New Insight on Soil Loss Estimation in the Northwestern Region of the Zagros Fold and Thrust Belt

Arsalan Othman,Ahmed Shihab,Syed Hasan,Diary Al-Manmi,Veraldo Liesenberg,Younus Al-Saady,Ahmed Obaid,Ahmed Al-Maamar

doi:10.3390/ijgi10020059

Abstract

Soil loss is one of the most important causes of land degradation. It is an inevitable environmental and socio-economic problem that exists in many physiographic regions of the world, which, besides other impacts, has a direct bearing on agricultural productivity. A reliable estimate of soil loss is critical for designing and implementing any mitigation measures. We applied the widely used Revised Universal Soil Loss Equation (RUSLE) in the Khabur River Basin (KhRB) within the NW part of the Zagros Fold and Thrust Belt (ZFTB). The areas such as the NW Zagros range, characterized by rugged topography, steep slope, high rainfall, and sparse vegetation, are most susceptible to soil erosion. We used the Digital Elevation Model (DEM) of the Shuttle Radar Topography Mission (SRTM), Tropical Rainfall Measuring Mission (TRMM), Harmonized World Soil Database (HWSD), and Landsat imagery to estimate annual soil loss using the RUSLE model. In addition, we estimated sediment yield (SY) at sub-basin scale, in the KhRB where a number of dams are planned, and where basic studies on soil erosion are lacking. Estimation of SY will be useful in mitigation of excessive sedimentation affecting dam performance and watershed management in this region. We determined the average annual soil loss and the SY in the KhRB to be 11.16 t.ha−1.y−1 and 57.79 t.ha−1.y−1, respectively. The rainfall and runoff erosivity (R factor), slope length (L factor), and slope steepness (S factor), are the three main factors controlling soil loss in the region. This is the first study to determine soil loss at the sub-basin scale along with identifying suitable locations for check dams to trap the sediment before it enters downstream reservoirs. The study provides valuable input data for design of the dams to prevent excessive siltation. This study also aims at offering a new approach in relating potential soil erosion to the actual erosion and hypsometric integrals.

Highlights

The classical Revised Universal Soil Loss Equation (RUSLE) model has been integrated with remote sensing and Geographic Information System (GIS) to estimate soil loss and sediment yield in the Khabur River Basin (KhRB)
Results show the spatial distribution and rate of average annual soil loss and sediment yield within selected basins that ranges from 0 t.ha−1 .y−1 to 3617.6 t.ha−1 .y−1, and from 6.9 t.y−1 to 165.12 t.y−1, respectively
Our study demonstrates that length and steepness factor (LS) and R are the most dominant factors controlling soil loss in the selected area

Summary

Introduction

Soil loss by water erosion is one of the most influential factors in land degradation, which cause significant environmental and socio-economic consequences that are critical to human welfare [1,2]. The evolution of the earth’s landscape results from interplay among three main factors, which are lithology, climate, and tectonics [3,4]. These factors control, directly or indirectly, the erosional rate and soil losses [5]. Geomorphological processes, including erosion, continually modify the landscape, reduce area relief, and generate a vast amount of sediment that directly impact agricultural, ecological, and water resources

Objectives

Methods

Results

Discussion

Conclusion