Objectives of the Study
- Development of a soil erosion intensity map using modified universal soil loss equation with the aid of remotely sensed data in a GIS environment, and
- Watershed
prioritization with respect to soil erosion
intensity.
Study Area
The study was carried out at the basin of the Bata river (Figure 01) which is a tributary of Yamuna river. It is located between 300 25' 3.33" N to 300 35' 13.71" N latitude and 770 22' 34.75" E to 770 39' 42.31" E longitude. The maximum stretch of this region is from east to west 26.68 Km, whereas its north-south stretch is only 14.7 km. The total area drained by the river Bata being 268.6769 km2. The Bata river basin, which is bounded by the sinuous and meandering Giri river in the North and East, by the mighty Yamuna in the South-East. The Bata river basin has a sub-continental mountain type of sub-tropical monsoon climate with moderately warm to hot summers, high monsoon rains and a cool to cold winter season.
Materials Used
| 1. Remote Sensing
Data |
Path |
Row |
Date |
| a.
IRS-1DLISSIII |
96 |
50 |
12th Oct,
1998 |
| b.
IRS-1DLISSIII |
96 |
50 |
01st Mar.
1998 |
| c.
IRS-1DPan |
96 |
50 |
08th Oct,
1999 |
|
2. SOI Toposheets |
|
|
|
|
Sheet No |
: |
53/F/6,F/7,F/10 and
F/11
|
|
Scale |
: |
1:50,000
|
|
Date Surveyed |
: |
1965
|
|
3. Ancillary Data |
|
|
|
| Meteorological
data Station |
|
Date |
|
Dhaulakuan |
|
1998-99 |
| Paonta |
|
1968-77 |
| Renuka |
|
1971-91 |
| Nahan |
|
1971-91 |
Pedological map
Soil map |
|
(Geoscience Division, IIRS)
(Dept. of Soil Science, Krishi Vishwavidyalaya, Palampur, 1997)
|
Land use/ cover Classification
In this study supervised classification was employed to prepare the land use/ cover map of the study area. In this study, best results were obtained from maximum likelihood classifier. Using this classifier, Bata river basin was classified into eight land use/ cover classes namely Dense Forest, Moderate Forest, Open Forest, Wheat Crop, Sugarcane, Settlement, River Bed and Water Body.
A 12-day intensive field checking effort was made in order to collect ground truth information. Initially, a rapid reconnaissance survey of the study area was carried out in order to observe the relationship between the interpreted land use/ cover, physiography and actual in the ground as well as to fix up sample sets for the survey area.
Preparation of DEM, slope map and aspect map
To create a Digital Elevation Model (DEM) of Bata river basin, contour segment map and spot-height point map were prepared by digitizing contour lines and spot-heights from the SOI topo-sheets No 53 F/6, 7, 10 and 11 (1965, 1:50,000 scale). Interpolation of this combined contour map and point map was done in ILWIS software.
Determination of factors of Modified USLE
Revised USLE - RUSLE uses the same empirical principles as USLE, however it includes numerous improvements, such as monthly factors, incorporation of the influence of profile convexity/concavity using segmentation of irregular slopes. For this study improved empirical equations were used for the computation of rainfall erosivity (R) (Fournier, 1960), topographic (LS) factor (Foster & Wischmeier, 1974) and crop management (C) factor (Lal, 1994).
Modified R factor
Fournnier (1960) developed an erosivity index for river basins. The index described as climate index C is defined as follows:
C = r
2/P
where, r is the rainfall amount in the wettest month and P is the annual rainfall amount. This index was subsequently modified by FAO as follows:
C
i =
12S
I=1 (ri2/P)
where, Ci is the climate index, rI is the rainfall in month i and P is the annual rainfall. This index is summed for the whole year and found to be linearly correlated with EI30 index (R) of the USLE as follows:
R = b +a*(C
i)
where, the constants a and b vary widely among different climatic zones.
Table 1
. Climate index and R factors for Bata river basin at various stations
|
Dhaulakuan(97-98) |
Paonta(68-77) |
Renuka(71-91) |
Nahan(71-91) |
| Annual
average |
size=1>2130.60 |
size=1>1611.40 |
size=1>1082.50 |
1883.80 |
| Climate
index |
547.91 |
386.20 |
191.34 |
413.06 |
| R
factor |
size=1>1189.30 |
size=1>1055.56 |
894.61 |
1077.75 |