Analysis of the impact of green infrastructure on surface runoff from urban areas

Abstract

Current construction methods and the marked increase in urbanisation are contributing to a high proportion of impermeable surfaces in built areas. Such surfaces reduce the infiltration of rainfall into the ground, which in turn leads to high amounts of surface runoff, which can have negative consequences in terms of flood safety. The introduction of green and hybrid infrastructure seeks to improve the characteristics of urban areas in terms of increasing the infiltration of rainwater and reducing stormwater runoff. In this study, we considered the larger industrial area of Rudnik in Ljubljana. Based on data on rainfall characteristics and soil properties, we calculated the surface runoff for the current situation and the situation when the improvements were introduced, where we took into account green roofs, tree planting and porous ground surfaces. Having analyzed the data, measurements, and calculations, we found that green infrastructure contributed positively to the reduction of surface runoff in urban areas, with differences of up to 20% at the annual level and up to 10% at the storm event level compared to the situation without improvements. In terms of surface runoff, the use of porous ground surfaces was identified as the best solution, with relatively small differences between the selected measures. From a financial point of view, tree planting was identified as the best solution, as trees can provide similar surface runoff reduction as green roofs and porous surfaces, with lower construction and maintenance costs.