Indian Journal of Geo Marine Sciences Vol.46 (04), April 2017, pp. 771-773 A wake up call for protecting Digha coast, West Bengal, Northeast coast of India J.Selvin Pitchaikani1* & Subrat Mukherjee2 1ICZM Project, State Project Management Unit, Institute of Environmental Studies & Wetland Management, DD-24, Sector-I, Salt Lake City, Kolkata 700 064, West Bengal, India 2West Bengal Pollution Control Board, Salt Lake, Kolkata 700098, West Bengal, India *[E.Mail: [email protected]] Received 05 December 2014 ; revised 09 January 2015 Erosion is a major issue in Digha-Sankarpur Irrigation, Govt. of West Bengal constructed coastal area. Digha is a seaside resort town geotube for about 1km stretch in 2007 on trial located at Purba Mednipur District of West basis from Sankarpur to Jalda coast of Purba Bengal along the east coast of India at Latitude Mednipur District of West Bengal. Geotubes are 21°37’.25 N and Longitude 87°31’ 35 E. Digha is sediment-filled sleeves of geotextile fabric to located 187 km from Kolkata and a large number control the erosion along the coastal stretches. of people are visiting for a couple of days to However, this geotube also failed to protect the delight in and blend themselves to its unique erosion and the system has collapsed during Aila sublime and serene ambience. This coastal area 20095. Aila is a super cyclone which hit the West has been experiencing severe erosion issue due to Bengal coast on 25th May, 2009. The established various natural and manmade activities. geotube could not withstand the Super cyclonic Longshore sediment transport is one of the main force having a magnitude of 82km/hr. In New factor for severe erosion in coastal areas1-2. Digha, the Low Water Line (LWL) has shifted by Sediment transport is controlled by wave about 240m towards the land in front of the Jatra dynamics and bathymetry of the region3. Littoral Nala Sluice gate in comparison between 1936 and drift processes is dominant along east coast of 2011(Fig.1). So it is time to think about some new India being predominantly net northerly drift4. suitable designs for the Digha coast to protect the Transport of sand material in the longshore coast from erosion and for the sustainable direction by waves and currents near the shore is development of the coast. known as littoral drift. Presently the palisades (wooden poles) were erected along Sankarpur- Jalda stretch of West Bengal coast to protect the shore from severe erosion. At the same time seawalls along with buffer blocks are also constructed along Digha coast from Old Digha to New Digha (about 1.5 km stretch). Seawalls and buffer blocks could dissipate attenuating the incident wave energy at certain level. Basically, wooden poles failed to trap the sediments which are being transported by long shore current. Similarly, natural stone and boulders are also not Fig.1.Showing the shifting of HWL from 1936 to 2011 in Digha (Source: Dept. of Irrigation WB) environment friendly. So, the Department of 772 INDIAN J. MAR. SCI., VOL. 46, NO. 04, ARIL 2017 Similarly, eastern side of Old Digha, stretch is wave and tidal current which acts from the marine facing severe erosion during flood tide. side are playing an important role on coastal erosion. It is believed that the thorough understanding on the coastal processes could be useful to design the structure, height of the structure, orientation of the structure etc. In order to protect the erosion at Old Digha, boulders dumped in Seahawk hotel side (Fig.3) and the dumped boulder area has been surveyed with handheld GPS (Juno SB series). Shoreline has shifted about 92.5 meters towards land during 2002 to 2014 (Fig.4 & 5). Fig.2. Seawall with buffer blocks at Digha coast At the same time the western side is being protected by a seawall with buffer blocks (Fig.2). Though, the seawall along with the buffer blocks are dissipating the wave energy up to certain level, it's not an opt protection measures. The coastal inhabitants are suffering from panic of massive coastal erosion within a couple of years, as the trend of erosion continues unchecked, particularly in the areas immediately adjacent to the constructions. Since, Digha is emerging as an important tourist hub in West Bengal, and the Fig. 3. Boulders at Old Digha various developmental activities are in progress along the coast under the World Bank funded ICZM project, it is essential to find out suitable structure to protect the Digha coastal stretch from erosion. The scientific study related to hydrodynamics; wave climate and sediments dynamics are meager in this region. Since the geotube system has been unsuccessful in this coast, it is very important to understand about the coastal processes in the West Bengal. Basically, the sediment supply and sediment transport are responsible for the erosion. Wave action and tidal current together are influencing the shoreline changes. Fig.4. Old Digha in 2002 The coastal area includes part of the Balasore-Contai coastal plain between Subarnarekha River mouth, (western side) in the Orissa State and Rasulpur River (eastern side) in the West Bengal State. This coastal belt exhibits varied interaction of physical processes viz. fluvial, fluvio-tidal and marine coastal processes of tides, waves and winds. The Bengal basin is characterized by the presence of an extensive marine-coastal tract bordered by the Bay of Bengal. Coastal geomorphology of Digha- Shankarpur is primarily controlled by the coastal sediment dynamics. Interplay between clastic sediments which are being introduced from rivers Fig.5. Old Digha in 2014 of variable magnitude and the strength of the PITCHAIKANI & MUKHERJEE: A WAKE UP CALL FOR PROTECTING DIGHA COAST 773 Acknowledgement The first author is indebted to Project Director, ICZM Project, West Bengal, Department of Environment, Government of West Bengal for providing the support and encouragement, and Irrigation department for data sharing and the World Bank for the grant (Credit No. 4765-0IN). References 1. Bijker E W, Longshore transport computations. Journal of the Waterways, Harbors and Coastal Engineering Division, 1971. 97(4):687-701. 2. Chandramohan P, and Nayak., Distribution of Fig.6. High water line at New Digha longshore sediment transport along the Indian coast based on empirical model. in 3rd Ind. Natl. Conf. Nearly 26443.1 sqm of land area (marked in red on Dock and Harbour Engrg.1989. color in Fig.4) has eroded due to non- cohesive 3. Sanilkumar V, Raju N, Pathak K, and Anand N. sediment transport by long shore current and by Nearshore processes along north Karnataka coast. various coastal processes prevailing in the coastal in Intl. Conf. on Ocean Engrg.1997. region. Since Old Digha is not at all suitable for 4. Kunte PD, Alagarsamy R, Hursthouse AS, Sediment fluxes and the littoral drift along bathing and hence tourists prefer to take bath in northeast Andhra Pradesh New Digha. However, high water line in New 5. Coast, India: estimation by remote sensing, Digha is reaching up to sluice gate (Fig.6), so it is Environ Monit Assess. 2013 Jun;185(6):5177-92. essential to take measures to protect the Digha 6. India Meteorological Department, Severe Cyclonic Storm, AILA: A Preliminary Report, http:// www. coast from the erosion for sustainable coastal zone imd.gov.in/ section/nhac/dynamic/aila.pdf. 2009. management practices. .