Model shows where in Brussels extra green space can be provided to cope with drought and flooding
Among the effects of global warming, increased drought, a higher risk of flooding and sewage water flowing directly into rivers after heavy rain are particularly challenging for cities. There is often little undeveloped space where that water can be collected and stored in nature. The WETSPA-Urban model developed by Dr Nahad Helmi for his doctorate in engineering at the Vrije Universiteit Brussel is helping cities to carry out cost-benefit analyses of possible precautionary measures, such as more green space, and shows the areas where these are best implemented.
“The model mainly helps to identify appropriate locations for green infrastructure in cities, such as green roofs, rain gardens, green streets, etc, where more water can infiltrate or be stored. The model can support water quality management, flood planning or drought planning. These nature-based solutions also have positive effects on the wellbeing of city residents: for example through heat islands that can be reduced in this way,” explains professor of hydrology Ann van Griensven, who supervised the research as promoter.
Brussels as a test case
The WETSPA-Urban model (Water and Energy Transfer between Soil, Plants and Atmosphere) was developed within VUB’s hydrology research group and combines data on natural runoff with simulations of urban drainage for sewers and a hydrologically detailed infiltration model. The tool made maps with recommendations. The simulations with these recommendations show that a smart application of green infrastructure has a large positive impact, especially with smaller, more frequent floods. In the PhD, the model is applied to Roodebeek in Brussels. By applying low-impact development to 16% of the Roodebeek sub-basin, one of the most urbanised parts of the Woluwe sub-basin, flooding can be reduced by 85%.
Van Griensven: “Preventing floods also has an impact on the drought that we are now facing – because green infrastructure helps water to infiltrate or be stored for use later, for example for urban agriculture.”
The PhD will now be continued in the form of an innovation mandate (VLAIO). Within this framework, the research group will also collaborate with Aquafin on a new test case in Tervuren.