Integrating residential microsimulation, land-cover change modelling and urban planning scenarios to explore alternative futures: a case-study on Brussels

Traffic congestion and urban sprawl are pervasive in the regions of Flanders and Brussels, causing damage to health, economy and nature. Due to the severity of the situation, urban densification strategies, aimed at reducing future land take, have recently become an important topic of public debate in Belgium. At present, there is still much uncertainty regarding the possible impact of proposed policy measures, or lack thereof, on future residential patterns and on the physical urban environment. Such information is key however to (1) assess alternative policy proposals and (2) to develop implementation strategies on various levels of governance once a regional plan has been approved. For our case-study, we designed 2 contrasting urban planning scenarios, called Business As Usual (BAU) and Sustainable development (SUS), for Brussels and the province of Flemish Brabant. BAU represents a status quo scenario whereas SUS aims for considerable yet achievable densification around public transport and service hubs. A spatial microsimulation framework is proposed to simulate residential dynamics of different household segments up to 2040 for both scenarios. This information is in turn combined with economic projections to define local demand for surface sealing, an important measure for many urban ecosystem service indicators. All projections are produced on census tract level. Finally, a quantitative state Cellular Automata modelling framework is used to simulate changes in impervious surface cover at the level of 30m cells. All models are validated for the timeframe between the last Belgian Censuses of 2001 and 2011. The research shows how integrated modelling approaches combined with transparent scenario analysis can contribute to a better-informed debate on sustainable urban development.