Abstract:
This study mainly focused to identify the erosion prone areas in Kunthippuzha
sub-basin using RUSLE as well as MMF model. The effect of spatial and temporal
variations of land use-land cover on soil erosion was analysed with the help of NDVI
values. The estimation was performed for the year 2000 and 2013. The mean soil
erosion estimated for the year 2000 was 18.30 and 20.58 t/ha/y respectively by MMF
as well as by RUSLE model. Similarly in the year 2013, it was 32.78 and 35.10
t/ha/y respectively.
To find the erosion prone areas in the sub-watershed factorial scoring method
was chosen, in which pixel based scoring was done based on mean soil erosion value
obtained under each layers of landuse, rainfall, slope and topographic raster. From
the study based on the RUSLE model, 0.15% of the area experienced very slight
erosion.
40.70% of the area was with slight erosion, 28.76% area was under
moderate erosion, 22.61% of the area was under severe range and 6.15% area was
under very severe range. According to MMF model, the areal extent observed under
slight, moderate, severe and very severe risk categories was 39.02%, 36.94%,
14.92%, 7.50% respectively.
NDVI values corresponding to land use were identified, in which negative
NDVI values correspond to water pixels whereas higher NDVI values represents the
thick vegetation. From the analysis of the temporal variation in land use over the
NDVI, it was observed that NDVI value decreased at the points where density of the
canopy decreased. The spatial variation of soil erosion varies pixel to pixel according
to the landuse pattern. Highest soil erosion risk was observed under built-up plus
barren land. Sediment Delivery Ratio (SDR) was calculated for the entire sub-
watershed, which shows that most of the eroded sediments get deposited at
intermediate location before reaching the outlet. The SDR calculation enhances the
importance of adopting GIS technology in soil erosion assessment.
