Land degradation is one of the major global issues that affect agricultural output and natural resource availability (Gomiero 2016). Among the many forms of land degradation (soil truncation, loss of fertility, slope instability), soil erosion is the most significant phenomenon and is greatly influenced by land use and management practices (Abdulkareem et al. 2019). Erosion reduces the ability of the soil to hold water and support plant growth, thereby reducing its ability to support agro-biodiversity (Pimentel 2006). It is also believed that, as a result of the erosion over the past four decades, 30% of the world's arable land has lost its fertility (Hossain et al. 2020).
In recent years, climate change impacts have accelerated the rate of erosion and related consequences (Eekhout and De Vente 2020). Accelerated erosion can degrade the quality of land resources, leading to major environmental catastrophes (such as deposition, drought, and floods), impairing regional sustainability through detrimental ecological and social effects and having a significant impact on human survival and economic development (Lin et al. 2012). Soil erosion is a severe environmental concern in Nepal as well, with an estimated 25 ton ha− 1 yr− 1 national mean annual soil loss (Koirala et al. 2019). The rate and severity of the erosion also vary in different physiographic regions of the country, and approximately 45.5% of land erodes from the water in steeper areas of the hilly region (Chalise et al. 2019). Thus, studying soil erosion is crucial for scientifically predicting and controlling soil erosion as well as exploiting land resources(Pan and Wen 2014; Koirala et al. 2019).
In the Rangun Khola watershed of western Nepal, environmental hazards like landslides contribute to a higher rate of erosion and vice versa in the monsoon seasons (Bhandari et al. 2021). There have been a number of landslide events recorded over the last decades, leading to erosion (Pathak and Devkota 2022a). In this watershed, the natural elements, particularly the weather elements, are highly erosive (Dhital 2015). Because of the high intensity of monsoon rainfall over short periods of time, the erosivity of rain and run-off are major drivers of soil loosening, slope weakening, and finally mass movements of solid and semi-solid materials such as soil creep, landslips, and landslides (Koirala et al. 2019; Bhandari et al. 2021; Pathak and Devkota 2022b). Like many of the hilly areas that are on the way of being developed, this watershed is also in the growing phase of development. There are numerous such developmental activities such as the construction of roads and other linear infrastructure are found to be associated with higher amounts of erosion and associated hazards (Chalise et al. 2019). With the ongoing developmental activities and some other development projects in the pipeline for future developments, the risk of soil erosion and landslide events (Bhandari et al. 2021; Pathak and Devkota 2022a). As a result, the Rangun Khola watershed can be assumed to be under constant pressure for various agricultural and urban developments. In such a scenario, the quantitative information on soil erosion at the watershed scale is extremely useful in planning for soil conservation, erosion control, and watershed management(Pan and Wen 2014).
There are several models for analyzing soil erosion, but the most often used is the Universal Soil Loss Equation (USLE), which is an empirical model assessing long-term averages of sheet and rill erosion based on plot data gathered in the eastern United States (Morgan et al. 1998). Other models used to assess soil loss include the Erosion/Productivity Impact Calculator (Williams 1990), the European Soil Erosion Model (Morgan et al. 1998), and the Water Erosion Prediction Project (Flanagan and Nearing 1995). The Revised Universal Soil Loss Equation (RUSLE) was created as a result of substantial improvements to the USLE as well as its database in order to more correctly assess soil erosion (Renard et al. 2017).
The RUSLE with GIS is employed in this research to assess the soil erosion potential, which is one of the major environmental problems in the Rangun Khola watershed. Along with this association, another equally significant and related environmental concern landslides, was carried out, which directly impacts and is influenced by soil erosion. It is anticipated that the findings of the study would give planners and decision-makers crucial information they may use to develop effective land management plans in the watershed.