Overview of soft coastal protection solutions Atlantic Network for Coastal Risks Management Galicia (Spain) Contents Introduction 03 1 - Atlantic coastline erosion 07 Beaches 08 Dunes 09 Cliffs 12 Tidal marshes 16 2 - Soft coastal protection solutions 21 Discussion on the limitations of "hard" and "soft" methods 21 "Soft" solutions 22 3 - Decision support to develop a management strategy to address coastal erosion 49 Managing coastal protection 49 Decision tree 53 Conclusion 54 References 54 2 // Overview of soft coastal protection solutions introduction Rich and varied littoral but fragile Roughly 16% of the European population lives ronments and their functioning in the coastal and coveted in coastal communities. This proportion is ever ecosystem. increasing. However, this human presence has The littoral is a fragile and mobile area at the clearly affected the littoral environment. In Beach, cliff and coastline erosion as well as interface of the atmosphere, lithosphere and general, economic activities increase pressure receding shorelines and the risks of marine hydrosphere. The evolution of littoral environ- on coastal zones (increase in number of buil- submergence are preoccupying subjects that ments depends on continental factors (geolo- dings, beach sediment extraction, intensive are becoming more important for European gical structure), marine factors (variations of tourist use of coastal areas, etc. ). Residential, shoreline communities (20% of the European the mean sea level, processes brought about by touristic and economic attractiveness is stea- Union coasts are affected by this phenome- waves, tide and induced currents) and atmos- dily growing on the European Atlantic coast. non), because of increased stakes, and parti- pheric factors (subaerial agents). Varying com- Coastal zones have large ecological, social cularly economic stakes in zones affected by binations of these factors change shoreline po- and economic functions and it is advisable to recurrent natural climatic hazards. sition and coast morphology (beaches, dunes, define a coastal sustainable development plan cliffs, tidal marshes) on various time and space including protecting people, property and scales (diagram 11). activities, while also protecting natural envi- Galicia (Spain) Diagram 1: Concept of time in littoral processes 1 The different notions are expressed in chapter 1. Overview of soft coastal protection solutions // 3 Some essential concepts However, its current magnitude is undeniably their stakes, it is first necessary to unders- linked to anthropogenic factors. tand the interest and role of natural littoral A hazard is the probability of occurrence of In many sites, solutions to mitigate this phe- infrastructures such as dunes, cliffs and coas- a potentially damaging phenomenon within nomenon, such as the construction of heavy tal marshes, and wherever possible, envisage a given time period and area. The coasts are protection structures, have aggravated erosion "soft" solutions designed to work with nature mainly subject to risks such as erosion, marine on areas requiring protection and neighbou- by integrating natural coastal dynamics and flooding and landslides. ring shorelines. These solutions are used less the mobility of shorelines. Dynamic shoreline A stake is a group of goods, people, systems or frequently with growing preference for soft management is a continuous process which any other element present in a risk area and solutions which are more favourable to the en- oscillates between observation and action and which could be potentially lost. vironment. In addition, the soft infrastructure which lasts for as long as there are stakes ex- Erosion hazard is, by definition, a group of represented by the coast, plays an important posed to coastal risks. A risk is in fact to expect external phenomena, which on the soil sur- role in increasing and preserving biodiversity, losses (lives, injuries, property damage, etc. ) face or at low depth change the topography by which also contributes to coastal protection. due to a particular natural or human-induced matter extraction. Erosion can be natural or Besides, the marine submergence hazard is hazard in a given area and reference period. anthropogenic2. particularly damaging along coasts where the The degree of vulnerability3 and exposure of Coastal erosion occurs when the sea gains concentration of the stakes continues to in- socio-economic or environmental systems to ground on the land under the effects of fac- crease. the hazard are key elements when considering tors such as wind, swell, tides, etc. This natural In order to limit the inevitable phenomenon the severity of potential risks. process has always existed and has shaped the of erosion as well as marine submergence European Atlantic coast throughout history. and thus preserve natural environments and 2 Anthropogenic: result of human activity on the natural environment. 3 Vulnerability: refer to chap. III, A, 1. 4 // Overview of soft coastal protection solutions How can coastal risk management Three pedagogical tools and a glossary were coastal management (decision support tool). be improved? thus developed within this project. Tool n°1 Three kinds of typical European Atlantic coasts deals with coastal risks. Tool n°2 deals with are discussed: sandy and rocky coasts and The European project, ANCORIM, aims to set natural littoral infrastructures and soft solu- coastal marshes. This tool takes as geographi- up a public and scientific stakeholder network tions to protect coastlines threatened by ero- cal reference space the Atlantic space of the for enhanced prevention and management of sion. This document deals with this tool and is European continent, in particular the partner coastal risks in the Atlantic Area. intended for decision-makers and managers. regions of the project Ancorim: Aquitaine, Tool n°3 deals with management and taking Brittany and Poitou-Charentes in France, The project is organized around these risks into consideration for coastal deve- North and Central regions of Portugal, Galicia three main issues: lopment. in Spain and the Border, Midland and Western 1) shoreline erosion and stability, This document initially discusses Atlantic region in Ireland. Other limited examples from 2) coastal water quality and its impact on eco- coastal erosion, then goes on to present a non-partner regions were also included as il- nomic activities, and range of soft solutions for coastal erosion. The lustrative material. 3) rural and urban coastal development. document concludes with a discussion on Rocky coast Overview of soft coastal protection solutions // 5 Galicia (Spain) 6 // Overview of soft coastal protection solutions 1 - atlantic coastline erosion The littoral is an ecologically rich and fra- scales. Its dynamic balance is principally On the European Atlantic littoral, there are gile area. It can experience reversible or due to sediment exchanges and transfers three types of shoreline: the sandy coast, irreversible developments under the in- at the interface between marine and conti- the rocky coast and tidal marshes (wetlands fluence of natural or anthropogenic exter- nental environments (long-shore drift, cliff including estuaries and lagoons). nal agents, in various temporal and spatial erosion, storage in dunes, etc.). Erosion is a natural phenomenon (hazard) - continental agents: in particular hydrology filtration) also contributes to the modifica- created by the combined effects of: by feeding fluvial sediments. These agents tion of littoral shapes; - atmospheric agents: wind, rain, temperature; are mechanical type processes (introduced - biological agents: possible erosive impact of - marine agents: swells, tides, induced cur- by variations in temperature or variations in flora and fauna on hard and soft sediment. rents, sea level (dependant on global war- rock water levels) or physico-chemical pro- ming, tectonic effects, subsidence4, etc. ); cesses (alterations). Precipitation (runoff or Sandy coastlines come from marine as worms). On the Atlantic coastline, functional perspective. Rocky coastlines are sedimentation or from the activity of they include beaches and dunes (photo mainly characterised by coasts with cliffs, organisms (algae and benthic fauna such 1), directly linked from a landscape and and wetlands are principally tidal marshes. The dynamic balance of the shoreline can These infrastructures (mainly wetlands, cliffs also be impacted by sudden variations of and dunes) provide services that are indispen- the sea level (tsunamis, large storms, etc.). sible for managing and developing the littoral Coastlines, also presented as natural littoral and it is for this reason that they should be res- infrastructures, are ecosystems that form an tored and treasured. interface between the marine and terrestrial Europe’s landscape is increasingly fragmented environment whilst providing better pro- and this is a major problem for biodiversity. tection against coastal erosion. In Atlantic The term green infrastructure (European com- Europe, they each have their own identity de- mission website) is used here because these pending on the type of coast and surrounding infrastructures help reconnect existing natu- environmental conditions. ral areas (wetlands, dunes, etc. ) and improve They participate in the coastal dynamic pro- the area’s ecological qualities. They also help cess and make up unique ecosystems with a maintain ecosystem services. high heritage added-value, contributing to the quality of