GIS-Based Estimation of Soil Loss from Hilly Urban Area Incorporating Hill Cut Factor into RUSLE

Unplanned residential development in hilly areas leads to steep cuts in natural hillslopes, which in turn, results in excessive soil loss. GIS-based Revised Universal Soil Loss Equation (RUSLE), applied in such a case, underestimates soil loss since such near vertical surfaces are not completely projected in orthorectified satellite images. This paper introduces a "hill cut factor (H_f)", which is input into the cover management factor of RUSLE model. Model is validated with observed soil loss data of a mini hilly urban watershed located in Japorigog hill of Guwahati city. GIS-based soil loss estimation has been carried out for two scenarios: with and without consideration of H_f. Results reveal that consideration of H_f in GIS-based RUSLE replicates the picture of erosion more accurately and gives a similar result with observed soil loss data. Without consideration of H_f, RUSLE underestimates annual soil loss from the studied watershed by almost 28% than the observed value. Adequate design of drainage system by using more accurate soil loss information, derived in this way, can lower the urban flood problem caused due to blockage of drains and culverts with sediments brought down from the inhabited hills in a city.