Evaluation of the impact of land use ratios and cover materials in settlement design on stormwater runoff

Due to higher levels of urbanization and increasing impermeable hard land covers, green spaces are decreasing, resulting in stormwater loss as surface runoff instead of being absorbed by soil and reintroduced into the water cycle. This study investigates the effect of land use ratios and land cover materials resulting from settlement design on surface runoff volume. The study was conducted using various scenarios in 9 settlements with different land use ratios, including roofs, sidewalks, parking areas, roadways, and green areas in Istanbul, a city with a high urbanization rate. Thus, surface runoff volume in settlements depending on the land use ratios was evaluated. A total of 336 material combinations were developed using various material alternatives in addition to different land use ratios. Therefore, the effect of different land cover materials used in the settlements on surface runoff volume was also evaluated. Study requirements were taken into consideration when choosing the calculation method, and the Rational Method, often preferred for calculating surface runoff volumes in small urban basins, was chosen. According to the calculation results obtained from the settlements developed for this study, surface runoff volume can be reduced by 37.10 % by increasing only the green space ratio and by 67.65 % by using different material alternatives in the same settlement. Additionally, it was observed that each improvement made to reduce surface runoff in settlements resulted in a positive change.