TOWARD CLIMATE CHANGE: Supply-Demand Assessment And Planning Response of Urban Green Space Ecosystem Service For Overland Flow Regulation In Bochum, Germany


2019
Ruhr-Universität, Bochum, Germany
Independent work, supervised by Prof. Harald Zepp
Proceedings of 4th International  Digital Landscape Architecture Conference

As a critical permeable landcover in the built environment, urban green space(UGS) can mitigate overland flow and decrease urban flooding risks. However, few studies have addressed the spatial disparity of the supply and demand for the overland-flow regulating ecosystem service(ORES).

In this research, an assessment framework was proposed to evaluate the demand, supply and budget of the ORES respectively based on the fine hydrological simulation of the pathways and catchments of overland-flows. The results of the disparity of supply and demand were illustrated using the method of Unit Hydrography.

The methodology was applied in the city Bochum, Germany and succeeded in identifying the areas with large demand meanwhile insufficient supply of ORES. With comparing the composition and the spatial distribution of UGS in each catchment, it was found out that approximately 40% of UGS was the threshold for a catchment to obtain enough service budget and that UGS sufficiently overlapping with overland-flow paths are able to provide ORES effectively. Some UGS development strategies and planning guidelines were consequently proposed to help practitioners arrange and allocate UGS efficiently.

Methodology Flowchart
Service Demand
Service Supply
Service Budget

Qk: Service Budget
Mk : Service Demand
Nk: Service Supply
k : Catchment k
Ak: Total area of Unit k
Ai : Total area of  non-green landcover in Unit k
Aj : Total area of  green landcover in Unit k
N: Precipitation of designed storm
Ψ: Runoff coefficient

           

Service Budget Relating to UGS Composition
Service budget in some catchments do not have a positive correlation with the UGS percentage and turn out to be unusually high or low. The downscaling analysis suggests that it could be due to the UGS composition. 
Service Budget Relating to UGS Spatial Distribution
UGS could contribute to the decreased waterlogging risk when it overlaps with overland flowpaths sufficiently meanwhile is evenly distributed along with their up- and downstream.
Service budget and social tradeoffs
Assign each catchment with a value according to their service budget and population density, respectively. Then identify four status by multiplying the assigned value, which leads to different development strategies.