Prioritization of Surface Runoff Management Scenarios Using TOPSIS Method in Different Weighting Conditions (Case Study: Bojnord City)

In the past decades, urban development and the increase in densely populated urban areas have led to expansion of the impervious surfaces. This resulted in an increase in the volume and peak discharge of runoff. To face the intensified urban floods problems worldwide, many management practices have been proposed and implemented. This study attempted to investigate and prioritize suitable urban runoff management scenarios for Bojnord city. Based on a thorough literature review on international experiences and examples, local experts’ opinions, and operational feasibility, a total of six management alternatives including Bio-retention, Infiltration Trench, Pervious Asphalt, Pervious Paver Blocks, Green Roof, and Rain Barrels were chosen. The hydrological, social and economic implications were then assessed for these alternatives for the Bojnord city. A total of 60 questionnaires were filled out by face to face interviews with citizens. Likewise, an extra set of 30 questionnaires was filled out by the relevant experts and authorities. The cost of each management alternative along with their potential to reduce the runoff volume resulting from a rainfall with a five-year return period was analyzed using SWMM. The Multi Criteria Decision Making Method (MCDM) was used for prioritizing these alternatives. Then MCDM in this study used TOPSIS technics and was performed using different weighting conditions (equal weighting, Delphi, Shannon entropy, emphasizing on hydrologic, social and economic criteria).The result of this study indicated that when applying equal weighting method, Delphi and social criteria, Infiltration Trench scenario were considered as the most compatible option to ideal solution. While Rain Barrels scenario was considered as the top priority when Shannon entropy and economic criteria were emphasized. And finally, applying a hydrologic criterion put the Green Roof scenario on top priority