Assessment of land use change in the thames catchment and its effect on the flood regime of the river

Land use changes over a 30 year period (1961–1990) have been incorporated into a continuous simulation rainfall runoff model to investigate the effect of these changes on flood frequency in the Thames catchment to its tidal limit at Kingston. The base map of land use in the Thames catchment uses a 50m grid of 25 land use classes for 1990. For use in the rainfall runoff model these classes have been combined into six land use types. Statistics of percentage change for four land use categories, cultivated land, permanent grassland, woodland and urban areas, are available back to 1945, calculated every five years. These statistics are at a county level and were related to the six land use types used in the rainfall runoff model to assess the flood frequency changes in the Thames catchment in relation to land use. Broad scale changes in land use over the last 120 years in the Thames catchment were also determined from a variety of sources.