An investigation in to the factors influencing flood magnitude in the British Isles
Existing methods used in the prediction of flood magnitudes likely to be experienced in British rivers are examined and reasons for prediction inaccuracies as well as problems of interpretation which may arise due to the use of multiple regression techniques, are discussed. Data from over five hundred river gauging stations in the British Isles are analysed in the development and calibration of a new causeeffect oriented rainfall-runoff model, and a new parameter is identified as representing the efficiency with which a catchment discharges its flood waters. Large errors and inconsistencies as well as a serious lack of range are found in the present soil classification system being used in Britain and improvements are suggested. A major new finding is that flood magnitudes generally increase in proportion to rainfall magnitude raised to a power of 1.3 and this relationship has now given considerable insight into the regional differences which have been observed in flood magnitude related to frequency of occurrence. Relationships describing the particular effects of the presence of lakes, urban development, and chalk areas, have also been obtained, and the thesis concludes with a survey of each region of the British Isles and examines any evidence of regional trends in floods behaviour and whether any abnormally large floods have been recorded in the past.
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