Soil loss estimation and spatial mapping using rules and GIS-A case study in Kurumanpuzha sub watershed of Chaliyar river basin

Abstract

Land degradation is a problem of grave concern and one major factor leading to it is soil erosion. The main aim of the study is to calculate the soil loss in the sub watershed. This study also analysed the quantitative analysis of morphometric parameters of Kurumanpuzha sub watershed using remote sensing data and geographic information system. Morphometric parameters were evaluated from three perspectives: Linear, Areal and relief characteristics. A fifth-order river drains Kurumanpuzha watershed and the drainage network is mainly dendritic type. The mean bifurcation ratio (Rb) was 2.05. The watershed has elongated shape suggesting low peak flows for longer duration and hence easier flood management. The drainage texture analysis revealed fine drainage which implies the dominance of impermeable soft rock with low resistance against erosion. High relief and steep slopes dominates, by which rough landforms (hills, breaks, and low mountains) make up major portion of the watershed. The hypsometric curve with hypsometric integral of 0.48 suggests that Kurumanpuzha watershed is in equilibrium or mature stage of geomorphic evolution. At sub-watershed scale, the derived morphometric parameters were grouped into three clusters (low, moderate, and high) and considerable spatial variability was observed. The results of this study provide information on drainage morphometry that can help better understand the watershed characteristics and serve as a basis for improved planning, management, and decision making to ensure sustainable use of watershed resources. Soil erosion is caused by the action of various factors which are intrinsic to the soil or related to the environment surrounding the soil. These factors include rainfall, soil erodibility, topographic characteristics, crop cover and conservation practices. The Revised universal soil loss equation (RUSLE) is a well-renowned empirical formula which is used to compute the average annual soil loss of a particular area. Remote sensing (RS) and geographical information system (GIS) technologies make modelling and execution of RUSLE easy, reliable and cost effective. So, these were employed to compute the spatial distribution of soil erosion risk area in Kurumanpuzha sub watershed in Kerala state, India. All the factors were generated using metrological data, CartoSat DEM, Landsat 8 imagery using GIS software and integrated in a GIS environment to estimate the soil loss rate. It was found that forest/Dense vegetation 142 (56.46%) was the dominant land use followed by rubber plantation (20.06%) and o scrub land (8.91%). The average annual soil loss of the watershed was estimated to be 8.00 t ha-1 yr-1 and the total quantity of soil eroded was 82,872.4 t yr-1 . The average annual soil loss was highest in bare land (8.55 t ha-1 yr-1 ) followed by scrub land (5.27 t ha-1 yr-1 ). The soil erosion map thus generated can serve as a basis for adopting suitable measures in the watershed for sustainable management of the resources in it.