EXPERIMENTAL STUDY OF OVERLAND FLOW USING ADVANCED HYDROLOGIC SYSTEM

Abstract

This experiment studies was conducted to understand overland flow behavior on the V-catchment placed on the Advanced Hydrologic System for different overland and channel surface roughness, slope and rainfall intensities. The overland flow slope was varied between 0.0011 % to 0.022 % and the channel slope varied between 0.0005 and 0.005 . The rainfall intensity was varied between 36 mm/hr to 84 mm/hr. Considering different combinations of flow simulation scenarios, a total of 135 laboratory experiments were conducted on three types of overland flow plane and channel roughness conditions i.e., flow planes composed of acrylic sheet, and flow planes with artificially introduces roughness with the help of two different grades of sand papers pasted on the acrylic V-catchment. The kinematic wave approximation based overland flow model was used for simulate the observed hydrograph. The resistance to overland flow in terms of Manning n was evaluated by using hydrograph fitting technique. For acrylic sheet based overland and channel flow configuration of the experimental setup, the Manning's n varied between 0.012 and 0.017. Similarly for overland flow planes and channel planes lined with sand paper, the fitted value of Manning's n was found in the range 0.0 14 to 0.02. In general, when rain intensity is higher, the Manning's roughness coefficient also increases. Overall it was found that the kinematic wave approximation based overland flow model is able to reproduce the observed hydrograph in most of the cases with Nash-Sutcliffe Efficiency more than 95%.