Sustainable runoff management using spatial modeling and multi-objective optimization

The rise in urbanization and the potential effects of climate change have increased the risk of flooding. Water Sensitive Planning (WSP) is a novel development approach combining regional and urban planning with water resources management. WSP aims to reduce stormwater's adverse effects, enhance potential hydrological ecosystem services, and treat stormwater as a resource rather than a hazard. This method considers various structural solutions (e.g., wetlands, permeable pavement, swales) to increase infiltration and water detention/retention.

These solutions need to be part of a regional-based strategy for maximum effectiveness. A spatial modeling tool can be used to simulate and quantify the effects of different solutions according to the characteristics of each place. The results of the simulation can then feed an optimization problem. This research aims to develop a holistic, simple-to-use methodology for surface runoff management by combining spatial modeling and multi-objective optimization. This methodology will be capable of considering various and sometimes conflicting hydrological, ecological, social, and economic goals.

We consider a realistic case study of the Tavor subbasin of the Jordan South watershed in Israel, using two different hydrological modeling tools: OpenNSPECT and SWAT. In the OpenNSPECT model, we divided the watershed into land parcels; then introduced a water detention-based solution to each parcel. We used the results to construct a Pareto optimum frontier to indicate the optimal placement for reducing runoff and sediment in key flood-sensitive areas. The SWAT model was used to compute annual average runoff and sediment. We then used this data as input for the systematic conservation software MARXAN to identify areas of an effective trade-off between hydrologic ecosystem services (runoff and sediment retention) and alternative land-use costs. We provide insight into the different solutions yielded by these two approaches and discuss the advantages, disadvantages, and possible future use.