Theme 8-11-Geomorphological studies of netravathy and Gurpur river estuary in the west coast of India using remote sensing data.

Abstract

The West flowing rivers originating in the mountainous region of Western Ghats, climb down to the narrow coastal alluvium and flows parallel to the sea coast to a considerable distance before joining the sea. In the process, the river carries large quantity of sediment down the hill all along the river course. A unique feature of these rivers is that, two or three rivers with independent catchments join together at the estuary before joining the sea. Due to the dynamic nature of rivers as well as the ocean, changes in the estuary and also along the river course are very common. Most of the rivers in the coastal region overflow to the adjoining land, invariably submerging the agricultural fields during peak monsoon. These rivers being seasonal, large amount of sediment is deposited in the coastal plains giving rise to sand dunes and shoals in the river estuaries as well as in the river coarse. Netravathi and Gurpur rivers are one such combinations of West-flowing rivers joining together on the Western side of the city of Mangalore before joining the Arabian Sea. The river estuary on the sea-side is quite unstable giving rise to sea erosion on either side of the estuary. The sediment deposition all along the rivers with varying sizes of sand dunes and shoals are observed in the river course. The industrial development activities on the bank of Gurpur river has changed the land cover on the river bank to a great extent. Multi-temporal remote sensing data are used to study both long term and short term changes both in the river estuary and along the river upstream. The visual interpretation techniques are used to analyse the changes in the river course and also in the estuary. The results are compared with both field observation and ground truth data. Both qualitative and quantitative analyses are carried out. Frequent changes on the sea-side of the estuarine are established. However, the riverbanks seem to be almost stable over the years. The possible reasons for undisturbed river course are established. The changes in the size and shape of the sand dunes as well as those of shoals are quantified.