Determining the effect of slope length on soil erosion using the uncalibrated WEPP Hillslope model

This study investigated soil erosion on slope lengths of 22, 44, 66, and 88 meters located in the Ankara-Beytepe region. Soil loss and surface runoff data were observed on each slope from 1967 to 1996. The findings were compared with the uncalibrated WEPP (Water Erosion Prediction Project) model. The thesis study aimed to determine the effect of slope length on soil erosion. The results show that the lowest soil loss, observed and predicted by the model, was recorded on the 22 m slope. It's been observed that soil losses increase as slope length increases. The highest observed soil loss event occurred on the 44 m slope (0.215 kg/m²), while the highest soil loss predicted by the model occurred on the 88 m slope (0.187 kg/m²). The analysis of surface runoff data reveals that the highest surface runoff occurred on the 44 m and 66 m slopes, but decreased on the 88 m slope. The study aimed to determine the effect of slope length on soil erosion, revealing that the uncalibrated WEPP Hillslope model predicted soil losses more accurately than surface runoff. Given the arid climate of the study area, calibrating the model is essential to ensure reliable predictions of both soil loss and surface runoff. Calibrating the model for arid climates is crucial for improving prediction accuracy, as factors such as rainfall amount, intensity, evaporation rate, and soil moisture directly influence erosion and surface runoff.