Effects of urbanization and climate change on surface runoff of the Brussels Capital Region: a case study using an urban soil-vegetation-atmosphere-transfer model

This study describes the use of a state-of-the-art urban parameterization (the Town Energy Balance scheme, TEB) to examine how the surface runoff of the Brussels Capital Region (BCR) responded to historical urbanization (1960-1999) and how it will respond in cases of climate changes and/or future urbanization. Key for this study is that both energy and water balances are resolved and interact through the evaporative term. Historical urbanization of BCR is estimated from changes in impervious surface area using remote sensing imagery and future climate is modelled using data from two members of the European project PRUDENCE. Results show that (1) a change could be detected in the annual series of cumulative surface runoff, high flow and the frequency of flood events when imperviousness exceeds 35%. (2) Climate change has a greater impact on low flows than urbanization. (3) In terms of high flow and annual cumulative runoff, historical urbanization and the precipitation increase scenario have approximately the same increasing trend. However, during summertime when floods happen frequently in the BCR, the average contribution of urbanization is four times greater than that due to the increase in precipitation in terms of the cumulative runoff ratio. (4) The assumed 10% increase in imperviousness in the BCR is able to counteract the increase in evapotranspiration due to warmer climate predictions. (5) When combining the effect of future urbanization (+20% of imperviousness) and precipitation scenario together, the increase in high flow is exacerbated. Copyright. (C) 2010 Royal Meteorological Society