Saturation excess surface runoff
From HydroWiki
Surface runoff generated by saturation excess mechanism. The condition of runoff generation is (1) Permeability of soils in the upper zone is higher than that in the lower zone; (2) Water content of the upper zone reaches the saturated water storage. (Reference:Rui, X.F.,2004. Principles of Hydrology,. Chinese Waterpower Press, Beijing, China.p147.)
