The coastal zone is a dynamic area of ​​natural changes and increasing human use. Although it occupies less than 15% of the Earth's surface, it is home to more than 50% of the world's population (it is estimated that more than 3.1 billion people live less than 200 kilometers from the sea). Given that three-quarters of the world's population is expected to reside in the coastal zone by 2025, human activities originating in this small portion of territory will impose exorbitant pressure on the global system. Coastal areas contain rich resources to produce goods and services in addition to hosting most commercial and industrial activities. In the European Union, almost half of the current population lives less than 50 kilometers from the sea and the resources of coastal areas produce much of its economic wealth. Fishing, shipping and tourism compete for living space along the estimated 89,000 kilometers of coastline, and coastal areas contain some of the most valuable and fragile natural habitats in Europe. Until the 1950s, coastal protection consisted of the interposition of static structures between the sea and the land to prevent erosion and/or flooding, having a long tradition. For this period, new techniques or friendly policies have been developed to preserve the environment when this is possible. They continue to be important when it comes to low-lying areas that require protection.[4]​ For example: Venice, New Orleans, Holland or the Caspian Sea.

Protection against sea level rise in the century will become especially important as sea level rise is accelerating today. This will represent a challenge for coastal management, as sea walls and breakwaters are generally expensive to build, so the costs of building protection to combat rising sea levels can be enormous.

Changes in sea level cause direct adaptive responses of beaches and coastal systems, as we can see in the succession of a drop in sea level. When sea level rises, coastal sediments are partially moved upward by waves and tidal energy, so that the process of sea level rise has a component of landward sediment transport. This leads to a dynamic model of the effects of rise with continuous displacements of sediments that is not compatible with static models where changes in the coastline are based solely on topographic data.

Existen cinco estrategias genéricas[1] para la defensa costera:.

La decisión de qué estrategia adoptar corresponde a cada lugar específico, en función del patrón de cambio relativo del nivel del mar, las condiciones geomorfológicas, la disponibilidad de sedimentos y la erosión, a lo que hay que añadir una serie de factores sociales, económicos y políticos.

De forma alternativa, se pueden emplear enfoques de la gestión integrada en áreas litorales para prevenir el desarrollo en las zonas propensas a la erosión o a las inundaciones. La gestión del crecimiento") puede representar un reto para las autoridades locales costeras quienes a menudo se las ven y se las desean para proveer las infraestructuras necesarias para las nuevas personas residentes que vienen buscando nuevas formas de vida en la costa.[5]​ Las inversiones en transporte sostenible para reducir el promedio de la huella ecológica de las personas visitantes de las costas son a menudo una buena manera de salir del atasco costero. Algunos ejemplos son Dongtan y la vía oceánica de la Costa Dorada de Queensland, Australia.

do nothing

The 'do nothing' option, which means not protecting, is a cheap and convenient way to let the coast take care of itself. It involves the abandonment of coastal infrastructure when exposed to coastal erosion, and a gradual retreat inland or evacuation and relocation somewhere else. This option is environmentally friendly and the only pollution it produces is during the resettlement process. However, it means the loss of many lands to the sea and people losing their houses and homes.

Manage recoil

Managing setback is an alternative to building or maintaining coastal structures. The controlled retreat allows areas that were not previously exposed to flooding from the sea to become flooded. This process occurs in low estuarine or deltaic areas and almost always involves the flooding of lands that at some point in the past had been claimed by the sea. Controlled retreat often represents a response to changes in the sedimentary balance or rises in sea level. This technique is used when the land adjacent to the sea is of little value. This decision is made to allow the land to erode and flood, creating new marine, intertidal and marsh habitats. This process can continue for many years leading to natural stabilization.

The first controlled retreat in the UK was in an area of 0.8 ha on Northey Island in Essex, following the floods of 1991. This was followed by Tollesbury and Orplands, also in Essex, where sea walls were breached in 1995. In the Ebro Delta (Spain) coastal authorities are planning controlled retreat in response to coastal erosion (MMA 2005, Sitges, Meeting on Coastal Engineering; EUROSION project).

Cost - The main cost is usually the purchase of the land to be flooded. Compensation may be necessary for the relocation of resident persons. Any other anthropogenic structure that is going to be engulfed by the sea must be properly dismantled to prevent marine pollution. In some cases, a retaining wall must be built to protect land beyond the area to be flooded, although these structures are generally lower than those that would be necessary to protect the existing shoreline. Monitoring the evolution of the flooded area represents an additional cost. Costs can be reduced by allowing existing defenses to fail naturally, but often coastal realignment projects will be managed more actively, for example by creating artificial cracks in existing defenses to allow the sea in at a given location and in a predetermined manner, or by preparing pre-drainage channels for the creation of mudflats.

Maintain current line

Human strategies on the coast have been largely based on static engineering responses, while the coast is in dynamic equilibrium, or strives to be so. Strong coastal structures continue to be built because they protect expensive property and infrastructure, but they usually shift the problem downstream or to other parts of the coast. Soft solutions such as beach regenerations seem more acceptable even though they are temporary and require periodic replenishment, and in some way restore the natural dynamism of the coastline. Even so, in many cases there is a legacy of decisions that were made in the past that bring to light many of the threats to coastal infrastructure in the present and that need immediate protection. For example, the jetty and promenade of many coastal cities in Europe represents a highly intervened use of primary waterfront space, which could preferably be designated as public open space, park and amenities, if available now. Such open spaces could also provide great flexibility in terms of future land use changes, for example in the face of controlled retreat, addressing threats of erosion or flooding resulting from sea level rise. Dune areas represent natural reserves available in the event of extreme events, construction in these areas leaves little option except to take costly protective measures against the threat of such extreme events (no matter whether amplified or not by gradual global change). Controlled setback may include batteries of measures, such as progressive easements and other planning tools, including construction tools based on certain designed durability. The maintenance of these structures or soft techniques can reach a critical point (environmental or economic) that leads to changing the adoption of the strategy.

Move towards the sea

The futility of trying to predict future scenarios when there are great human influences is evident. Even the future climate is to some extent a function of what humans decide to do with it, for example reducing greenhouse gas emissions to control climate change. In some cases - where new areas are needed for new ecological or economic development - a strategy of moving towards the sea can be adopted. Some examples taken from EUROSION are: Koge Bay (Denmark), the western Scheldt estuary (Holland), Châtelaillon-Plage (France) and the Ebro delta (Spain).[2].

There is an obvious drawback to this strategy. Coastal erosion is widespread today and there are many coasts where exceptionally high tides or storm surges lead to shoreline encroachments, affecting human activity. If the sea rises, many coastlines that have developed infrastructure along or near the coastline will be unable to adapt to erosion, and will experience what is called "shoreline narrowing." This occurs when ecological or geomorphological areas that would normally be retreated inland encounter solid structures that prevent this. Marshes, mangroves, and adjacent coastal or freshwater wetlands are particularly prone to this narrowing.

Limited intervention

Limited interventions are actions taken when problem management only resolves it to a certain extent, usually in areas of little economic relevance. Limited intervention measures often involve encouraging succession of mudflats and sand dunes. This usually ensures that the land behind the marsh is sufficiently protected, since the wave energy will be dissipated by the accumulated sediment and by the new vegetation resident in the newly formed habitat. Although the new marsh is not strictly attributable to humans, as many natural processes will contribute to marsh succession, anthropogenic factors are partially responsible for its formation as an initial push may be necessary to help begin the succession process.

Lo que sigue es un catálogo de técnicas relevantes que pueden ser empleadas como técnicas de gestión costera. Los costes son estimaciones groseras realizadas durante 2005, basadas en libras esterlinas..

Hard construction techniques

Groynes are barriers or walls perpendicular to the sea made of wood, cement and/or rocks. Beach materials accumulate where the longshore drift current is predominantly in one direction, creating a wider, more developed beach, and therefore improving shoreline protection because the sandy material filters and absorbs wave energy. However, there is a corresponding loss of sandy material downstream of the drift stream, so another groyne has to be built there. Furthermore, groynes do not protect the beach against storm waves and if they are placed too close together they create currents that carry the sandy material away from the coast.

Groynes are extremely cost-effective coastal defense measures, requiring little maintenance, and are one of the most widespread coastal defense structures. However, they are increasingly seen as detrimental to the aesthetics of the coastline and encounter strong opposition in many coastal communities.

Many experts consider groynes as a "soft" solution given the improvement of the existing beach.

The estimated cost is £200,000 per groyne, about £60 per metre.

In addition to its high cost, there is a problem called Terminal Groyne Syndrome. The last groyne to be built, or terminal groyne, prevents coastal drift from providing materials from nearby locations. This is a very common problem on the British coasts of Hampshire and Sussex.

Walls, usually made of masonry, concrete or rock, are built at the base of cliffs or to protect settlements from erosion or flooding. The old-style walls reflect all the energy of the waves back to the sea, and to this end the walls were often finished in a warped shape, which also increases local turbulence, resuspending sand and sediment during storms.

Modern walls attempt to destroy most of the incident energy, resulting in fewer reflected waves and reduced turbulence, by taking the form of sloped cladding. Current designs are made with porous forms of rocks and concrete elements (Seabees, SHEDs,

Care must be taken in the choice of location for the wall, particularly in relation to the prism swept across the beach profile, the consequences of long-term beach recessions, and with respect to the level of service crest. These factors must be taken into account when evaluating the relationship between cost and benefit, which must be favorable for the construction of the wall to be justified.

Walls can make beaches dissipative, rendering them useless for their purposes. Their presence can leave a scar on the landscape they are trying to save.

Some modern examples are Cronulla (NSW, 1985-6),[6]​ Blackpool (1986-2001),[7]​ Lincolnshire (1992-1997)[8]​ and Wallasey (1983-1993). The Blackpool and Cronulla sites can both be visited using Google Earth and local webcams (Cronulla, Cleveleys).

A more interesting example is the wall at Sandwich Kent, where a "Seabee" wall is buried back from the beach under the shingle with the crown level at the level of the road kerb.

Walls are probably the second most traditional method used in coastal management.

The estimated cost is between £800 and £5,000 per linear metre.

The coastal zone is a dynamic area of ​​natural changes and increasing human use. Although it occupies less than 15% of the Earth's surface, it is home to more than 50% of the world's population (it is estimated that more than 3.1 billion people live less than 200 kilometers from the sea). Given that three-quarters of the world's population is expected to reside in the coastal zone by 2025, human activities originating in this small portion of territory will impose exorbitant pressure on the global system. Coastal areas contain rich resources to produce goods and services in addition to hosting most commercial and industrial activities. In the European Union, almost half of the current population lives less than 50 kilometers from the sea and the resources of coastal areas produce much of its economic wealth. Fishing, shipping and tourism compete for living space along the estimated 89,000 kilometers of coastline, and coastal areas contain some of the most valuable and fragile natural habitats in Europe. Until the 1950s, coastal protection consisted of the interposition of static structures between the sea and the land to prevent erosion and/or flooding, having a long tradition. For this period, new techniques or friendly policies have been developed to preserve the environment when this is possible. They continue to be important when it comes to low-lying areas that require protection.[4]​ For example: Venice, New Orleans, Holland or the Caspian Sea.

Protection against sea level rise in the century will become especially important as sea level rise is accelerating today. This will represent a challenge for coastal management, as sea walls and breakwaters are generally expensive to build, so the costs of building protection to combat rising sea levels can be enormous.

Changes in sea level cause direct adaptive responses of beaches and coastal systems, as we can see in the succession of a drop in sea level. When sea level rises, coastal sediments are partially moved upward by waves and tidal energy, so that the process of sea level rise has a component of landward sediment transport. This leads to a dynamic model of the effects of rise with continuous displacements of sediments that is not compatible with static models where changes in the coastline are based solely on topographic data.

Existen cinco estrategias genéricas[1] para la defensa costera:.

La decisión de qué estrategia adoptar corresponde a cada lugar específico, en función del patrón de cambio relativo del nivel del mar, las condiciones geomorfológicas, la disponibilidad de sedimentos y la erosión, a lo que hay que añadir una serie de factores sociales, económicos y políticos.

De forma alternativa, se pueden emplear enfoques de la gestión integrada en áreas litorales para prevenir el desarrollo en las zonas propensas a la erosión o a las inundaciones. La gestión del crecimiento") puede representar un reto para las autoridades locales costeras quienes a menudo se las ven y se las desean para proveer las infraestructuras necesarias para las nuevas personas residentes que vienen buscando nuevas formas de vida en la costa.[5]​ Las inversiones en transporte sostenible para reducir el promedio de la huella ecológica de las personas visitantes de las costas son a menudo una buena manera de salir del atasco costero. Algunos ejemplos son Dongtan y la vía oceánica de la Costa Dorada de Queensland, Australia.

do nothing

The 'do nothing' option, which means not protecting, is a cheap and convenient way to let the coast take care of itself. It involves the abandonment of coastal infrastructure when exposed to coastal erosion, and a gradual retreat inland or evacuation and relocation somewhere else. This option is environmentally friendly and the only pollution it produces is during the resettlement process. However, it means the loss of many lands to the sea and people losing their houses and homes.

Manage recoil

Managing setback is an alternative to building or maintaining coastal structures. The controlled retreat allows areas that were not previously exposed to flooding from the sea to become flooded. This process occurs in low estuarine or deltaic areas and almost always involves the flooding of lands that at some point in the past had been claimed by the sea. Controlled retreat often represents a response to changes in the sedimentary balance or rises in sea level. This technique is used when the land adjacent to the sea is of little value. This decision is made to allow the land to erode and flood, creating new marine, intertidal and marsh habitats. This process can continue for many years leading to natural stabilization.

The first controlled retreat in the UK was in an area of 0.8 ha on Northey Island in Essex, following the floods of 1991. This was followed by Tollesbury and Orplands, also in Essex, where sea walls were breached in 1995. In the Ebro Delta (Spain) coastal authorities are planning controlled retreat in response to coastal erosion (MMA 2005, Sitges, Meeting on Coastal Engineering; EUROSION project).

Cost - The main cost is usually the purchase of the land to be flooded. Compensation may be necessary for the relocation of resident persons. Any other anthropogenic structure that is going to be engulfed by the sea must be properly dismantled to prevent marine pollution. In some cases, a retaining wall must be built to protect land beyond the area to be flooded, although these structures are generally lower than those that would be necessary to protect the existing shoreline. Monitoring the evolution of the flooded area represents an additional cost. Costs can be reduced by allowing existing defenses to fail naturally, but often coastal realignment projects will be managed more actively, for example by creating artificial cracks in existing defenses to allow the sea in at a given location and in a predetermined manner, or by preparing pre-drainage channels for the creation of mudflats.

Maintain current line

Human strategies on the coast have been largely based on static engineering responses, while the coast is in dynamic equilibrium, or strives to be so. Strong coastal structures continue to be built because they protect expensive property and infrastructure, but they usually shift the problem downstream or to other parts of the coast. Soft solutions such as beach regenerations seem more acceptable even though they are temporary and require periodic replenishment, and in some way restore the natural dynamism of the coastline. Even so, in many cases there is a legacy of decisions that were made in the past that bring to light many of the threats to coastal infrastructure in the present and that need immediate protection. For example, the jetty and promenade of many coastal cities in Europe represents a highly intervened use of primary waterfront space, which could preferably be designated as public open space, park and amenities, if available now. Such open spaces could also provide great flexibility in terms of future land use changes, for example in the face of controlled retreat, addressing threats of erosion or flooding resulting from sea level rise. Dune areas represent natural reserves available in the event of extreme events, construction in these areas leaves little option except to take costly protective measures against the threat of such extreme events (no matter whether amplified or not by gradual global change). Controlled setback may include batteries of measures, such as progressive easements and other planning tools, including construction tools based on certain designed durability. The maintenance of these structures or soft techniques can reach a critical point (environmental or economic) that leads to changing the adoption of the strategy.

Move towards the sea

The futility of trying to predict future scenarios when there are great human influences is evident. Even the future climate is to some extent a function of what humans decide to do with it, for example reducing greenhouse gas emissions to control climate change. In some cases - where new areas are needed for new ecological or economic development - a strategy of moving towards the sea can be adopted. Some examples taken from EUROSION are: Koge Bay (Denmark), the western Scheldt estuary (Holland), Châtelaillon-Plage (France) and the Ebro delta (Spain).[2].

There is an obvious drawback to this strategy. Coastal erosion is widespread today and there are many coasts where exceptionally high tides or storm surges lead to shoreline encroachments, affecting human activity. If the sea rises, many coastlines that have developed infrastructure along or near the coastline will be unable to adapt to erosion, and will experience what is called "shoreline narrowing." This occurs when ecological or geomorphological areas that would normally be retreated inland encounter solid structures that prevent this. Marshes, mangroves, and adjacent coastal or freshwater wetlands are particularly prone to this narrowing.

Limited intervention

Limited interventions are actions taken when problem management only resolves it to a certain extent, usually in areas of little economic relevance. Limited intervention measures often involve encouraging succession of mudflats and sand dunes. This usually ensures that the land behind the marsh is sufficiently protected, since the wave energy will be dissipated by the accumulated sediment and by the new vegetation resident in the newly formed habitat. Although the new marsh is not strictly attributable to humans, as many natural processes will contribute to marsh succession, anthropogenic factors are partially responsible for its formation as an initial push may be necessary to help begin the succession process.

Lo que sigue es un catálogo de técnicas relevantes que pueden ser empleadas como técnicas de gestión costera. Los costes son estimaciones groseras realizadas durante 2005, basadas en libras esterlinas..

Hard construction techniques

Groynes are barriers or walls perpendicular to the sea made of wood, cement and/or rocks. Beach materials accumulate where the longshore drift current is predominantly in one direction, creating a wider, more developed beach, and therefore improving shoreline protection because the sandy material filters and absorbs wave energy. However, there is a corresponding loss of sandy material downstream of the drift stream, so another groyne has to be built there. Furthermore, groynes do not protect the beach against storm waves and if they are placed too close together they create currents that carry the sandy material away from the coast.

Groynes are extremely cost-effective coastal defense measures, requiring little maintenance, and are one of the most widespread coastal defense structures. However, they are increasingly seen as detrimental to the aesthetics of the coastline and encounter strong opposition in many coastal communities.

Many experts consider groynes as a "soft" solution given the improvement of the existing beach.

The estimated cost is £200,000 per groyne, about £60 per metre.

In addition to its high cost, there is a problem called Terminal Groyne Syndrome. The last groyne to be built, or terminal groyne, prevents coastal drift from providing materials from nearby locations. This is a very common problem on the British coasts of Hampshire and Sussex.

Walls, usually made of masonry, concrete or rock, are built at the base of cliffs or to protect settlements from erosion or flooding. The old-style walls reflect all the energy of the waves back to the sea, and to this end the walls were often finished in a warped shape, which also increases local turbulence, resuspending sand and sediment during storms.

Modern walls attempt to destroy most of the incident energy, resulting in fewer reflected waves and reduced turbulence, by taking the form of sloped cladding. Current designs are made with porous forms of rocks and concrete elements (Seabees, SHEDs,

Care must be taken in the choice of location for the wall, particularly in relation to the prism swept across the beach profile, the consequences of long-term beach recessions, and with respect to the level of service crest. These factors must be taken into account when evaluating the relationship between cost and benefit, which must be favorable for the construction of the wall to be justified.

Walls can make beaches dissipative, rendering them useless for their purposes. Their presence can leave a scar on the landscape they are trying to save.

Some modern examples are Cronulla (NSW, 1985-6),[6]​ Blackpool (1986-2001),[7]​ Lincolnshire (1992-1997)[8]​ and Wallasey (1983-1993). The Blackpool and Cronulla sites can both be visited using Google Earth and local webcams (Cronulla, Cleveleys).

A more interesting example is the wall at Sandwich Kent, where a "Seabee" wall is buried back from the beach under the shingle with the crown level at the level of the road kerb.

Walls are probably the second most traditional method used in coastal management.

The estimated cost is between £800 and £5,000 per linear metre.