Determination of Nonlinear Functional Response Functions in Rainfall‐Runoff Processes

The operation of some hydrologie systems can be represented by a functional series expansion involving higher order nonlinear generalizations of the convolution integral, which underlies the unit hydrograph concept. A method was developed to determine the linear and nonlinear response functions of such systems on the basis of concurrent records of the input and output. This procedure was successfully tested in a special laboratory catchment and in a natural watershed to establish rainfall‐runoff relations.