Although there are many natural causes of coastal erosion, most of the causes affecting coastal communities are due to human intervention in the transport processes along the coastlines and/or reductions in the supply of sand to the shorelines. This article describes how all kind of human interventions may affect coastal erosion.
Coastal structures interfering with the littoral transport are the most common cause of coastal erosion. The presence of the structure has a series of effects:
Trapping of sand on the upstream side of the structure takes sand out of the sediment budget, thus causing shore erosion along adjacent shorelines. Mostly, of course, on the lee side, but large structures may also cause (initial) erosion on the upstream side.
- Loss of sand to deep water
Trapping of sand in entrance channels and outer harbours
The structures, which may cause this type of erosion, are:
- Groynes and similar structures perpendicular to the shore
- Inlet jetties at tidal inlets and river mouths detached breakwaters
The accumulation and erosion patterns adjacent to coastal structures depend among other things on:
- The type of coastline , i.e. the wave climate and the orientation of the shoreline
- The extent of the structure relative to the width of the surf-zone
- The detailed shape of the coastal structure