Assessing impacts of floods disaster on soil erosion risk based on the RUSLE-GloSEM approach in western Iran

Abstract

Floods cause great damage to ecosystems and are among the main agents of soil erosion. Given the importance of soils for the functioning of ecosystems and development and improvement of bio-economic conditions, the risk and rate of soil erosion was assessed using the RUSLE model in Iran’s Lorestan province before and after a period of major floods in late 2018 and early 2019. Furthermore, soil erosion was calculated for current and future conditions based on the Global Soil Erosion Modeling Database (GloSEM). Through the analysis of rainfall events, as the most important agent of soil erosion, the average R-factors for the period before and after flooding were 58.87 and 157.6 MJ mm ha− 1 h− 1 y− 1, respectively. The results showed that agricultural development and land use change are the main causes of land degradation in the southern and central parts of the study area. The impact of floods was also significant since our evaluations showed that soil erosion increased from 4.12 t ha− 1 yr− 1 before the floods to 10.93 t ha− 1 yr− 1 afterwards. Field surveys using 64 ground control points determined that erodibility varies from 0.17 to 0.49% in the study area. Orchards, farms, rangelands, and forests with moderate or low vegetation cover were the most vulnerable land uses to soil erosion. The results of GloSEM modeling revealed that climate change is the main cause of change in the rate of soil erosion. The results also established that when the combined effects of land use change and climate change are taken into account, soil erosion has increased under SSP1-RCP2.6, SSP2-RCP4.5, and SSP5-RCP8.5 scenarios, so that about 80% of the region has experienced moderate to very high erosion. Therefore, both natural factors (e.g. climate change) and human factors (e.g. agricultural development, population growth, and overgrazing) are among the drivers of soil erosion in the study area.