Floods are probably the most devastating natural disasters. Every year they cause considerable human and material loss. In China, for example, the Yangtze River overflowed its banks in 1998 to cause massive floods that swept away thousands of homes, necessitated the evacuation of tens of thousands of people, and led to thousands of human fatalities. Whilst the phenomenon in Belgium is less spectacular, floods are nevertheless true threats with which towns, villages, trailer parks, and camping areas located close to rivers and stream must reckon.

There is thus a fundamental need to mark out on maps regularly flooded areas to prevent people moving into them and constructing roads, buildings, and other infrastructure projects. Computer programmes that can simulate the effects of various types of river engineering (flood barriers, dams, holding ponds, etc.) on the location and extent of flooding are also a must.

When the ground is very wet it is much less permeable. That means that rainwater will soak into the ground less well and be more likely to run off into the rivers and streams, thereby increasing the flood risk. We must therefore be able to assess the soil moisture content as accurately as possible, since this serves as an alarm bell for the risk of flooding.

Finally, there is a crucial need to be able to evaluate the impact of climatic changes (warming, etc.) on the severity and frequency of flooding.