Movement Of Sediment Down The East Coast example essay topic

Human activities add another layer of complexity to the natural processes of coastal lands and materials. These activities may have direct or indirect effects on our changing coastlines. They may effect sources of new sediment to the coast and the movement of sediment within the coastal environment. Sediment starvation caused by river and coastal management is one effect of human activities on the coast. For some coastal regions, such as the Pacific coast, a large part of their sediment is supplied by rivers. Dams built for flood control and water catchment along the rivers leading to these coasts inhibit the transport of large grained sediment, The coasts lack new material so erode and move inland.

For instance damming of the tributary rivers to the Mississippi River over the past 60 years has reduced the movement of sediment. Studies in recent years have demonstrated that the amount of sediment carried by the Mississippi has been cut in half, aggravating the deterioration of Louisianas wetlands. An important source of sediment to Louisianas delta wetlands was periodic flooding of the Mississippi River, which deposits new material on the flood plain. Massive levees built along the river bans now contain these floods and eliminate the supply of sediment to the wetlands. As a results, the natural compaction and subsidence of the delta are no longer balanced by the deposition of new sediments, and the local relative sea level is rising as much as 1 cm per year. Human actions can also lead to the destruction of dune grasses and the disturbance of coastal landforms promotes increased erosion and movement of beach materials.

Human leisure activities such as rambling, horseracing and using off road vehicles on sand dunes, compact the sand, destroying plant roots and animal burrows. This leaves the sand dunes more susceptible to erosion causing blowouts and disrupting the succession of vegetation in the area. This has been a problem at Stud land Bay in Dorset on the south coast of England. Persistent human leisure activities on the dunes has led to substantial erosion in some parts of these dunes which has meant that Management programs have had to been introduced by English Nature. Sand dunes help absorb the pounding of high waves and reduce over wash flooding in storms. It has become common for sand dunes to be bulldozed to improve the views to the sea.

However this destroys the natural protection of the coast. Human activities such as water transport also can cause problems for coastal areas. The dredging of navigation channels and the discharging of the material in deep water to enable larger ships to travel though water channels removes sediment from the coastal system leaving the area susceptible to erosion and will also interfere with longshore drift which will prevent the coastal beach landforms from being maintained such as the development of a spit. It is likely that a spit will be eroded and start to regress in conditions such as these.

An example is Spurn head Spit. Spurn head is located, on the humber Estuary in North East England. The growth and destruction of Spurn head occurs on a regular cycle of about 250 years. It is likely that human activity has increased the amount of erosion at Spurn head.

In the 18th and 19th Centuries, Whalers used shingle from spurn head as ballast. At its peak 500 000 tonnes per year were removed. This hastened the destruction of the ridge shingle beaches that protected the sandy beaches beneath. Shingle beaches were able to withstand the force of the strong gales whereas sandy beaches could not, leading to erosion of the spit.

Because sediment was being removed, the spit was not able to grow again as it was destroyed. Sea defences further restricted movement of sediment down the East Coast. In the 1830's and 1840's severe storms breached the neck of the spit causing flooding to the surrounding area. The lack of sediment is also threatening to erode the mudflats behind the head.

Industry is another human activity that can interfere with coastal landforms. More the proposed port development at Dibden Bay has caused controversy because of the impacts it may have on the coastal environment. Dibden Bay is 240 hectare of open grazing marsh and mudflats situated on the western shores of Southampton water opposite, Southampton's existing port. The area forms part of an internationally important wildlife area.

However, Associated British Ports (ABP) propose to build a container terminal on this land. It will service new ships carrying up to 7000 containers. However, if this proposal is to go ahead, it will lead to the total loss of the foreshore mudflats and grazing marsh. There will also need to be dredging of the channel, which will cause coastal erosion, redistribution of sediments and variation of the channels usual flow. The main problem with human activity and the coasts is that human activities often conducted without an adequate understanding of coastal geology and process. The effects of damming the Mississippi is a good example.

So that even human activities intended to save or improve the coast may inadvertently cause erosion. More investigations need to be carried out on proposed developments such as Dibden Port and the effect it will have on the coast before they are allowed to be carried out to stop such problems occurring in the future.