In July 1997 two episodes of heavy rainfall in the upper catchment of the Odra river caused severe flooding in the Czech Republic, Poland and some areas of Germany. Hundreds of cities and villages were inundated, more than 100 casualties occured and vast areas of land were flooded for weeks. In such a critical flood situation quantitative predictions of water levels and discharges are required as well as a set of rules for the intelligent control of weirs and polders and the resulting impact of the river flow.

The ODRAFLOOD project develops a multi-scale system of coupled hydrological models that meets various demands of a comprehensive flood forecasting and warning system. The structure of the system refers to the chain of processes converting extreme rainfall and/or snow melt into runoff and river discharge, transforming the flood waves downstream, and inundating local areas.

The rainfall-runoff relationship is simulated with the land-surface scheme SEWAB (Surface Energy and Water Balance) which is applied to the whole Odra basin on grids of 7x7 km size. The excess water is routed through the river channel network by a horizontal routing scheme which is calibrated with respect to subcatchments. Forcing data from 50 synoptic stations and 1250 precipitation stations are used to force the model. Daily discharges of 29 gauging stations are used to calibrate and verify the model.

Alternatively, the wave transformation in the upper and middle Odra river is simulated with the operational IMGW hydrodynamic model. In the lower Odra, flow conditions are much more complex because various types of polders and weirs, tailbacks, wind effects and lateral flows in the channel network of the estuary. These effects are simulated by the MRI hydrodynamic model.

Like a magnifier to the MRI model, the two dimensional model TRIM simulates transient heavy lateral flows and tailbacks on the main river. The complex and small-scale morphology of buildings and terrain determines the inundation of urban areas. High-resolution elevetation modles are generated for the cities of Wroclaw and Frankfrut/Oder. Inundation scenarios are simulated with the dynamical-statistical model ARCHE of DLR.

Results of off-line simulations of all model components will be presented for the Odra flood event in 1997.