SEA EROSION

The landward displacement of the shoreline caused by the forces of waves and current is termed as sea erosion. The main causes of the sea erosion include both natural causes like action of winds waves, tides, storms etc. and anthropogenic activities including construction of artificial structures, mining of beach sand, offshore dredging, or building of dams or rivers. In addition to that, various catastrophic events also trigger coastal erosion which include tsunamis, tectonic movement etc. The coastlines are threatened by a combination of human pressures and climate change and variability arising especially from sea-level rise, increases in sea surface temperature, and possible increases in extreme weather events. Key impacts include accelerated coastal erosion, saline intrusion into freshwater lenses, and increased accelerated coastal erosion, and increased flooding from the sea. Sea-level rise will exacerbate inundation, erosion and other coastal hazards; threaten vital infrastructure, settlements and facilities.

            Studies conducted by the National Institute of Oceanography in the northern part of Indian Ocean in the last 40 years concluded that the sea level rose by 1.06-1.75mm/year in the past century. Scientific studies on climate change show that the period up to the end of the century and beyond project a likely rise in sea level of the order of 55-60mm. Survey of India has established 26 tide gauges. All of these tide gauge stations are transmitting data in real time to the Indian National Centre for Ocean Information Services (INCOIS), Hyderabad under the Ministry of Earth Sciences (MoES).

            Various approaches can be adopted to effectively manage erosion. The main approaches adopted are as follows:

            Backshore management: This approach will involve relocation and allows natural processes to continue with possible strategic benefits spread over adjacent areas. Also, it does not involve any management costs.

            Dune grass planting: The technique will involve vegetation which encourages dune growth by trapping and stabilizing blown sand. These natural dune grasses act to reduce wind speeds across the surface, thereby trapping and holding sand. They grow both vertically and horizontally as the sand accumulates. Marram grass is particularly effective as it positively thrives on growing dunes, and is perhaps the easiest to transplant.

            Dune Thatching: Thatching is a traditional way of stabilising sand, and protecting vegetation which involves waste cuttings from forestry management, or other low cost materials. Well laid thatch will encourage dune recovery and will resist some erosion, but cannot prevent erosion where wave attack is frequent and damaging. The thatch reduces surface wind speeds, encouraging deposition of blown sand.

            Dune Fencing: Construction of semi-permeable fences along the seaward face of dunes will encourage the deposition of windblown sand, reduce trampling and protect existing or transplanted vegetation. A variety of fencing materials can be used successfully to enhance natural recovery. Fencing can also be used in conjunction with other management schemes to encourage dune stabilisation and reduce environmental impacts.

Scheme in Operation

            In XI Five Year Plan, specific anti-sea erosion problems have been addressed under State Sector scheme – Flood Management Programme of Ministry of Water Resources. Though anti-sea erosion works are planned and executed by the State Governments, realizing the severity of sea erosion problems in certain reaches of the coastline , MoWR initiated the process of collecting details of severely affected reaches with a view to exploring the possibility of preparing a National Coastal Protection Project (NCPP) and taking up the same for external assistance.

            India and Asian Development Bank (ADB), initiated a Technical Assistance on preparing a Sustainable Coastal Protection and Management Project for the States of Goa, Karnataka and Maharashtra initially. This broadly supports National Coastal Protection Project (NCPP).Appropriate protection measures arising out of the coastal erosion are addressed jointly by respective state governments and the Central Water Commission.