Flood forecasting for the River Rhine in the Netherlands

The hydrological years 1994 and 1995 were characterized by two extraordinary extreme floods in the basins of the River Meuse and the River Rhine. Water levels were measured with return periods of more than 100 years, considerable damage occurred and as a precaution over 200 000 people had to be evacuated. Both events showed the importance of reliable forecasts with a sufficient forecast period. Until then forecasts for the Rhine River were carried out with a statistical model, allowing a reliable two-day forecast for the Lobith gauging station on the German/Dutch border. To extend this forecast period, a new flood forecasting model was developed. The first operational use of the new model during some minor floods at the beginning of 1999 showed reliable results for the three-day forecast and considerable improvement for the four-day forecast.