Land use and damaging hydrological events temporal changes in the Sarno River basin: potential for green technologies mitigation by remote sensing analysis

Abstract

The urban growth leads cities to adopt sustainable strategies in order to mitigate the relevant hydrological effects. In this study, the use of synthetic aperture radar SAR imagery has allowed us to demonstrate a 70% increase of the built-up area in Sarno River basin between 1995 and 2016. This increase is linked to the statistical temporal increase of the damaging hydrological events occurring during the same period. To restore the pre-development hydrological condition, a scenario analysis was undertaken where SWMM was used to simulate the hydrological effect of green roof retrofitting landscape design. SAR imagery was furthermore used to explore the potential retrofitting surfaces, leading to defining three different conversion scenarios with 5%, 30% and 100% of potential retrofitting surfaces. The study demonstrated that the pre-development hydrological condition can be never fully restored. Indeed, this scenario is partially equaled only by a 100% green conversion of the existing traditional roofs, with average runoff and peak flow reduction of 41% and 25%, respectively. Such conditions are clearly not feasible, provided the obvious retrofitting limitation for existing buildings. The use of additional nature-based techniques, beyond green roofs conversion, should be explored in the perspective of a balance for urban growth.