
alternative by means of 2DH numerical simulations ...................................... 157
12.4.6. Construction costs ........................................................................................... 176
12.4.7. Ecological comments to design alternatives ................................................... 178
12.4.8. Socio-economic comments to design alternatives .......................................... 182
12.5. Selection of the sustainable scheme ........................................................................... 185
12.6. Detailed design ........................................................................................................... 187
12.6.1. Optimisation of functional design .................................................................. 187
12.6.2. Structural design ............................................................................................. 188
12.6.3. Verification of expected optimisations ........................................................... 194
12.6.4. Maintenance plan ............................................................................................ 194
12.6.5. Monitoring plan .............................................................................................. 198
12.6.6. Recommendations for construction phase ...................................................... 198
12.7. Conclusions ................................................................................................................. 198
Part III
– Tools –
13. Design tools related to engineering ................................................................................... 203
13.1. Site condition parameters ........................................................................................... 203
13.1.1. Bathymetry and morphology .......................................................................... 203
13.1.2. Water levels, waves and currents .................................................................... 204
13.1.3. Extreme events analysis .................................................................................. 207
13.2. Transformation of waves from deep water to shallow water ..................................... 212
13.2.1. Basic concepts ................................................................................................ 213
13.2.2. Energy conservation ....................................................................................... 213
13.2.3. Wave energy dissipation ................................................................................. 215
13.2.4. Technical methods for irregular wave decay .................................................. 219
13.2.5. Wave height distribution in shallow water ..................................................... 220
13.3. Wave transformation by structures ............................................................................. 223
13.3.1. Wave transmission .......................................................................................... 224
13.3.2. Wave reflection ............................................................................................... 231
13.4. Hydrodynamic numerical models to predict local hydrodynamics in the vicinity of
the structures ............................................................................................................... 233
13.4.1. Introduction and concepts ............................................................................... 233
13.4.2. Types of models and modelling ...................................................................... 233
13.4.3. Numerical modelling systems available for engineering applications ........... 237
13.4.4. Flow modelling tools ...................................................................................... 237
13.4.5. Wave modelling tools ..................................................................................... 245
13.4.6. Fluid dynamics modelling tools ...................................................................... 254
13.4.7. Other modelling tools ..................................................................................... 260
13.5. Prediction of wave induced water flow over and through the structure, of set-up
and rip-currents ........................................................................................................... 262
13.5.1. Introduction ..................................................................................................... 262
13.5.2. Wave mass flux, overtopping ......................................................................... 263
13.5.3. Piling-up ......................................................................................................... 267
13.5.4. Return-flows ................................................................................................... 273
13.5.5. Verification of the circulation model .............................................................. 278
13.6. Cross-shore equilibrium profile .................................................................................. 280
13.6.1. Introduction ..................................................................................................... 280
13.6.2. Perched beaches .............................................................................................. 281
13.6.3. Reef-protected beaches ................................................................................... 282
13.7. Cross-shore sediment transport ................................................................................... 284
13.8. Long-shore sediment transport (amount and distribution over the coastal profile) .... 286
13.9. Empirical diagrams/formulae for prediction of formation of salients and tombolos ..... 289
13.9.1. Introduction ..................................................................................................... 289
13.9.2. Proposed methodology for emerged breakwaters ........................................... 289
13.9.3. Tombolo and salient prediction for emerged breakwaters ............................. 293
13.9.4. Submerged breakwaters .................................................................................. 297
13.10. Combined hydrodynamic and morphologic numerical models to predict short and
long-term spatial and temporal effects .................................................................... 298
13.10.1. Processes under simulation ............................................................................ 298
13.10.2. Model classification ...................................................................................... 299
13.10.3. 2DH and Q3D models .................................................................................. 301
13.10.4. One and multi-line models ............................................................................ 305
13.11. Formulae for structural stability ................................................................................ 307
13.11.1. Hydraulic armour layer stability ................................................................... 307
13.11.2. Bedding layer and geotextiles ....................................................................... 321
13.11.3. Toe berm stability ......................................................................................... 324
13.11.4. Dimension of scour protection ...................................................................... 326
13.12. Model tests related to structure design ..................................................................... 329
13.13. Safety aspects ............................................................................................................ 330
13.13.1. Limit states for maritime structures .............................................................. 330
13.13.2. LCS limit states and failure modes ............................................................... 332
14. Background knowledge and tools for prediction of ecological impacts ........................ 335
14.1. Definitions of main factors influencing the distribution and abundance of species
and assemblages (biotopes) on natural soft- and rocky bottoms ................................ 335
14.1.1. Broad-scale – Geographic variation ................................................................ 335
14.1.2. Mesoscale – Within coastline ......................................................................... 335
14.1.3. Local scale – Major abiotic factors and processes .......................................... 337
14.1.4. Local scale – Biological interactions and behaviour ...................................... 338
14.1.5. Micro scale – Complexity ............................................................................... 339
14.1.6. Human activities ............................................................................................. 339
14.2. Tools for assessment of impacts ................................................................................. 341
14.2.1. Rapid field assessment protocol for evaluation of ecological conditions of
the proposed LCS ........................................................................................... 341
14.2.2. Baseline ecological surveys ............................................................................ 343
14.2.3. A biotope model for prediction of impacts on soft-bottoms ........................... 344
15. Design tools related to socio-economics ............................................................................ 347
15.1. General description of cost benefit analysis ............................................................... 347
15.2. Classification of costs and benefits and inventory of coastal assets ........................... 348
15.2.1. Principle of economic value and typology of values ...................................... 348
15.2.2. Overview of the valuation techniques ............................................................ 349
15.2.3. Typologies of coastal assets ............................................................................ 350
15.2.4. Indicative values per type of coastal asset ...................................................... 352
15.3. Transfer of empirical values ....................................................................................... 354
15.3.1. Data sets .......................................................................................................... 354
15.3.2. Regression models and transfer ...................................................................... 356
15.4. Non-marketable recreational use value of a beach ..................................................... 358
15.4.1. Introduction ..................................................................................................... 358
15.4.2. Methodology used for the Italian case-studies: the questionnaire .................. 359
15.4.3. The use value according to seasons ................................................................ 360
15.4.4. Use value for foreigners and aggregation level .............................................. 361
15.4.5. Conclusions ..................................................................................................... 362
15.5. The benefit of protection of land/hinterland ............................................................... 363
15.5.1. Risk and Vulnerability .................................................................................... 363
15.6. The value of habitat disruption ................................................................................... 366
15.7. Options use and non-use values of a coastal cultural heritage ................................... 369
15.7.1. Introduction ..................................................................................................... 369
15.7.2. Aggregation level: the international community ............................................ 369
15.7.3. The CVM questionnaire: the probability of paying ........................................ 370
15.7.4. The option use and non-use values of visitors in Venice ............................... 370
15.7.5. Conclusion ...................................................................................................... 372
15.8. Visitors preferences about beach defence techniques and beach materials ................ 372
15.8.1. Introduction ..................................................................................................... 372
15.8.2. Questions on kinds of defence structures and beach materials ....................... 372
15.8.3. Conclusion ...................................................................................................... 374
References ................................................................................................................................. 375
Index ....................................................................................................................................... 397
by Hans F. Burcharth
Stephen J. Hawkins
Barbara Zanuttigh
Alberto Lamberti
Pages: 419
Publisher:
Edition: 1st, December 4, 2007
Language: English
ASIN: B0086QJXT4
Description
The effect of human activities is primarily local but can extend far away from the location of
intervention. This underlines the importance of establishing coastal zone management plans covering
large stretches of coastlines.
The interaction of wave climate, beach erosion, beach defence, habitat changes and beach value,
which clearly exists based on EC research experiences and particularly on results obtained by DELOS
Project (www.delos.unibo.it) for Low Crested Structures (LCSs), suggests the necessity of integrated
approaches and thus the relevance of design guidelines covering: structure stability and construction
problems, hydro and morphodynamic effects, environmental effects (colonisation of the structure and
water quality), societal and economic impacts (recreational benefits, swimming safety, beach quality).
The present guidelines are specifically dedicated to LCSs to provide methodological tools both for
the engineering design of structures and for prediction of performance and environmental impacts of
such structures. It is anticipated that the guidelines will provide valuable inputs to coastal zone
management plans.
The target audience for this set of guidelines is consulting engineers or engineering officers and
officials of local authorities dealing with coastal protection schemes. The guidelines are also of
relevance in providing a briefing of current best practice for local and national planning authorities,
statutory agencies and other stakeholders in the coastal zone. The guidelines have been drafted in a
generic way to be appropriate throughout the European Union taking into regard current European
Commission policy and directives to promote sustainable development and integrated coastal zone
management.
The guidelines are composed of three main parts.
The first part (Chapters 1-10) contains the description of the design methodology, from the
preliminary identification of design alternatives till the selection of the sustainable scheme and its
construction.
The second part presents:
• the analysis of the performance of beach defences in DELOS study sites, which were selected to
represent a variety of environmental conditions (Chapter 11);
• the application of the proposed methodology to a real prototype case, in order to give a practical
example to designers (Chapter 12).
The third part contains all the formulae and tools to help engineers (Chapter 13), ecologists
(Chapter 14) and economists (Chapter 15) during the design procedure.
The effect of human activities is primarily local but can extend far away from the location of
intervention. This underlines the importance of establishing coastal zone management plans covering
large stretches of coastlines.
The interaction of wave climate, beach erosion, beach defence, habitat changes and beach value,
which clearly exists based on EC research experiences and particularly on results obtained by DELOS
Project (www.delos.unibo.it) for Low Crested Structures (LCSs), suggests the necessity of integrated
approaches and thus the relevance of design guidelines covering: structure stability and construction
problems, hydro and morphodynamic effects, environmental effects (colonisation of the structure and
water quality), societal and economic impacts (recreational benefits, swimming safety, beach quality).
The present guidelines are specifically dedicated to LCSs to provide methodological tools both for
the engineering design of structures and for prediction of performance and environmental impacts of
such structures. It is anticipated that the guidelines will provide valuable inputs to coastal zone
management plans.
The target audience for this set of guidelines is consulting engineers or engineering officers and
officials of local authorities dealing with coastal protection schemes. The guidelines are also of
relevance in providing a briefing of current best practice for local and national planning authorities,
statutory agencies and other stakeholders in the coastal zone. The guidelines have been drafted in a
generic way to be appropriate throughout the European Union taking into regard current European
Commission policy and directives to promote sustainable development and integrated coastal zone
management.
The guidelines are composed of three main parts.
The first part (Chapters 1-10) contains the description of the design methodology, from the
preliminary identification of design alternatives till the selection of the sustainable scheme and its
construction.
The second part presents:
• the analysis of the performance of beach defences in DELOS study sites, which were selected to
represent a variety of environmental conditions (Chapter 11);
• the application of the proposed methodology to a real prototype case, in order to give a practical
example to designers (Chapter 12).
The third part contains all the formulae and tools to help engineers (Chapter 13), ecologists
(Chapter 14) and economists (Chapter 15) during the design procedure.
Contents
Part I
Guidelines
1. Definition of LCSs covered by the guidelines ...................................................................... 3
2. Function of LCSs .................................................................................................................... 5
2.1. LCSs interaction with waves, currents and sediment transport ....................................... 5
2.2. Environmental considerations and consequences ............................................................ 8
2.3. Socio-economic impact of LCSs ..................................................................................... 10
3. Objectives and target effects of LCSs ................................................................................... 11
3.1. Protection of land and infrastructure by prevention or reduction of coastal erosion ....... 11
3.2. Improvement of recreational conditions .......................................................................... 11
3.3. Protect and minimise impacts on cultural and natural heritage of the coastline .............. 12
3.4. Enhancement of natural living resources for food and recreation ................................... 13
4. Outline of design procedure ................................................................................................... 15
5. Initial considerations .............................................................................................................. 17
5.1. Consideration of legal, physical, environmental, socio-economic and aesthetic con-
straints .............................................................................................................................. 17
5.1.1. Relevant policy and legislation .............................................................................. 17
5.1.2. Physical constraints ................................................................................................ 20
5.1.3. Ecological constraints (including ecosystems, natural heritage and living resources) 20
5.1.4. Aesthetic constraints .............................................................................................. 21
5.2. Definition of the primary objectives ................................................................................ 22
5.2.1. Technical objectives .............................................................................................. 22
5.2.2. Environmental objectives ...................................................................................... 22
5.2.3. Socio-economic objectives .................................................................................... 22
5.3. Consideration of LCSs as a possible contribution to a functional and economical solution 23
5.4. Consideration of project service lifetime and structure safety classification .................. 23
5.5. Consideration of environmental context including ecosystem, natural heritage and
natural resources .............................................................................................................. 24
5.6. Synthesis of «Go/No Go» decision .................................................................................. 24
6. Investigation of environmental conditions ......................................................................... 25
6.1. Bathymetry and topography including seasonal and long-term variations .................... 25
6.2. Geology including characterization of surface layers (sediments) ................................. 26
6.3. Water level variations ..................................................................................................... 26
6.4. Wave statistics ................................................................................................................ 27
6.5. Current statistics including tidal, bathymetric and wave generated currents, residual
large-scale currents ......................................................................................................... 28
6.6. Wind statistics, solar exposure and precipitation ........................................................... 29
6.7. Sediment transport by waves and wind .......................................................................... 29
6.8. Sediment characteristics ................................................................................................. 30
6.9. Hydrographic parameters including water quality ......................................................... 31
6.10. Ecological conditions (ecosystem, habitat and species) ................................................. 31
7. Conceptual/pre-design alternatives .................................................................................... 33
7.1. Proposals for lay-out and cross sections of potential LCS schemes ............................... 33
7.2. Preliminary estimation of morphological impact by the use of empirical diagrams, for-
mulae or experience ........................................................................................................ 35
7.3. Structural safety of predesign ......................................................................................... 38
7.4. Identification of environmental conditions for predesign .............................................. 39
7.5. Structural design of LCSs based on material supply possibilities, formulae for stability,
and semi-empirical information on scour ....................................................................... 40
7.6. Assessment of environmental impacts (EIA) at local and regional scale ....................... 42
7.7. Evaluation of the schemes based on economical optimisation ....................................... 43
7.8. Socio-economic evaluation of the schemes ................................................................... 44
7.9. Integration of technical, ecological and economic evaluation for selection of the
sustainable scheme ......................................................................................................... 44
8. Detailed design of preferred scheme .................................................................................. 47
8.1. Optimization of lay-out and cross sections of LCSs based on short-term and long-term
morphodynamic simulations ........................................................................................... 47
8.2. Structural design by the use of formulae and model tests .............................................. 50
8.3. Statement of socio-environmental impacts ..................................................................... 50
8.3.1. Impacts on soft-bottoms (habitats and associated biota) ...................................... 51
8.3.2. Implications for hard-substrate assemblages ........................................................ 51
8.3.3. Impacts on water quality ........................................................................................ 52
8.3.4. Impacts on safety issues ........................................................................................ 52
8.4. Design mitigation measures ............................................................................................ 52
8.5. Identification of design options that maximise specific secondary management goals .... 54
8.5.1. Tools to maximise recreational activities ............................................................. 54
8.5.2. Tools to maximise diversity of species (e.g. for recreational or commercial
purposes) ........................................................................................................................ 55
8.5.3. Tools for minimising growth of ephemeral green algae ....................................... 56
8.6. Evaluation of initial and maintenance costs ................................................................... 56
8.7. Formulation of monitoring programmes ........................................................................ 59
8.8. Maintenance plan ............................................................................................................61
9. Materials for LCSs ............................................................................................................... 63
9.1. Natural rock .................................................................................................................... 63
9.2. Concrete .......................................................................................................................... 64
9.3. Geotextiles ...................................................................................................................... 64
9.4. Environmental considerations ........................................................................................ 65
10. Construction of LCSs ........................................................................................................... 67
10.1. Construction methods .................................................................................................... 67
10.2. Environmental impacts during construction operations ................................................ 70
Part II
– Appendix –
11. Case Studies ........................................................................................................................ 73
11.1. Elmer ......................................................................................................................... 73
11.1.1. Introduction ..................................................................................................... 73
11.1.2. The defence scheme ........................................................................................ 75
11.1.3. Environmental setting ..................................................................................... 77
11.1.4. Environmental effects of Elmer defence scheme ........................................... 78
11.1.5. Conclusions ..................................................................................................... 92
11.2. Altafulla ...................................................................................................................... 93
11.2.1. Introduction and background .......................................................................... 93
11.2.2. Description of the defence scheme ................................................................. 93
11.2.3. Hydrodynamics and sediment regime ............................................................ 95
11.2.4. Effects on hydrodynamics/sediment transport of the Altafulla LCS .............. 96
11.2.5. Effects of the Altafulla LCS on the existing populations, colonisation and
biodiversity ..................................................................................................... 100
11.3. Pellestrina ................................................................................................................... 104
11.3.1. The site ............................................................................................................ 104
11.3.2. Environmental conditions ............................................................................... 104
11.3.3. The defence scheme ........................................................................................ 106
11.3.4. Currents induced by the composite intervention ............................................ 110
11.3.5. Beach evolution after the composite intervention .......................................... 110
11.3.6. Ecological effects induced by the composite interventions ............................ 111
11.3.7. Economic relevance of beach defence ............................................................ 112
11.3.8. Conclusions ..................................................................................................... 114
11.4. Lido di Dante .............................................................................................................. 116
11.4.1. The site ............................................................................................................ 116
11.4.2. Environmental conditions ............................................................................... 116
11.4.3. The defence scheme ........................................................................................ 118
11.4.4. Currents induced by LCS ................................................................................ 120
11.4.5. Beach evolution .............................................................................................. 120
11.4.6. Ecological effects induced by LCSs ............................................................... 124
11.4.7. Economic relevance of beach defence ............................................................ 127
11.4.8. Conclusions ..................................................................................................... 128
11.5. Ostia ......................................................................................................................... 128
11.5.1. Introduction ..................................................................................................... 128
11.5.2. The perched beach project .............................................................................. 129
11.5.3. Monitoring programme ................................................................................... 130
11.5.4. Analysis and observations on beach morphology and rock mound ............... 131
11.5.5. Socio-economic investigations ....................................................................... 136
11.5.6. Ecological aspects ........................................................................................... 136
12. An example of environmental design of coastal defence ................................................ 137
12.1. Preface ........................................................................................................................ 137
12.2. Initial considerations ................................................................................................... 137
12.2.1. Relevant policy and legislation ....................................................................... 137
12.2.2. EIA Constraints .............................................................................................. 139
12.2.3. Definition of technical, environmental, and socio-economic objectives ........ 139
12.2.4. Project service lifetime and safety classification ............................................ 139
12.2.5. Consideration of environmental context ......................................................... 140
12.2.6. Status, vulnerability, sensitivity and resilience of coastal ecosystem ............ 141
12.3. Environmental conditions ........................................................................................... 142
12.3.1. Bathymetry, topology and geology ................................................................. 142
12.3.2. Wind and Wave climate .................................................................................. 143
12.3.3. Currents ........................................................................................................... 144
12.3.4. Water level ...................................................................................................... 144
12.3.5. Sediment transport by winds and waves ......................................................... 144
12.3.6. Water quality .................................................................................................. 145
12.3.7. Ecosystems, habitat and species ..................................................................... 146
12.4. Conceptual pre-design alternatives ............................................................................. 147
12.4.1. Definition of local conditions and constraints ................................................ 147
12.4.2. Identification of alternatives ........................................................................... 147
12.4.3. Preliminary investigation of design alternatives ............................................. 148
12.4.4. Structural design ............................................................................................. 155
12.4.5. Analysis of waves, currents and sediment transport induced by each design
alternative by means of 2DH numerical simulations ...................................... 157
12.4.6. Construction costs ........................................................................................... 176
12.4.7. Ecological comments to design alternatives ................................................... 178
12.4.8. Socio-economic comments to design alternatives .......................................... 182
12.5. Selection of the sustainable scheme ........................................................................... 185
12.6. Detailed design ........................................................................................................... 187
12.6.1. Optimisation of functional design .................................................................. 187
12.6.2. Structural design ............................................................................................. 188
12.6.3. Verification of expected optimisations ........................................................... 194
12.6.4. Maintenance plan ............................................................................................ 194
12.6.5. Monitoring plan .............................................................................................. 198
12.6.6. Recommendations for construction phase ...................................................... 198
12.7. Conclusions ................................................................................................................. 198
Part III
– Tools –
13. Design tools related to engineering ................................................................................... 203
13.1. Site condition parameters ........................................................................................... 203
13.1.1. Bathymetry and morphology .......................................................................... 203
13.1.2. Water levels, waves and currents .................................................................... 204
13.1.3. Extreme events analysis .................................................................................. 207
13.2. Transformation of waves from deep water to shallow water ..................................... 212
13.2.1. Basic concepts ................................................................................................ 213
13.2.2. Energy conservation ....................................................................................... 213
13.2.3. Wave energy dissipation ................................................................................. 215
13.2.4. Technical methods for irregular wave decay .................................................. 219
13.2.5. Wave height distribution in shallow water ..................................................... 220
13.3. Wave transformation by structures ............................................................................. 223
13.3.1. Wave transmission .......................................................................................... 224
13.3.2. Wave reflection ............................................................................................... 231
13.4. Hydrodynamic numerical models to predict local hydrodynamics in the vicinity of
the structures ............................................................................................................... 233
13.4.1. Introduction and concepts ............................................................................... 233
13.4.2. Types of models and modelling ...................................................................... 233
13.4.3. Numerical modelling systems available for engineering applications ........... 237
13.4.4. Flow modelling tools ...................................................................................... 237
13.4.5. Wave modelling tools ..................................................................................... 245
13.4.6. Fluid dynamics modelling tools ...................................................................... 254
13.4.7. Other modelling tools ..................................................................................... 260
13.5. Prediction of wave induced water flow over and through the structure, of set-up
and rip-currents ........................................................................................................... 262
13.5.1. Introduction ..................................................................................................... 262
13.5.2. Wave mass flux, overtopping ......................................................................... 263
13.5.3. Piling-up ......................................................................................................... 267
13.5.4. Return-flows ................................................................................................... 273
13.5.5. Verification of the circulation model .............................................................. 278
13.6. Cross-shore equilibrium profile .................................................................................. 280
13.6.1. Introduction ..................................................................................................... 280
13.6.2. Perched beaches .............................................................................................. 281
13.6.3. Reef-protected beaches ................................................................................... 282
13.7. Cross-shore sediment transport ................................................................................... 284
13.8. Long-shore sediment transport (amount and distribution over the coastal profile) .... 286
13.9. Empirical diagrams/formulae for prediction of formation of salients and tombolos ..... 289
13.9.1. Introduction ..................................................................................................... 289
13.9.2. Proposed methodology for emerged breakwaters ........................................... 289
13.9.3. Tombolo and salient prediction for emerged breakwaters ............................. 293
13.9.4. Submerged breakwaters .................................................................................. 297
13.10. Combined hydrodynamic and morphologic numerical models to predict short and
long-term spatial and temporal effects .................................................................... 298
13.10.1. Processes under simulation ............................................................................ 298
13.10.2. Model classification ...................................................................................... 299
13.10.3. 2DH and Q3D models .................................................................................. 301
13.10.4. One and multi-line models ............................................................................ 305
13.11. Formulae for structural stability ................................................................................ 307
13.11.1. Hydraulic armour layer stability ................................................................... 307
13.11.2. Bedding layer and geotextiles ....................................................................... 321
13.11.3. Toe berm stability ......................................................................................... 324
13.11.4. Dimension of scour protection ...................................................................... 326
13.12. Model tests related to structure design ..................................................................... 329
13.13. Safety aspects ............................................................................................................ 330
13.13.1. Limit states for maritime structures .............................................................. 330
13.13.2. LCS limit states and failure modes ............................................................... 332
14. Background knowledge and tools for prediction of ecological impacts ........................ 335
14.1. Definitions of main factors influencing the distribution and abundance of species
and assemblages (biotopes) on natural soft- and rocky bottoms ................................ 335
14.1.1. Broad-scale – Geographic variation ................................................................ 335
14.1.2. Mesoscale – Within coastline ......................................................................... 335
14.1.3. Local scale – Major abiotic factors and processes .......................................... 337
14.1.4. Local scale – Biological interactions and behaviour ...................................... 338
14.1.5. Micro scale – Complexity ............................................................................... 339
14.1.6. Human activities ............................................................................................. 339
14.2. Tools for assessment of impacts ................................................................................. 341
14.2.1. Rapid field assessment protocol for evaluation of ecological conditions of
the proposed LCS ........................................................................................... 341
14.2.2. Baseline ecological surveys ............................................................................ 343
14.2.3. A biotope model for prediction of impacts on soft-bottoms ........................... 344
15. Design tools related to socio-economics ............................................................................ 347
15.1. General description of cost benefit analysis ............................................................... 347
15.2. Classification of costs and benefits and inventory of coastal assets ........................... 348
15.2.1. Principle of economic value and typology of values ...................................... 348
15.2.2. Overview of the valuation techniques ............................................................ 349
15.2.3. Typologies of coastal assets ............................................................................ 350
15.2.4. Indicative values per type of coastal asset ...................................................... 352
15.3. Transfer of empirical values ....................................................................................... 354
15.3.1. Data sets .......................................................................................................... 354
15.3.2. Regression models and transfer ...................................................................... 356
15.4. Non-marketable recreational use value of a beach ..................................................... 358
15.4.1. Introduction ..................................................................................................... 358
15.4.2. Methodology used for the Italian case-studies: the questionnaire .................. 359
15.4.3. The use value according to seasons ................................................................ 360
15.4.4. Use value for foreigners and aggregation level .............................................. 361
15.4.5. Conclusions ..................................................................................................... 362
15.5. The benefit of protection of land/hinterland ............................................................... 363
15.5.1. Risk and Vulnerability .................................................................................... 363
15.6. The value of habitat disruption ................................................................................... 366
15.7. Options use and non-use values of a coastal cultural heritage ................................... 369
15.7.1. Introduction ..................................................................................................... 369
15.7.2. Aggregation level: the international community ............................................ 369
15.7.3. The CVM questionnaire: the probability of paying ........................................ 370
15.7.4. The option use and non-use values of visitors in Venice ............................... 370
15.7.5. Conclusion ...................................................................................................... 372
15.8. Visitors preferences about beach defence techniques and beach materials ................ 372
15.8.1. Introduction ..................................................................................................... 372
15.8.2. Questions on kinds of defence structures and beach materials ....................... 372
15.8.3. Conclusion ...................................................................................................... 374
References ................................................................................................................................. 375
Index ....................................................................................................................................... 397
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