“In fact, a map of the flood-risk areas in Wallonia already exists”, explains Michel Pirotton, an associate professor of hydraulics at the HECE unit. “We extended the methodology to cover stronger occurrences. Different stages of calculations and hydraulic modeling are required in order to determine the vulnerability of a flood-risk area. For areas near the river, we used a hydraulic model with a five meters by five mesh. We simulated the flow of water on digital mockups of towns where we simulated the overbank flooding of the river Meuse. Every five meters, we obtained a value for the height of the water, the speed of the flow in each direction and then, by crossing the model with other data, the damage inflicted”. These measures were also useful for studying those undeveloped ares that the authorities consider suitable for development.

Establishing a precise mapping of the areas vulnerable to flooding was of the utmost importance in order to envisage a better management of dams, but especially, to assess the relevance of more restrictive political measures with regard to construction in flood-risk areas. These measures will have to take account of a large increase in urbanization, because by the year 2100, there will be 700,000 extra dwellings in Wallonia, and this does not include future industrial zones, new schools, businesses and road and rail networks. Given such growth, and in-keeping with current growth, all the areas proposed in the development plan, including high-risk areas, will probably be occupied by the end of the century. Given this fact, there are two possibilities to be considered.  New construction zones will have to be found, or, more realistically, population density in urban areas will have to increase. 

Nine possible urban scenarios

Urbanization is not something that takes place without due consideration, it must follow certain trends such as ecological awareness, economic development, the cost of land for development, or the concentration of areas of major employment. Based on recent knowledge of the degree of risk associated with vulnerable areas, together with the socioeconomic questions mentioned above, the researchers have developed nine possible urbanization scenarios and have calulated a damage estimate due to overflowing of the river Meuse. 

There are three possible ways in which urbanization might develop. Firstly, the development might take the form of the current trend, by following the development plan envisaged by the government of Wallonia in the 1980s to organize urban planning in the region.“However, at a time when there were few problems such as traffic jams, public transport, and sewer networks, urban planning was organized in the form of a very extensive network in areas where current dwellings are concentrated and left a lot of space available for future urban development. Today, urbanization is very spread out and could be unfavorable in terms of the vulnerability of areas to flooding.”, explains Arnaud Beckers.