Using GIS and RS to Evaluate Shoreline Changes in Sea Turtle Nesting Sites on The Southern Coast of Sri Lanka Over 15 Years Period

Abstract

Out of the seven sea turtle species, five species come to Sri Lankan coastal belt for nesting. Southern coast of Sri Lanka comprises most of the known marine turtle rookeries, due to the availability of foraging and nesting grounds. But the threats to nesting turtles are very high in these areas due to various human, animal, and physical factors that affect negatively. Coastal erosion can be considered as one of the most severe physical threats. This study was carried out to identify shoreline changes in selected turtle nesting sites in southern coast namely Kosgoda, Habaraduwa, Mirissa, Rekawa, Kalamatiya, Ussangoda, Uraniya in Bundala and between Mahaseelawa and Patatupana in Yala. Google Earth high resolution satellite images were used to extract the instantaneous shoreline over a period of 15 years. Shorelines were digitized referring to wet dry margin and saved as KML file format. KML file was converted in to layer file by Arc GIS 10.8 software. Transects were casted using manually created baseline. Shoreline change statistics such as Net Shoreline Movement (NSM) and End Point Rate (EPR) were calculated. Results respectively for the above-mentioned sites are NSM values (m) of 3.51, 2.67,−2.26, −20.88, 15.72, 5.79, 19.79 and 7.19 and EPR values (m/yr) of 0.57,0.43, −0.41, −3.96, 3.12, 1.15, 2.81 and 1.23. That indicated Mirissa and Rekawa beaches are eroded while other sites are accreted. It may be due to development activities, sand mining, destruction of coastal vegetation and coral reef, etc. Especially Rekawa being one of the main sea turtle rookeries, these long-term trends can be very important to study further. Furthermore, seasonal erosion and accretion cycles play a key role in maintaining the quality of nesting environment. Therefore, in situ nest monitoring and turtle conservation projects supported by data on long term and seasonal erosion and accretion cycles are needed to protect them.