Question

Describe what groins, sea walls, and beach nourishment are and what each does to the shorefront overtime..

Answer 1

The words mentioned here like groins, seawalls and beach nourishment are all protection structures constructed to protect the beaches. But the nature of protection of each is different in it's own way.

Groins = These are structures that are used to protect beaches from erosion. These structures are constructed perpendicular to the shore, leaving beach behind them, thus helping to control the amount of sand going towards the shore. Usually the longshore drift current approaches the beach and when they go back ,they take a lot of sand along with them, thus eroding the beach. In order to prevent this erosion we construct groins, thus the erosion is said to be stopped. But it actually isn't. Because, when the longshore drift current approaches the groin, which is a very hard structure usually built if concrete, steel or wood, the drift current is forced to slow down and thus the sand is deposited on one side of the groin, but on the expense of the other side. Thus erosion does occur at the other side of the groin, but not that harmful. A groin is just helping shift the erosion from one side of the beach to the other side.Even though groins are told to be beach saving structures, it is obviously not natural and will affect the natural balance of the waves, will affect swimmers, surfers etc and at the end, since the amount of sand in the beach has no change with the arrival of groin, it's as that no matter as many groins you construct to protect the beach from erosion, there will be sand erosion at the other side of the last groin.

Sea walls = Sea walls are also constructed to prevent erosion. But unlike groins, seawalls are parallel structures facing the beach and they are also made of concrete, steel, boulders etc. What a sea wall does is that, it reduces the effect of erosion caused by the waves by reflecting back the wave energy to the sea itself,thus making available only less energy for the waves. But even though a seawall is good to reduce the impact of tsunamis etc, but the reflected wave energy will eventually lead to disappearance of beach because the backlash takes beach sand along with it. Another drawback of a seawall is that, it's existence will lead to over erosion of the adjacent areas those donot have their own seawall. Thus it is recommended not to construct a seawall but if it's inevitable, then try to make its face sloped to the sea,or else try natural barrier methods like growing mangroves, coastal vegetation like coconut plantations seen in India, etc can be adopted. But still as a long term solution, ignoring the negatives seawalls are undoubtedly the best coastal defence ever.

Beach nourishment = This is also a coastal defence mechanism, but nothing is constructed in this case. We just replace the lost sand in the beach using some other sources. It's simply depositing sand so as  to widen or strengthen the beach. This is considered a better approach nowadays because of zero construction of structures. Still this can take a little while to be completely accepted by the ecosystem because it's not necessary that the size of sand deposited and the size of beach sand must be similar. This will lead to the fast erosion of the nourished beach as compared to the previous beach and can bury the marine organisms which is a serious impact. .but still, this method protects the structures behind the beach to some extent.