Discussion on Design of flood synthesis by excess rain routing . Index to Volume 17 1975

Trials of several routing procedures for hydrograph synthesis revealed that routing of the excess rain hyetograph through a single linear reservoir-type storage could yield a plausible direct runoff hydrograph provided the shape and drainage pattern of the catchment was not abnormal. The method requires evaluation of only one parameter, the routing constant K to define the hydrograph for an excess rain of given depth and duration. K values were determined for 92 South African catchments by seeking best-fits between routed and observedunitgraphs. To aid estimation of K for ungauged catchments the country was subdivided into veld-type zones for each of which a relationship between K and area of catchment was provided. A worked example demonstrated the method.