Mangalore is situated on the west coast of India in Karnataka State. Gurpur and Nethravathi rivers join the Arabian sea near Mangalore. Mangalore spit and Ullal spit, located on the north and south of the confluence, respectively, are under continuous change in their morphology due to various complex coastal processes. Remote sensing data and Geographic Information System (GIS) techniques were used to study the shoreline changes in this area. Satellite data of IRS-1B/LISS-II of 1995 and IRS-1C/LISS-III of 1999 and hydrographic chart of 1979 were used for the studies. The analysis was carried out by both raster and vector methods. Raster analysis was carried out using automated method, and vector analysis using manual digitizing method. Results of both the methods compare well. Vector analysis using GIS techniques has been proved useful in studying the change detection and indicated severe coastal erosion of Ullal spit during 1979-1999. Rate of erosion (3.4 ha/year) of the Ullal spit during 1995-1999 was more severe as compared to erosion during 1979-1995 (1.18 ha/year). However, Mangalore spit was found to be almost stable. Considerable accretion on the riverside of both the spits was observed.

The river mouth migration and coastal geomorphology play a major role in stabilization of coastal sand bodies. Human activities also cause immense geomorphologic changes at a rapid rate. For highly dynamic areas such as beaches, coastal inlets, lagoons, spits and river mouths, it is necessary to gather timely information on the dynamics of coastal geomorphology for the purpose of erosion control measures.

Remote sensing data can be effectively used to locate the areas having relatively rapid changes of the coast. Synoptic and repetitive coverage of the satellite data can be successfully used to monitor long-term and short-term shoreline changes and the morphological changes in estuaries. Remote sensing images that have the coverage of significant spatial extents are excellent tools to provide information regarding shoreline and suspended sediment concentration. However, efforts to monitor beach profile changes using remote sensing data have to be supported with the associated measurements of sediment quantities so that useful decisions on coast management and financing options can be made. Geographic Information System (GIS) incorporating temporal changes in the bathymetry of a region can be effectively used to identify the volumetric change of coastal sediments over time together with the associated beach profile change. The analysis needs to be performed on the same base data to identify the nature of any relationship between the volumetric changes of sediment in a beach section over time and along shore movement of sediments over the same period of time.

Gurpur and Nethravathi rivers join the Arabian sea near Mangalore. Mangalore spit and Ullal spit, located on the north and south of the confluence, respectively, are continuously changing their morphology. The objective of this study is to analyze the long-term and short-term morphological changes in Nethravathi spit complex and detecting the changes using remote sensing data and GIS techniques.

Environmental Sciences Journal, GIS Techniques, Nethravathi Spit Complex, Geographic Information System, Coastal Geomorphology, Remote Sensing Data, Coast Management, Hydrographic Charts, Ground Control Points, Mathematical Models, Mangalore Spit, Geoinformatics Techniques, Morphological Dynamics.