THROUGHFLOW, OVERLAND FLOW AND EROSION

Abstract The Horton (1945) infiltration model of surface runoff and erosion is shown to be of much more limited geomorphic application than has been recognised hitherto. It is most applicable to clay badlands with low infiltration capacities and little weathered cover, and is one end-member of a wide spectrum of erosion models. The other end-member applies to slopes with high infiltration capacities and thick soil covers where throughflow dominates, and overland flow, with its attendant channel initiation, only occurs in a few restricted areas. Throughflow is capable of producing peaks in some river hydrographs, as is demonstrated both by controlled field experiments (Whipkey, 1965) and, by inference, by the “partial area” concept of runoff (Betson, 1964; Tennessee Valley Authority, 1963, 1964 and 1966). Experimental results of Hewlett (1961; Hewlett and Hibbert, 1963) are shown to be consistent with infiltration theory (Philip, 1957–8), indicating different response of throughflow to rainfall in the unsa...