301 - Separating Infiltration and Runoff from Precipitation over Anacostia River Watershed, Maryland

One of the most important environmental problems is rainfall-induced landslides that have increased due to climate change and heavy rainfall. In most of the previous landslide studies, researchers often resort to simplifications, such as assuming that all precipitation effectively infiltrates into the ground or approximating the infiltration amount as a fixed percentage of the total rainfall, regardless of how these approximations can lead to inaccurate results and outcomes. By understanding how much rainfall infiltrates the ground, researchers gain insight into the amount of water that can potentially saturate the soil on the slope, triggering landslides. To address this challenge, our study utilized the Richards-equation-based SWAT model (RSWAT) to simulate the intricate interplay among rainfall, surface runoff, and infiltration over the slopes. This model was applied from 2012 to 2022 in the Anacostia River watershed in Maryland, US, as a case study to separate the amounts of runoff and infiltration from rainfall. We used Pbias and R2 to evaluate the model performance. The results show the acceptable accuracy of the model in rainfall-runoff simulation and engineers and managers can use this model to better estimate amount of infiltration from rainfall as a threshold in the risk assessment of future rainfall-induced landslides.