PhD project: Climate change and future of green infrastructure from roof to city scale

Besides the social challenge, stormwater management must face climate change. Several studies have made forecasts of future performance of green infrastructure by considering different scenario of climate change. However, until recently the spatial and temporal scale of regional and local climate models have not been sufficient to accurately evaluate future performance in a temporal resolution that is usable for urban stormwater management. Previous studies centered on climate change on a regional level based on downscaled global models, and some studies have attempted to understand how different green infrastructure interact at the city scale. However, there is still a lack of understanding about how both social aspects, climate change, and scale shift will coexist in the future.

The main question of Vincent Pons’s PhD project will be, considering current knowledge and orientation in the use of green infrastructure, the assessment of future performance of these green infrastructures. In a way to study various conditions the study will be centered on two urban areas; Trondheim (Norway) and Lyon (France), with different climate, urban morphology, social environment and decision-making process. Green infrastructures (GI) studied in this PhD will start from roof scale, green roof with considerations for raingardens and other GIs, up to the to city scale. Climate change scenarios in this study will be based on climate change data downscaled to a locally adapted urban temporal and spatial scale. As social aspect will more and more be included in future urbanization projects and that perfectly optimized placement implementation will be subject to uncertainty, scenarios of green infrastructure implementation and location will be developed with regard to social integration in order to measure hydrological performances of a city under different decision-making dynamics. Hydrological performances will be considered toward time series to consider both daily and annual performances (long-term) and event-based simulation to assess about performances under extreme rain. This study will have to deal with uncertainty in performance forecast while insuring low algorithmic complexity link to the use of city scale model in order to compute different scenarios.

Study objectives The main objective of this PhD is to push the boundaries of today’s knowledge about the hydrological performance of Green Stormwater Infrastructures (GI) in a future climate, as individual units and as integrated systems within urban catchment. The focus will be on modelling the systems on different spatial scales; from individual units to city scales. Specific objectives are as follow:

1. To better understand GI’s performance under future climate, different locations and different scales
   To quantify and estimate change in performance (retention and detention) of GIs according to climate change and based on physical-based model and climate change scenario. Understanding better the performance of GI at different scales (from individual units to city scale).

2. Evaluating hydrological response of GIs implemented at city scale according to different policies
   Different scenario of implementation according to multi-purpose (including environmental aspect and social integration) according to local conditions. The aim is to identify feasible association of GIs according to urbanization trend and fully integrated GIs.

3. Assess performance at city scale with reasonable algorithmic complexity
   Recommend methods to achieve reasonable balance between uncertainty and computational cost. This method should be usable as a tool for multiple criteria decision analysis and design purpose.

The supervisor team is Tone Merete Muthanna (Pr. NTNU, Norway), Jean-Luc Bertrand-Krajewski (Pr. INSA de Lyon – Deep, France) and Edvard Sivertsen (research scientist at SINTEF community)