ABSTRACT
Floods are regularly recurring natural disasters caused by extreme weather conditions, and in comparison with other natural disasters, floods can often cause tremendous economic damage and lead to environmental emergency situations that compromise the integrity of large infrastructures and the lives of many human beings. This is clearly evident in the recent devastation caused by Hurricane Katrina in 2006, when historic flooding affected not only the New Orleans area, but three coastal states in the USA. Over the last decade, Europe has experienced a number of unusually long-lasting rainfall events that resulted in severe floods – in the Netherlands, France and Germany (1993, 1995); the Czech Republic, Poland and Germany (1997); North Italy (1994, 2000); the UK (1998, 2000); and recently in Germany, Austria,
the Czech Republic, Slovalia, Russia, and Romania (2002, 2004). At the same time, Flanders has suffered repeated major flooding events (December 1993, January 1995, September 1998, and December 1999), and wide areas of the region were inundated causing significant damage to many essential infrastructures, as well as distress to the local population. Based on the increasing frequency and magnitude of flood events and responding to the above critical situation, the Flemish water administrations (Flanders Hydraulics Research (FHR) and Flemish Environmental Agency Water Department) encouraged several programmes for its flood management policy and to establish a preventive approach of flood protection. FHR has already developed several computer models of the most important streams to imitate the floods and to predict their geographical extent. This is done in online and offline mode. The offline study mode is used for scenario
calculations based on synthetic hydrographs while the online mode uses more than 400 rainfall, water level, velocity and discharge measuring stations sending values to the database with intervals between one minute and 60 minutes. To calibrate these models, an inundation database is provided with the models and contains the natural flooding areas (NOG) and the recently flooded areas (ROG) in Flanders from 1988 to 2005 (NOG/ROG data base). The database has been built up with information from local authorities, Flemish administrations and consultancy agencies. Also, the database is used as an important instrument for the policy of regional planning and the operational water system management. Statutory maps for the Watertoets (water test) or disaster insurance law are based on a combination of modelling results and the ROG database.
