What are the 4 Coastal Erosion Processes?
Hydralic Action - occurs when waves striking a cliff face compress air in cracks on the cliff face. This exerts pressure on the surrounding rock, and can progressively splinter and remove pieces of rock. Over time, the cliff face cracks can grow, sometimes forming a cave.
Attrition - occurs when waves causes loose pieces of rock debris (scree) to collide with each other. The effect is that pieces of scree collide, grinding and chipping each other, progressively becoming smaller, smoother and rounder. Scree also collides with the base of the cliff face, and can chip small pieces of rock from the cliff or have a corrasion (abrasion) effect, similar to sandpapering.
Abrasion - occurs when the waves break on the cliff face pounding the cliff face and slowly erode it. As the sea pounds cliff faces it also uses the scree from other wave actions to batter and break off pieces of rock from higher up the cliff face which can be used for this same wave action and to attrition.
Corrosion – or solution occurs when the sea's pH (anything below pH 7.0) corrodes rocks on a cliff face. Limestone cliff faces, which have a high pH, are particularly affected in this way.
Groynes are wooden often made of greenhart, concrete and/or rock barriers or walls perpendicular to the sea. Beach material builds up on the updrift side, where littoral drift is predominantly in one direction, creating a wider and a more plentiful beach, therefore enhancing the protection for the coast because the sand material filters and absorbs the wave energy. However, there is a corresponding loss of beach material on the downdrift side, requiring that another groyne to be built there. Moreover, groynes do not protect the beach against storm-driven waves and if placed too close together will create currents, which will carry sand material offshore.
Groynes are extremely cost-effective coastal defense measures, requiring little maintenance, and are one of the most common coastal defense structures. However, groynes are increasingly viewed as detrimental to the aesthetics of the coastline, and face strong opposition in many coastal communities.
Many experts consider groynes to be a "soft" solution to coastal erosion because of the enhancement of the existing beach.
In addition to being costly, there is also a problem called Terminal Groyne Syndrome. The last groyne that has been built or the terminal groyne, prevents longshore drift from bringing material to other nearby places. This is a common problem along the Hampshire and Sussex coastline in the UK; a perfect example is Worthing.