Critical Source Area and Minimum Source Channel Length Effects On Eventflow and Sediment Loadings.

The spatial discretization scale determines the degree to which the spatial heterogeneity of the surface condition and the stream network can be represented. It has been recognized that discretization scale significantly affects watershed model results, with respect to both hydrology and water quality.  Due to the effect of channel storage and transport capacity, the event flows tend to attenuate and delay with decrease in the critical source area (CSA).  While, sediment delivery ratio decreases as cell size increases, indicating a smaller amount of sediment delivered to outlet, transport capacity increases as cell size increase, indicating that a large amount of sediment could be transported downstream. This study emphasizes the combined effect of CSA and minimum source channel length (MSCL) on stream flow and the sediment load at watershed outlets. Comparisons were made between combined CSA and MSCL with topographic parameters (i.e. average cell slope, average channel slope and the length to width ratio) of each watershed. Correlation of topographic parameters with normalized differences of stream flow and sediment load revealed the effect of CSA and MSCL in event flow and sediment load estimation.