Bhat H, Gangadhara 
3 RESULTS 
The barrier spits are the most dynamic features, as seen by the changes in their configuration over the years. Because of this 
reason spit development on either side of the three estuarine mouths have been studied in detail. The northern spit of 
Nethravathi -Gurupur estuary (Bengre spit) shows growth towards south, whereas Mulki-Pavanje and Udyavara have 
their longer spits pointing to the north. Comparison of the 1967 maps with those of 1910-1912 and 1949 shows accretion 
of Ullal spit and erosion of Thannirbhavi and Bengre spit. Maps generated based on aerial photographs of 1979 and 
satellite images of 1988 and later periods show a reversal of trend ie., accretion of Bengre and erosion of Ullal spits. 
Maps of 1996 and 1998 show rapid widening of the Bengre beach and further narrowing of the Ullal spit. 
The multidated data products study also indicates the gradual shifting of the estuarine mouths of Nethravathi-Gurupur, 
Mulki - Pavanje and Udyavara to the north. Mulki- Pavanje shows the development of a large bar in front of the estuarine 
mouth. Presence of beach ridges near Panambur, Hejamady-Padubidri and north of Udyavar and widening of the beaches 
to the north of Bengre, Suratkal and Udyavarasuggests prevalence of depositional environment. Beach erosion has been 
reported at Someshwara, Ullal, Mukka-Sasihitlu, south of Hejamady, Kapu and Near Udyavara in the past. 
There have been considerable changes in the morphology of the barrier spits. Some of these modification can be ascribed to 
human interference by way of construction of engineering structures. The breakwaters of New Mangalore Port, the 
breakwaters at the mouths of Nethravathi-Gurupur estuary, Udyavara estuary and seawalls elsewhere have contributed 
substantially to the modification of shoreline. The Bengre spit which was a site of erosion turned into an accreting zone 
subsequent to the construction of a seawall at the southern tip of the spit and the breakwaters at the mouths of Nethravathi- 
Gurupur estuary. The consequence of this was severe erosion in the Ullal spit. Northern part of New Mangalore Port 
which was a stable area prior to construction of breakwater during the mid seventies, shows an accreting trend. Construc- 
tion of sea-walls (to protect the beaches against erosion) have resulted in shifting of erosion sites to the downdrift 
(southern) side. 
  
Table 1: Changes in the position and width of Nethravathi-Gurupur estuarine mouth between 1910 and 1998 
SLNo. Period Data Products Position of the Nethravathi-Gurupur River Mouth 
From To Width 
1 1910-1912 Survey of India 
Topographical Maps 12°30" 10” N - 12° 50° 22”N 375m 
2 1949-1960 Naval Hydrographic 
Charts 120 50’ 22” N - 12°50> 34”N 360m 
3 1967 Topographical maps 12°50’ 37” N - 12° 50’ 42”N 150m 
4 1979 Naval Hydrographic 
charts 12° 5024” N - 12°50>42”N 550m 
5 1982 Topographical maps 12° 50° 41”N- 12°50> 51>N 350m 
6 1992 Indian Remote Sensing Satellite 
Imagery (IRS) 12°50° 44” N- 12°50> 53"N 250m 
7 1996 IRS imagery 
(Geocoded) 12° 50° 44” N - 12°50> 51”N 225m 
8 1998 IRS imagery 
(Geocoded) 12°50*18”N - 12°50> 32>N 425m 
  
194 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.