Coastline management strategies

Coastlines are attractive spaces subject to a high population pressure. In UK, 36% of the people lived within 5 km from the sea and 94% within 50 km (in 2006).

They are varied territories with very different environments (beaches, cliffs, dunes, estuaries, etc.) and which are given over to a variety of uses (commercial and industrial activities; commercial and fishing ports, marinas; water sports, etc.). Also, thanks to their diversity, coastlines attract high numbers of tourists. For example, the town of Biarritz, in France, grows from 23 000 to 110 000 inhabitants during the summer season.

Nowadays, with the increasing frequency of marine weather phenomena such as storms and the population growth in coastal areas, communities are rethinking the way in which coastlines are developed.

Consequently, several strategies have been put in place in order to protect stakes on the European coast. There are four types of strategies: engineering solutions, the adaptation or support of natural processes, relocation or strategic retreat and passive monitoring.

Depending on the stakes to be protected (homes, infrastructure, natural habitats, etc.) different strategies will be favoured.

Traditionally, coastal erosion is tackled by "hard" defensive structures designed to withstand the onslaught of the sea (groynes, walls, breakwaters, etc.). These techniques can often prevent local erosion but contribute to erosion in an area near the protected zone.

In order to resolve these problems, other "soft" protection systems are being developed and offer the advantage of blending better into the natural landscape and having less of an impact on biodiversity.

1. Hard engineering methods (seawalls, groynes, riprap, etc.)

These techniques are based on two different principles:

-    structures perpendicular to the coast, such as groynes, help notably to minimise the transport of sand by longshore currents (longshore drift). The beaches are replenished with sand and wave energy is dissipated.

Groyne in Westende-Bad, Belgium © Filip Bunkens / Unsplash

-    structures parallel to the coast (seawalls, breakwaters, riprap, etc.) create an obstacle to the waves and stabilise the coastline.

Breakwater in Holyhead, Wales, United Kingdom © Jean Mottershead / Flickr (Creative Commons)

Disadvantages:

-    Huge impact both on the landscape and on biodiversity

-    Very expensive

-    Partial or total disruption of leisure activities such as surfing

-    Greater erosion further along the coastline (which means simply relocating the problem)

Greater erosion further along the coastline © Surfrider Foundation Europe

2. Soft engineering methods (beach nourishment, geotextile)

This strategy to combat the advance of the sea aims to dissipate wave energy and minimise changes to the ecosystem.

These techniques help to keep a dry beach at high tide, unlike the hard engineering methods. The impact on the landscape and the cost of these ‘soft’ methods are considerably lower too. Another advantage of the soft approach is that most leisure activities on the coast are not disrupted.

Beach nourishment by boat © City of Gold Coast  

Beach nourishment by bulldozer © DutchWaterSector

Geotextile tubes © GlobalSynthetics

Disadvantages:

-    Less sustainable and efficient over time

-    Requires regular maintenance

-    Beach replenishment has an impact on biodiversity

-    Risk of a lack of sand (example of Lacanau, in France: for 1.2 km of coastline, the annual requirement for sand is estimated to be 72 000 m3)

Dunes and wetlands naturally protect the coastline. Their rehabilitation or reinforcement can slow down the phenomenon of erosion and thereby reduce the risk of flooding.

1. Dune rehabilitation

For dune rehabilitation, the natural processes are supported by the installation of wooden barriers (sand fences) and the planting of vegetation which traps the sand. This prevents the sand, carried by the wind, from advancing inland. The dune is stabilised and can even gain land on the sea.

This process is slow and requires patience and specific measures to prevent people walking over the protected areas. This forces users to make detours to access the beach, but this small effort is rewarded in the long term thanks to the preservation of a healthy beach enabling users to enjoy their coastal activities.

Sand Dune restoration work in progress at Spencer Park Beach, Christchurch, New Zealand © Emma Kelland / Wikipedia (Creative Commons)

Disadvantages:

-    Requires regular maintenance of the dunes and installation of essential protective structures

-    Slows down the erosion process but does not stop it

-    Only suitable for zones where a large dune system already exists

2. Rehabilitation of wetlands

Many wetlands on the French coastline have been dried out over recent centuries to make way for farmland or building land, to fight against the invasion of mosquitoes (the Landes forest, for example) or to facilitate access to the coast. Yet these areas act as “buffer” zones which can absorb significant quantities of water and which are capable of slowing down waves during storms. They thereby considerably reduce the risk of flooding and re-establish biodiversity.

Apart from its capacity to protect the coast, the rehabilitation of wetlands would favour the development of leisure activities such as fishing, nature observation, walks, etc. That can be a real advantage for a territory and its inhabitants, improving the living environment in keeping with a sustainable development approach.

Newtown National Nature Reserve, Isle of Wight © Wightlink

Disadvantages:

-    Large areas of coastline need to be left in a natural state

-    Tourist development limited to “green tourism”

Relocation involves demolishing and moving seafront properties and activities inland. This solution is envisaged when maintaining the coastline becomes technically impossible or when the cost of doing so becomes too high.

In areas where the coastline is retreating fast, relocation can be envisaged when few properties are concerned and they can be easily moved (for example: a campsite).

Skipsea Sands caravan park, United Kingdom © internetgeography.net

This strategy requires accurate forecasting on the part of local authorities and a vast programme of information and communication to convince stakeholders (inhabitants and businesses). While it seems to be the only long-term solution faced with the growing risk of erosion in certain areas, it is very complex to put in place, notably due to the thorny issue regarding the compensation of the people concerned as it can be difficult to find the necessary funding.

Disadvantages:

-    Numerous regulatory, operational and financial obstacles to overcome

-    Very slow to put in place, which often involves finding an expensive temporary protection solution

-    A feasibility study needs to be carried out beforehand involving all local stakeholders

-    Low social acceptability (difficult to convince the people concerned)

This involves letting nature take its course, without human intervention. The ecosystem is often able to regain normal functioning after having suffered an external disturbance (a storm for example). This is known as "resilience".

These natural areas are nevertheless monitored by the relevant bodies which study their evolution in order to anticipate any change.

Although relatively inexpensive, this solution is unfortunately suitable for very few places. These areas are shrinking as a result of tourism development and population growth.

For example, the designation of Natura 2000 protected areas is a measure which help to preserve untouched spaces which can thereby act as buffer zones.

Northumberland Coast, England, classified as "Area of Outstanding Natural Beauty"

© George / SkyPixel

Disadvantages:

-    Few areas are concerned

-    Requires in-depth knowledge of the territories

Often, local authorities apply several strategies to their territory, depending on the configuration of their coasts, the budget and the stakes to protect. These are difficult decisions to take and consultation among stakeholders (decision makers, managers, users, inhabitants, business owners, etc.) is essential.

Coastline: the line that forms a boundary between the land and the sea. It is sometimes difficult to define on a coast in constant movement such as a sandy coast. We define it as such:

                 Sandy coast = boundary formed by the foot of the dune 

                 Rocky coast = boundary formed by the top of the cliff.

Sand fence: barrier formed by assembling vertical wooden slats separated from each other by a space the width of which determines the permeability of the barrier.