Unit hydrograph synthesis for flood runoff design
Lowing, M. J.
PublisherUniversity of Lancaster
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The thesis is concerned with the development, for the United Kingdom, of a systematic procedure for the synthesis of a design flood hydrograph. The emphasis is on the large scale application of the unit hydrograph/losses model and a review of changes in concept relating to this technique is presented. Nearly 1500 events from 138 United Kingdom catchments are studied; after data screening, runoff volume is expressed as a percentage of rainfall and the unit hydrograph is derived for each event. Certain innovations in techniques of hydrograph analysis are described. The unit hydrograph is simplified to a triangle the shape of which is controlled by a single parameter, the time to peak. This time to peak and the percentage runoff are regressed on catchment and event characteristics. It is recommended that time to peak should be predicted in terms of catchment characteristics only; the single most important variable is main channel slope. The main variables in the prediction of percentage runoff are indices of soil type and antecedent catchment condition.