Coastal Protection - Approaches to Shoreline Management

The systems perspective has led to the use of sediment cells on which to base coastal management planning.

Around the coast of England and Wales there exist 11 sediment cells: largely self-contained sediment systems around which sediment is recycled. Usually bounded by a key physical demarcation feature, such as a major headland or river estuary, sediment cells are subdivided into sub-cells where the coastline is more uniform for short section (a section of rocky cliff before it changes to softer glacial till).

Local authorities and other bodies responsible for shoreline management develop plans for coastal intervention, or otherwise, that have key targets for 20, 50 and 100 years’ time.

Their four key options for shoreline management are:

Hold the line: intervene against coastal erosion with hard or soft engineering to prevent any further shoreline retreat.

Managed retreat: realignment of the coast to a pre-determined line some distance further inland from the current position of the coast (see above)

Advance the line: extend the coast into what is currently the sea. (Very few examples around Britain, but the basis of Dutch polder reclamation and construction of man-made islands in Tokyo Bay).

No active intervention: permit natural systems to modify the coastline as they are currently operating. It usually means allowing erosion and cliff retreat to continue.

The factors that determine which of the four options is designated for a section of coast depends on

• The rate of coastal change (threatened loss of land as well as sea level rise)
• The economic value of land uses put at risk by coastal change (homes, businesses, infrastructure)
• The value of agricultural land at risk, along with habitats of value
• The cost of intervention strategies

Issues can arise if one section of coast is selected for ‘Hold the line’ strategies but a neighbouring section is designated ‘No active intervention’ without clear justification. Even more controversial is when the ‘Hold the line’ strategy selected actually increases the rate of coastal erosion downcoast (such as with sediment-capture by groynes).