Jonas Schwaab successfully achieved his PhD dissertation on “Multi-objective optimization for improving the sustainability of urban development”
The goal of Jonas's PhD project was to show how results from multi-objective optimization can be used to improve the decision-making process concerning sustainable urban development in Switzerland.
Sustainable urban development in Switzerland involves the protection of fertile agricultural soils, which are under strong pressure. However, most of the fertile agricultural soils are often close to the existing urban settlements. Thus, there is a conflict between compact urban development and avoiding the construction of new urban sites on fertile agricultural land. To show how decision-making could be improved dealing with these two conflicting objectives, Jonas used results from multi-objective optimization.
A prerequisite for showing how decision-making can be improved, was to successfully employ multi-objective optimization and produce a so-called Pareto front. A Pareto front is a set of all solutions that are Pareto optimal, which means that they cannot be improved for one objective without accepting a loss in another objective. For producing a Pareto front of all the urban development patterns that were as compact as possible and at the same time had a minimal loss of the most fertile soils, Jonas employed the so-called non-dominated sorting genetic algorithm II (NSGA II). In order to make the algorithm more efficient for the problem of finding all optimal urban patterns, he modified the mutation process in the algorithm (further information can soon be found in a publication currently under review in the International Journal of Geographical Information science: “Improving the performance of Genetic Algorithms for spatial planning problems”).
After creating a Pareto front Jonas was able to show that the urban patterns obtained in the optimization process showed a significantly lower loss of agricultural soil quality than the urban patterns evolving through Business as Usual (BAU) urban development. In addition, he showed that there are some areas that can always be converted into urban areas, no matter whether it is preferred to reach the most compact urban pattern or the one with the lowest loss in soil quality (for further information please refer to Schwaab et al. (2017): Reducing the Loss of Agricultural Productivity due to Compact Urban Development in Municipalities of Switzerland). His results are not only relevant for decision-making processes in Switzerland, but could be relevant for many regions in the world and may even be important for decision-making processes other than the ones concerned with sustainable urban development.