Bhat H, Gangadhara 
  
1 INTRODUCTION 
Studies relating to long-term shoreline changes using aerial photographs ( Davis, 1976; Dolan et al., 1979, 1980; Leatherman, 
1979, 1983; Leatherman and Zaremba, 1986; Stafford, 1971; Stafford and Langfelder, 1971; Wahle, 1973; Smith, 1990) 
and using satellite images ( Nayak and Sahai, 1985; Prabhakar Rao et al., 1985; Shaik et al., 1993; Wagle , 1982, 1989: 
Gangadhara Bhat and Subrahmanya, 1993; Gangadhara Bhat, 1995; Ramasamy , 1992; Chen and Rau, 1998 and others) 
have been carried out by many researchers. Because of their synoptic viewing capability, multispectral observations and the 
repetivity , the remotely sensed data products are extensively used for detecting long-term shoreline changes and to know 
the evolution of the coastal and nearshore areas. 
A coastline of about 100 km in Southern Karnataka, India has been investigated in the present study. It extends from 
Talapady ( 12°46’N and 74° 52’ E ) in the south to Udupi (13° 21°’N and 74° 44’ E ) in the north.. The shoreline of the 
study area is straight and covered with sandy beaches except at two or three places where it is rocky. The area enjoys a 
humid tropical climate and receives an annual rainfall of more than 3.5 m. The important rivers draining this area from 
south to north are Nethravathi, Gurupur, Pavanje, Mulki and Udyavara (Fig. 1). The Nethravathi and Gurupur rivers 
originate above the Western Ghats and flow for a distance of 148 km and 87 km respectively and have a common exit to 
the Arabian sea near Mangalore. They cover a drainage area of about 4260 km?. The other three rivers originate below 
the Western Ghats and are having lengths less than 40 km. The waves approach the shoreline of this area from WNW and 
NW during post-monsoon season with maximum wave heights of 2-2.5 m and WSW, SW and W with maximum wave 
heights of over 4 m during monsoon season. The southern Karnataka coast has a microtidal environment with a mean tidal 
range of 1.22m (Subrahmanya, 1998). 
The present study has been undertaken to understand the various coastal processes operating in this sector and to analyse 
the shoreline changes over the past 90 years. The study also aims at evaluating the effects of coastal structures on the 
adjacent shorelines and also to know the evolutional history of the coastal zone. 
2 MATERIALS AND METHODS 
Survey of India topographical maps on 1: 63,360, 1:50,000 and 1:25,000 scale surveyed during 1910-1912, 1967 and 1980 
respectively; 1:50,000 scale aerial photographs photographed during 1979; Naval Hydrographic charts on 1:15,000 scale 
(1980) and Indian Remote Sensing satellite data products surveyed during 1988, 1992, 1994 , 1996 and 1998 period in 
different scales have been used. All the aforementioned maps have been brought to the same scale of 1:50,000 using an 
optical pantograph and the changes that took place over the past 90 years have been recorded . The area influenced by 
tides is negligible on this scale, since the difference between the mean low tide and the mean high tide is 1.5 m and the 
submergence of the land along the shoreline is less than 5-6 m during the high tide period. However the cartographic 
accuracy has been maintained with sufficient care by comparing the multidated data products of post-monsoon season. 
  
192 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.