Relationship between drought and soil erosion based on the normalized differential water index (NDWI) and revised universal soil loss equation (RUSLE) model

The Langat River Basin in Malaysia is vulnerable to soil erosion risks because of its exposure to intensive land use activities and its topography, which primarily consists of steep slopes and mountainous areas. Furthermore, climate change frequently exposes this basin to drought, which negatively affects soil and water conservation. However, recent studies have rarely shown how soil reacts to drought, such as soil erosion. Therefore, the purpose of this study is to evaluate the relationship between drought and soil erosion in the Langat River Basin. We analyzed drought indices using Landsat 8 satellite images in November 2021, and created the normalized differential water index (NDWI) via Landsat 8 data to produce a drought map. We used the revised universal soil loss equation (RUSLE) model to predict soil erosion. We verified an association between the NDWI and soil erosion data using a correlation analysis. The results revealed that the southern and northern regions of the study area experienced drought events. We predicted an average annual soil erosion of approximately 58.11 t/(hm 2 •a). Analysis of the association between the NDWI and soil erosion revealed a strong positive correlation, with a Pearson correlation coefficient of 0.86. We assumed that the slope length and steepness factor was the primary contributor to soil erosion in the study area. As a result, these findings can help authorities plan effective measures to reduce the impacts of drought and soil erosion in the future.