Developing a GIS tool for emergency urban cooling in case of heat-waves

Abstract

Many cities are expected to face a strong increase in the frequency and intensity of heat-waves by the end of the 21st Century due to climate change. In Paris, the frequency of heat-waves could rise from an average of one day per year to 14–26 days per year, with temperatures reaching up to 50 °C. Since 2012, pavement-watering is viewed as a potential tool for emergency cooling by the city while scientific work on the technique has found its application to be best suited to densely built urban areas, compared for example to urban greening whose impact may be hindered by lack of available planting space.This paper proposes an interdisciplinary approach combining urban physics with social sciences to develop such a GIS model for pavement-watering as an emergency response to heat-waves in Paris. It is built on performance criteria derived from previous work are input into a Geographic Information System to identify urban areas where pavement-watering would be most effective. In addition, a heat-related health risk assessment is conducted, using microclimatic, urban and socio-economic layers, to single out areas where heat-wave risk is highest in public spaces, combining high temperatures, pedestrian traffic and local population vulnerability. The microclimatic hazard dataset includes a physical model of park and water body cool islands assuming they are driven by thermal diffusion.The resulting tool has significant flexibility in defining the thresholds of the different indicators. The mapping scheme identified a total of 50 to 200 km of high priority areas for pavement-watering, requiring between 1400 and 5800 m3/day of non-potable water, equivalent to 0.6 to 2.6 L/day per capita. Limitations due to data quality or resolution are discussed as well as paths for further improvement.