Overall resistance parameter of flow arising in the catchment-area of a reservoir in steep land

On a small reservoir catchment in mountains, the basin storage S(t) during a flood was expressed in terms of the basin discharge Q(t) and the time-varying storage parameters K(t) and P(t), in a storage equation S(t) = K(t) Q(t)^P(t). Applying a nonlinear filtering technique to identification of the dynamic variations of the time-varying storage parameter P(t), the overall resistance law of flow in the catchment was estimated. The results showed that variations of the time-varying storage parameter were closely related to the generation of fast flow on the catchment, represented by gully runoff, and that P(t)-values of 0.4 and 1.0 corresponded to the generation of overland flow described by Manning's formula and to subsurface stormflow described by Darcy's equation.