This thesis is concerned with the study of flood plains and the flood hazard in England and Wales. Flood plains form an important resource which is only successfully utilised by the reduction of the flood hazard. The extent of the flood hazard in a study area, the problem of assessing flood damage, and the perception of the flood hazard and adjustment to it, are all investigated in order to suggest ways in which floods may be reduced. The flood hazard is a widespread phenomenon affecting most parts of the study area of this dissertation which consists of the Severn, Wye and Usk catchments, and a group of catchments in Glamorgan. Most major settlements extend into flood risk areas, and require flood alleviation programmes. Flood damage assessment is found to be a major problem which adversely affects our ability to optimise flood plain resource use. The assessment of potential flood damages based directly upon actual damage data is found to be impracticable. Instead, standard flood damage information, based upon actual flood damage data, is developed for residences. This allows the computation of potential residential flood damage. The important problem of flood hazard adjustment is considered in a study of the preconditions of flood hazard perception and individual and community adjustment at study sites. The adjustment process is found to be conditioned by flood experience, spatial variations in the hazard, access to information and adjustment evaluation, whilst personality traits do not appear to be directly important. At the community level, unconventional combinations of adjustment are found to be of value, although low levels of public awareness of flood risk pose a serious problem. Flood hazard reduction can be improved in this country by explicit management of flood plains, by improved economic analyses, and by the application of behavioural principles.