Wetland Mapping and Change Detection in Part of Barak Valley Using Remote Sensing and GIS P. Phukon Department of Geological Sciences, India Email: p_phukon@rediffmail.com, A. A. Laskar Department of Geological Sciences, Gauhati University The Barak river system is the second largest drainage network in north east India with a total catchment area of about 39390 kmē that spread over India (30155 kmē), part of Myanmar (840)and Bangladesh(7780 kmē). In India it covers the western part of Manipur, south Assam districts of Cachar, Karimganj and Hailakandi, southern part of North-Cachar hills and Meghalaya and the northern parts of Mizoram and Tripura. The popularly known term ‘Barak Valley’ comprises the three districts of Cachar, Karimgnj and Hailakandi having a total geographical area of 6950 kmē(Cachar 3720 kmē, Karimganj 1870 kmē, and Hailakandi 1327 kmē). In the alluvial reach of the river in Barak Valley numerous wetlands have developed by the fluvial processes apart from a few having formed by tectonic processes. These wetlands have played a major socioeconomic role in the Barak valley which is having high population density and thriving primarily on an agricultural economy. The present study is an attempt to inventories the wetlands of the Cachar district in Barak valley and study their variability in space and time from temporal data spanning over 85 years. As per the 1918 data source (SoI topomap in 1:63360) total area under wetland was about 29.98 kmē with an average density of 1.31 Hectares/ kmē (maximum 12.03 Hectares/ kmēat places). In 1965 there was marginal changes in the wetland coverage, which stands at 29.74 kmē with an average density of 1.26 Hectares/ kmē. However, remote sensing data (IRS L3, FCC) for the year 2004 shows the total area under wetland to be about 14.10 km2 – 59% less than the coverage in 1918. The wetland density has also come down to an average of 0.65 Hectares/ kmē with a maximum of 7.76 Hectares/ kmē during this time. Study of three large individual wetlands viz., Chatla, Bakri and Hilara further shows a loss of wetland area by 73%, 48.4% and 48.4% respectively during 1918-2004. The study also indicates a higher rate of loss of wetland during 1965-2004 than the period 1918-1965.