U.S.- Italy Research Workshop on the

Hydrometeorology, Impacts, and Management of Extreme Floods

Perugia (Italy), November 1995

CHANGES ON FLOOD CHARACTERISTICS DUE TO LAND USE CHANGES IN A RIVER BASIN

G.A. Schultz

Institute of Hydrology,Water Resources

Management and Environmental Techniques

Ruhr University Bochum

44780 Bochum, Germany

Recent extreme flood events in the center of Europe caused public discussion on the question whether more frequent and more severe floods and conditions for flooding are getting more severe and the extent to which they are at least partially man-made. This paper presents a research project, in which the impact of the land use changes on flood hydrographs is investigated. A distributed rainfall-runoff model, which parameters are determined on the basis of satellite imagery, digital terrain models, and digital maps, is developed and its validity is demonstrated for a subcatchment within the international Mosel river basin. Two types of land use changes are investigated: the increased urbanization and forest disease leading to large scale forest death. Two scenarios are considered for the test catchment: a) the urbanized area is significantly increased and b) all trees above 400 masl are assumed to be dead. It is shown how such land use changes can be generated on maps and how the parameters of the hydrological model change according to such land use changes. For a selected historical flood the impact of the changes on the flood hydrograph are presented. In both cases a) and b) flood conditions became more severe, i.e. the rising limb becomes more steep, the peak considerably higher, and the flood volume significantly larger. In conclusion both types of land use changes produce a significant deterioration of flood conditions.