Estimation of Soil Erosion in Nepal Using a RUSLE Modeling and Geospatial Tool

Pooja Koirala,Subesh Joshi,Raju Chauhan,Sudeep Thakuri

doi:10.3390/geosciences9040147

Abstract

Soil erosion is a major issue, causing the loss of topsoil and fertility in agricultural land in mountainous terrain. Estimation of soil erosion in Nepal is essential because of its agriculture-dependent economy (contributing 36% to national GDP) and for preparing erosion control plans. The present study, for the first time, attempts to estimate the soil loss of Nepal through the application of the Revised Universal Soil Loss Equation (RUSLE) model. In addition, it analyzes the effect of Land Use and Land Cover (LULC) and slope ( β ) exposition on soil erosion. Nation-wide mean annual soil loss of Nepal is estimated at 25 t ha−1 yr−1 with a total of 369 million tonnes (mT) of potential soil loss. Soil erosion based on the physiographic region of the country shows that the Middle Mountains, High Mountains, High Himal, Chure, and Terai have mean erosion rates of 38.0, 32.0, 28.0, 7.0, and 0.1 t ha−1 yr−1. The soil erosion rate by basins showed that the annual erosions of the Karnali, Gandaki, Koshi, and Mahakali River basins are 135, 96, 79, and 15 mT, respectively. The mean soil erosion rate was significantly high (34 t ha−1 yr−1) for steep slopes (β > 26.8%) and the low (3 t ha−1 yr−1) for gentle slopes (β < 5%). Based on LULC, the mean erosion rate for barren land was the highest (40 t ha−1 yr−1), followed by agricultural land (29 t ha−1 yr−1), shrubland (25 t ha−1 yr−1), grassland (23 t ha−1 yr−1), and forests (22 t ha−1 yr−1). The entire area had been categorized into 6 erosion classes based on the erosion severity, and 11% of the area was found to be under a very severe erosion risk (> 80 t ha−1 yr−1) that urgently required reducing the risk of erosion.

Highlights

Soil loss due to erosion is a global problem, especially affecting natural resources and agricultural production [1,2,3,4,5]
The results showed that the Rainfall Erosivity Factor (R) value ranges between 157 and 1981 MJ
Soil Erodibility Factor (K) value ranged from (Figure 3). These raster maps were integrated within the ArcGIS environment using the Revised Universal Soil Loss Equation (RUSLE) relation

Summary

Introduction

Soil loss due to erosion is a global problem, especially affecting natural resources and agricultural production [1,2,3,4,5]. The mean rates of soil erosion throughout the world are estimated to be between. Water erosion is by far the most serious cause of land degradation, with a global estimate of about 11 million km2 [10]. The loss of fertile soil in arable lands and the degradation in the quality of the soil resources are the main on-site consequences of soil erosion [11]. Siltation of water bodies is an important off-site impact of soil erosion [12]. One of the major factors causing destruction and sustainability of agriculture in the upland is soil erosion [13]. Soil erosion by rainfall and surface water flow is generally affected by five factors: Rainfall erosivity, soil erodibility, topography, surface coverage, and support practices [14]

Methods

Results

Discussion

Conclusion