Sandy shorelines are some of the most extensive intertidal systems worldwide, representing both excellent recreational assets and buffer zones against the sea. Despite their initial barren and sterile appearance, many sandy littoral localities might even be considered as highly productive.
There are several conspicuous parts to a beach that relate to the processes that form and shape it. The part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face — the latter being the slope leading down towards the water from the crest.
The sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (sand size or smaller), winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune.
Dunes are a dynamic, but fragile coastal landform. The changes brought about by the natural processes of winds, waves and tides are rarely gradual or predictable. Rather they are episodic, with periods of little or no change followed by times of intense activity, most obviously during storms when dunes may be eroded rapidly, their seaward faces receding many metres in a few days. Often these events go unnoticed by local residents or land-owners, with subsequent re-building of the dunes by wind action in the following weeks and months. However, when damage occurs with little or no natural restoration of the dunes over a period of several years, then concern arises, especially if there are important assets at risk to the landward. It is usually as a result of such events that intervention works are undertaken, sometimes later proving to be unnecessary or damaging to the natural beach/ dune system.
From the perspective of coastal management dunes protect low lying coastal areas from flooding and also act as a buffer against erosion: they form a reservoir of sand, replenished when beach levels are high and released to nourish the foreshore during storm erosion. They are also areas of considerable scientific, conservation, landscape and recreational value. Because of these attributes they are important to a wide range of human activities, and their management is seen as an important objective in planning and usage of the coastal zone.
The development of the beach as a popular leisure resort from the mid-19th century was the first manifestation of what is now the global tourist industry. The first seaside resorts were opened in the 18th century for the aristocracy, who began to frequent the seaside as well as the then fashionable spa towns, for recreation and health.
Beaches and dunes are changed in shape chiefly by the movement of water and wind. These movements can lead to coastal erosion and coastal flooding. Coast erosion is the process of wearing away material from the coastal profile due to imbalance in the supply and export of material from a certain section. It takes place in the form of scouring in the foot of the cliffs or in the foot of the dunes. Coast erosion takes place mainly during strong winds, high waves and high tides and storm surge conditions, and results in coastline retreat. The rate of erosion is correctly expressed in volume/length/time, e.g. in m3/m/year, but erosion rate is often used synonymously with coastline retreat, and thus expressed in m/year.
Although the sediment balance can be disturbed by natural causes (depletion of the source, a change in the mouth of a river or estuary, gradual shift in wave climate), it is often the result of human activities along an adjacent frontage or nearshore area. These may include dredging, construction of harbour breakwaters, protection of eroding cliffs or construction of beach control structures such as groynes or breakwaters. Erosion in these cases is not natural.
More information on impacts of tourism in coastal areas here.
Groynes are cross-shore structures designed to reduce longshore transport on open beaches or to deflect nearshore currents within an estuary. On an open beach they are normally built as a series to influence a long section of shoreline that has been nourished or is managed by recycling. In an estuary they may be single structures.
A breakwater is a coastal structure (usually a rock and rubble mound structure) projecting into the sea that shelters vessels from waves and currents, prevents siltation of a navigation channel, protects a shore area or prevents thermal mixing (e.g. cooling water intakes). A breakwater typically comprises various stone layers and is typically armoured with large armour stone or concrete armour units (an exception are e.g. vertical (caisson) breakwaters). A breakwater can be built at the shoreline or offshore (detached or reef breakwater). This measure is not directly addressed to protect the coast in flood events, but can indirectly stabilize the coast by preventing erosion.
Not all stakeholders are aware or informed about their vulnerability to a changing climate, or flood risk protection. Nor are they aware of the pro-active measures they can take to adapt or deal with climate change. Awareness raising and education programs are therefore important to manage the impacts of climate change, enhance peoples’ capacity to deal with the impacts, and reduce overall vulnerability.
Sharing knowledge in this way can help build safety and resilience, reduce future hazard impacts. Communities and individuals usually want to become partners in this, and the public can be empowered to deal with the impacts and reduce future problems related to flood risk and disaster risk response.
The main objective of land claim is neither erosion nor storm reduction. The aim of land claim is to create new land from areas that were previously below high tide. These measures can be taken to reduce the exposure of these areas to coastal flooding. For example, in Singapore and Hong Kong, there are enforced minimum reclamation levels to account for future sea level rise
On the island of Kauai, Hawaii in the USA, the local governing county has implemented flexible and protective coastal setbacks that protect communities from coastal erosion and avoid shoreline armouring in the long term.
The aim of the Wallasea Island Wild Coast project is to recreate a natural intertidal coastal marshland to combat the threat of climate-induced coastal flooding. The recreated mudflats, salt and brackish marshes, saline lagoons, and pastures will provide a range of habitats for coastal birds and other wildlife on the Essex coast.
The Clacton to Holland-on-Sea (UK) stretch of coastline has suffered from significant sediment loss, which negatively impacts the local community and economy. Collectively, five kilometres of beach are at risk of washing away including nearby tourism promenades and over 3000 homes and businesses. In response, a major sea defence project is underway to fortify the coast through construction of new rock groynes and beach nourishment activities. It is expected that this project will reduce coastal erosion for the next 100 years.
The Ventura County Chapter of the Surfrider Foundation in California, USA decided against traditional coastal defence measures to reduce beach erosion at a popular beach spot called Surfer’s Point. Along with other stakeholders, the County instead designed a two-phase plan to strategically relocate a parking lot, pedestrian path, and bike path away from erosion zones.
Located on England’s North Norfolk coast, the Titchwell Marsh is a key piece of the North Norfolk Coast Special Protection Area (SPA) and Special Area of Conservation (SAC). This coastal wetland ecosystem includes freshwater and brackish habitats and is currently protected from the erosive power of waves by seawalls which are becoming increasingly weakened.
The Titchwell Marsh Coastal Change Project aims to protect vital freshwater habitats from both coastal erosion and sea level rise through managed realignment and seawall reinforcement, and mitigate and compensate for the loss of important brackish habitats.
In the face of increasing beach and dune erosion, the community of Quend-Plage, located on the Picardy coast of northern France, installed a beach drainage system in 2008. As a result of this, the macrotidal beach of Quend-Plage has been stabilized, preserving both natural habitats and recreational spaces.
The beach of Pevensey Bay (UK) is a shingle barrier beach under threat from flooding and coastal erosion. Today, the beach is managed in an adaptive manner developed by Pevensey Coastal Defence, where management activities respond to changes in risk and beach recharge and beach recycling is undertaken.
A construction of an elevated wooden pathway alongshore and cross-shore of about 1500 m, and the construction of a dune fences were implemented in the coastal town of Praia de Faro (Portugal). The fences helped to trap sand in the dune areas leading to a growth of the dune system. The wooden path played also an important role in the dune recovery.
Coral and oyster reefs are considered to be types of coastal wetlands. As a natural coastal defense they are a buffer for coastlines against waves. Reefs are threatened by rapid environmental change, making it very important to protect and restore reefs.
Coastal and marine environments are usually characterized by beautiful landscapes and rich ecosystems of great importance, offering elements such as rich biodiversity. They also attract human activities such as tourism and industrial uses. However, the co-existence of human activities and natural resources often creates conflicts of use in the coastal zone.
Management policies are an important means of implementing planning in order to minimise, prevent or resolve use conflicts. The development of a coastal and marine spatial planning system presents an opportunity for the implementation of an overall strategy of conservation, sustainability and management to maximise future economic profit.
The case study shows how sand replenishment at the west coast of Denmark has become the main measure to face coastal erosion. Experiences in the last years showed, that replenishments at the foreshore seem to be the most effective and ecosystem friendly version of beach nourishments.
This case study is about enhancing the natural dynamics of the dunes and the sand transport on the Wadden Sea island of Terschelling, Netherland
Flood forecasting is an essential tool for providing people still exposed to risk with advance notice of flooding, in an effort to save life and property.
To minimize the loss of lives and reduce other flood impacts, an area should be evacuated when the depth of standing water due to flooding is already or is expected to become high. Such floods are defined as those which are expected to cause buildings, including residential houses, to be washed away or seriously damaged by the flooding.
The purpose of early warning systems (EWS) is simple. They exist to give advance notice of an impending flood, allowing emergency plans to be put into action. EWS, when used appropriately, can save lives and reduce other adverse impacts.
It is vital to recognize that even after the implementation of non-structural flood mitigation measures residual flood risk will remain. It is of paramount importance to make plans to deal with flood events and their aftermath. This involves multiple activities which can be included as part of a flood emergency plan. In this section there is an overview of the elements central to emergency planning.
Flood risk awareness is the cornerstone of non-structural flood risk management. All actions to minimize the impact of flooding hinge upon stakeholders becoming aware these are both necessary and desirable. Ignorance of flood risk encourages occupation of the floodplain, in the first instance, and can allow appropriate building design practices to fall into disuse. In the event of a flood, the lack of awareness of risk can result in a failure to heed warnings to evacuate, thereby endangering lives.
In the RISC-KIT Case Study area of Emilia-Romagna (Italy), a study has been undertaken to gain insights about improvements of the design of beach scraping operations. Here, a numerical modeling approach was used to find more appropriate beach scraping design.
Managed realignment is a measure that usually results in the creation of a salt marsh by removing costal protection an allowing for an area previously protected from flooding to become flooded. Managed realignment is a measure dealing with sea level rise and coastal erosion. It is also often a method that replaces hard coastal defense measures with soft coastal landforms. Rather than relying on hard structures for defense, managed realignment depends on natural defenses to absorb or dissipate the force of waves.
Saltmarsh and mudflats are usually located together with mudflats in front of the saltmarsh. Saltmarsh vegetation and saltmarsh creeks help manage floods by dissipating wave and tidal energy. They are valuable barriers to the risks of flood, as they dissapte wave and tidal energy. Saltmarshes used in combination with other measures can have beneficial outcomes to managing climate change impacts. Even a small width of fronting saltmarsh can significantly reduce the height of sea walls required to achieve the same level of protection and thus also reduce initial construction costs. Having saltmarsh fronting will also significantly reduce maintenance costs due to the reduced exposure to wave and tidal energy.
A breakwater is a coastal structure (usually a rock and rubble mound structure) projecting into the sea that shelters vessels from waves and currents, prevents siltation of a navigation channel, protects a shore area or prevents thermal mixing (e.g. cooling water intakes). A breakwater typically comprises various stone layers and is typically armoured with large armour stone or concrete armour units (an exception are e.g. vertical (caisson) breakwaters). A breakwater can be built at the shoreline or offshore (detached or reef breakwater). This measure is not directly addressed to protect the coast in flood events, but can indirectly stabilize the coast by preventing erosion.
Beach drains comprise perforated land drain pipes buried below the upper beach surface, and connected to a pump and discharge. The concept is based on the principle that sand will tend to accrete if the beach surface is permeable due to an artificially lowered water table. The system is largely buried and therefore has no visual impact.
Dikes and dams need regular maintenance and strengthening to keep their protection capacities and meet safety requirements. In addition, climate scenarios for sea level rise and extreme weather conditions can lead to reconsidering safety requirements and building new protections on identified weak points or heightening and strengthening existing ones. The design of existing dikes and dams can be modified to fulfill different purposes.
A seawall or a revetment is a structure made of concrete, masonry or sheet piles, built parallel to the shore at the transition between the beach and the mainland or dune, to protect the inland area against wave action and prevent coastal erosion. Seawalls are usually massive structures designed to resist storm surges.
'Elevation of buildings' and ' Land raising' are two separated measures with the aim to elevate exposed elements.
Moving a building out of the existing flood hazard area is the safest solution among several retrofit-ting methods; however it is also usually the most expensive method (FEMA, 2009). When a community acquires a flood-prone home from the owner, relocation is often applied, as well as demolition of the building. The relocation is not only limited to buildings, it can also be applied to other exposed coastal infrastructure.
Coastal setbacks are an demarcated area where all or certain types of development are prohibited. Coastal setbacks can be measured either as a minimum distance from the shoreline for new buildings or infrastructure facilities, or may state a minimum elevation above sea level for development. Setbacks determined by distance from the shore are used to combat coastal erosion, while setbacks determined by evaluation are used to control flooding.
Sand dunes are wind forms elements on sandy coasts and represent a natural coastal protection measure. Natural processes like erosion and human interference (like coastal protection measures, changing coastal processes, tourism) can have a negative impact on dunes. Rehabilitation with feeding sand or planting vegetation can reinforce the dunes.
Highly dynamic coastal systems (like sandy beaches, dunes or estuaries) might be best managed by not interfering with the natural processes, but instead accepting that change will occur and adapting backshore management accordingly. Key in this approach is a proper monitoring of the processes to analyze and evaluate the changes (for examples at eroding cliffs or dunes). With a proper planning horizon, these changes can be anticipated and with enough room for the environment to involve this can be a very cost-extensive approach.
Artificial reefs are shore parallel rock mound structures set part way down the beach face. They may be long single structures or form a series of reefs extending for some distance alongshore. They are submerged for at least part of the tidal cycle, and are therefore less intrusive on the coastal landscape, have less impact on upper beach longshore processes and add a new intertidal habitat to sandy foreshores.
Groynes are cross-shore structures designed to reduce longshore transport on open beaches or to deflect nearshore currents within an estuary. On an open beach they are normally built as a series to influence a long section of shoreline that has been nourished or is managed by recycling. In an estuary they may be single structures.
A new form of beach nourishment is the 'Zandmotor' (sand-motor) undertaken in the Netherlands. Instead of having smaller nourishments in a time period of 4 to 5 years, the water authority Rijkswaterstaat formed 21.5 million m3 of sand into a peninsula near Ter Heijde in 2011. In the beginning, the peninsula stretched 1 km into the sea and was about 2km wide. The idea is that waves, current and wind spread the sand along the coast and thus enhance the coastal protection and at the same time create a dynamic natural and recreational area. It was expected to have a repeating interval of only 15-30 years.
Beach nourishment describes a measure where sediment that is lost due to longshore drift or erosion on a beach is replaced from material outside of the eroding beach. This results in a wider beach that can reduce storm damages and coastal erosion. Beach nourishment is typically a repetitive measure, since it does not remove the physical forces causing erosion, but is a measure that mitigates the effects of erosion.
Beach scraping is recovering material from the berm at the foreshore and placing it on the backshore at the foot of the dunes or the cliff.