Soil Erosion Modeling Using Satellite Rainfall Estimates

Abstract

This study attempts to assess the soil erosion of a Himalayan River Basin, Karnali and Nepal using the rainfall erosivity (R- factor) derived from satellite rainfall estimates (TRMM-3B42 V7). Average annual sediment yield was estimated using the well- known Universal Soil Loss Equation (USLE). The annual average rainfall erosivity factor (R) for the Karnali River basin over eight years was found to be 2620.84 MJ mm ha−1 h−1 yr−1. Using intensity-erosivity relationships and a dataset consisting of eight years of TRMM daily rainfall (1998-2005), the average annual soil erosion was also estimated for the Karnali River Basin. Maximum and minimum values of rainfall erosivity varied between 1108.7 and 4868.49 MJ mm ha-1 h-1 yr-1 during the assessment period. The average annual soil loss in the Karnali River basin was found to be 38.17 t ha-1 yr-1. Finally, the total basin area was categorized into the following erosion classes: slight (0 to 5 t ha-1yr-1); moderate (5 to 10 t ha-1yr-1); high (10 to 20 t ha-1yr-1); very high (20 to 40 t ha-1yr-1); Severe (40 to 80 t ha-1yr-1); and Very Severe (>80 t ha-1yr-1). Approximately 30.86% of the river basin area was found to be in the slight erosion class. Areas covered by moderate, high, very high, severe and very severe erosion potential zones accounted for 13.09%, 6.36%, 11.09%, 22.02% and 16.64% of the study area, respectively. This study revealed that approximately 69% of the Karnali River basin needs immediate attention from soil conservation analysts.