IDENTIFICATION OF FLOOD BREACHING ZONES USING GIS FOR CHIDAMBARAM TALUK, CUDDALORE DISTRICT, TAMILNADU, INDIA

摘要

The study area Chidambaram taluk falls north of Coleroon River and comprises both the northern and southern parts of Vellar River. The taluk forms the northern most tip of the Cauvery delta. The region consist of the flat low lying flood plain deposits, natural levee deposits, coastal plain and a lagoon barrier island complex i.e. transitional environment in a marginal marine setting. The study area falls in between two major rivers; hence the area is subjected to frequent flooding during monsoon seasons. In the taluk one of the major reservoirs is Veeranam Lake, when this reservoir is full during the monsoon the danger of flooding becomes more. In the recent past in the year 2005 and 2008 the monsoon was unexpectedly high both in the study area as well as in the catchments area. As a result of that the taluk was flooded with rain water. In the month of November and December 2005 and 2008 due to north east monsoon, Tamilnadu experienced two weeks of continuous rainfall owing to a depression developed east-southeast Bay of Bengal, that had moved closer to the state's coast, causing heavy rains and flash floods in low-lying areas of south coastal districts of Tamilnadu of and Pondicherry. The past flood in the year 2005 and 2008 was due to long rain flood. As the volume of the water in the Vellar and Coleroon greatly increased the erosive power also increases accordingly. The river caries a much higher sediment load. Due to the heavy deposition of siltation after every monsoon large reservoir, tanks and irrigation canals gets silted ultimately leading to the flooding during the next monsoon. Geodata base for the flood zones were developed for the study area as the Geodatabase provides Centralized spatial and attribute storage which is easy to use standard behaviors rules with multiple customization option. The proximity buffer tool analysis results buffer zone which clearly demarcates the inundation of flood water through the breach points. As the slope of the terrain at Orathur is about 2 -3 degree the breaching of the Vellar River inundates the northern part of the Chidambaram Taluk. In the Komaratchi and adjoining area the Khan Sahib canal is the major threat as the excess of water is being drained through this canal only which mainly drains the major part of the Chidambaram flood plain. In the present study it is tried to bring out the breaching zones of the Velar and the major and minor roads using GIS as a tool.