Field applications of a variable-parameter Muskingum method

This study demonstrates field applications of a physically based variable-parameter Muskingum method for routing floods using daily and two hourly flood data available for six reaches of three Australian rivers and using hourly flood data available for a specified stream-network segment of the Tyne River in the United Kingdom. Some of the flood events studied for Australian rivers inundated the floodplain. The study illustrates how to estimate the routing parameters at every routing time interval using limited channel cross section data, and the wave speed-discharge relationship developed for the routing reach; this can be derived from past observed flood hydrographs or the rating curves available at the inlet and outlet of the study reach. Overbank floods are routed through a two-stage rectangular compound cross section channel, and the method used to determine the floodplain width on the basis of the applicability criterion of the method is described. The major advantage of the routing approach followed in the study is that no information on channel roughness and no calibration are required to estimate the parameters. The ability of the method to reproduce the observed flood hydrographs is evaluated using the Nash-Sutcliffe criterion. The results of the field studies reveal the appropriateness of the method for practical flood routing in river channels.