Most of the mountainous regions in tropical humid climatic zone experience severe soil loss due to natural factors. In the absence of measured data, modeling techniques play a crucial role for quantitative estimation of soil loss in such regions. The objective of this research work is to estimate soil loss and prioritize the sub-watersheds of Kali River basin using Revised Universal Soil Loss Equation (RUSLE) model. Various thematic layers of RUSLE factors such as rainfall erosivity (R), soil erodibility (K), topographic factor (LS), crop management factor (C), and support practice factor (P) have been prepared by using multiple spatial and non-spatial data sets. These layers are integrated in geographic information system (GIS) environment and estimated the soil loss. The results show that ∼42 % of the study area falls under low erosion risk and only 6.97 % area suffer from very high erosion risk. Based on the rate of soil loss, 165 sub-watersheds have been prioritized into four categories-very high, high, moderate, and low erosion risk. Anthropogenic activities such as deforestation, construction of dams, and rapid urbanization are the main reasons for high rate of soil loss in the study area. The soil erosion rate and prioritization maps help in implementation of a proper watershed management plan for the river basin.
Hypsometric analysis is useful for understanding the geomorphic stages of a river basin. Hypsometric parameters have been evaluated and curves are prepared for all the 20 sub-basins of Kali River. Thirteen sub-basins are found to be under younger geomorphic stages with high hypsometric integral (Ea) values and subjected to recent tectonic activities. The remaining seven sub-basins are approaching mature stage and subjected to more erosion and less impacted by recent tectonic activities. Six sub-basins with lower hypsometric head values (50.56) indicate least effect of diffusive processes and another six sub-basins with medium hypsometric head values (0.60-0.68) depict moderate diffusive erosion. The remaining eight sub-basins with higher hypsometric head values (40.75) indicate highest diffusive processes at their upper reaches. Lower (50.28) and higher (40.44) hypsometric toe values indicate minimum and maximum mass accumulation respectively at the sub-catchment mouth.
ABSTRACT:To assess the relative tectonic activity classes, five geomorphic indices such as stream-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), valley floor width -valley height ratio (Vf) and drainage basin shape (Bs) of ninetyfour sub-basins of Valapattanam river basin have been analysed by applying the standard formulae. Relative tectonic activity classes (Iat) obtained by the average (S/n) of different classes of geomorphic indices have been classified into three groups. Group I shows high tectonic activity with values of S/n < 2; group II shows moderate tectonic activity with S/n > 2 to < 2.5; and group III shows low tectonic activity with values of S/n ≥ 2.5. Field evidences such as deep valleys, sudden changes in the river course and waterfalls at fault planes clearly agree with the values and classes of tectonic geomorphic indices.
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