d remote 
by INSA 
and Soils, 
ns, New 
l analysis 
“Remote 
ystems — 
ublishing 
IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring", Hyderabad, India,2002 
ESTIMATION OF USLE PARAMETERS FOR A HARD ROCK CATCHMENT USING GIS 
TECHNIQUE 
B. K. Purandara and Dilip G. Durbude 
Hard Rock Regional Centre, National Institute of Hydrology, Hanuman Nagar, Belgaum- 590 001(Karnataka) 
dgdurbude@yahoo.com 
KEY WORDS: GIs, ILWIS, Soil loss, USLE, Erosion 
ABSTRACT: 
Land degradation from water induced soil erosion is a serious problem in India and only fragmentary information on factor affecting soil 
erosion is available. Therefore, an attempt was made to estimate the soil erosion from a hard rock catchment, viz. Malaprabha 
Representative Basin having a catchment area of 540 sq. km. Soil investigations losses for a number of stations (26 stations) were 
estimated using the Universal Soil Loss Equation (USLE) over different land use conditions of the catchment. Since, soil erosion is a 
complex phenomenon governed by a large of factors, such as rainfall erosivity, soil erodibility, slope, land use and conservation 
measures. Twenty-six plots were selected for USLE parameter estimation each representing various land use covers based on field and 
laboratory investigations. Estimated parameters were compared with the parameters obtained through GIS technique, which showed a 
very good correlation. The study further revealed that the quantity of soil eroded in areas covered by black cotton soils are quite high 
(often exceeds 10 tonnes/ha/year) as compared to red soil areas. Results of the analyses are presented in the form of iso-erodant map of 
the catchment area. 
1. INTRODUCTION 
Soil and land use/cover have become extremely competitive 
not merely in India but all over the world because of the 
tremendous pressure of growing population in recent years. The 
problem of soil erosion in India, their extent, severity and 
nature vary greatly in different parts of the country depending 
upon climate, topography, soil, land use and also in the pattern 
of agricultural economy and increasing human livestock 
population. In 1975, Indian Agricultural scientists estimated 
that 6.6 billion tons of soil is eroded from India’s cropland each 
year and about 60% of the cropland are eroding excessively. 
An estimated area of about 175 million hectares constituting 
53.3 percent of Indian’s geographical area of 328 million 
hectares is subject to various kinds of degradation problems. 
Active soil erosion, by water and wind, alone accounts for over 
140 million hectares which amounts to about 6000 million tons 
of fertile soil causing a nutrient loss of about 5.33 million tons 
of NPK costing around Rs. 700 crores. About 1572 million tons 
are washed into the sea while 480 million tons are getting 
deposited in various reservoirs of India. At present days, soil 
erosion is taking place at the rate of 16.35 tons/ha/annum, 
which is more than the permissible limit of 4.5 -11.2 
ton/ha/annum. 
The study of soil erosion is primarily dependent on rainfall 
erosivity, ground cover, soil erodibility, slope length and 
erosion control measures. Rainfall initiates soil erosion by 
causing detachment of soil particles and transporting then 
overland. Wischmeier and Smith (1958) have shown that the yield of 
sediment is proportional to the EI30 index. Le. the product of 
maximum 30 — minute intensity (130) and the kinetic energy of the 
(E) of the rainfall as reported by earlier researchers. Therefore, the 
erosion factor may be expressed as the relation between the erosivity 
of rainfall , i.e., the potential ability of rain to cause erosion and soil 
erodibility , i.e. the susceptibility of the soil to erosion. Rain as the 
principal erosion agent is usually characterised by intensity, size of 
rain drop and rain drop velocity, soil properties which are expressed 
by coefficients showing the effects of soil texture and structure of the 
soils and by other factors affecting the origination and course of 
erosion processes, namely slope gradient, slope length and the 
vegetation cover. 
Universal soil Loss equation combines all these parameters and 
provides an estimate of soil erosion for all practical purposes. 
Therefore, in the present study USLE method is adopted for the 
estimation of soil erosion in Malaprabha sub-basin and the results are 
compared with the erosion estimate obtained through GIS (ILWIS) 
technique. 
Study Area 
The Malaprabha sub-basin lies in the extreme western part of the 
Krishna basin. It extends in between 74° 20' and 74°30' E longitudes, 
and 15° 20' and 15 °40' N latitudes and encompasses an area of 540 
sq. km of the Belgaum district in the Karnataka state. It is the major 
source of water yield for the Naviluteerth Dam constructed at 35-45 
km downstream of its mouth. The location of the study area with 
various hydrometeorological network is given in figurel. 
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