Green and grey infrastructures approaches in flood reduction

Abstract

This paper aims to advance the idea of sustainable flood reduction. Flood reduction through the use of the drainage system is considered an unsustainable approach that decreases the use of water. In contrast, the Water Sensitive City is a sustainable concept aimed at increasing the value of water for human needs and reduce flooding. The current approach of relying on drainage systems is ineffective and must be combined with green infrastructures to reduce flooding. Green infrastructures can increase infiltration rates or facilitate rain harvesting. The study developed four scenarios that combine green and grey infrastructures and used the Soil and Water Assessment Tool (SWAT) model to select the most effective scenario based on the remaining amount of flood volume in every scenario. Green infrastructures that are related to increased infiltration and rain-harvesting instruments reduced flooding by 22.3 and 27.7 per cent, respectively. Furthermore, a combination of the two types of green infrastructures reduced flooding up to 45.5 per cent. Conversely, applying only grey infrastructures (by increasing drainage capacity) to reduce the flooding to zero is unfeasible, as this requires more than double the current capacity. Therefore, a combination of green and grey infrastructures can significantly reduce flooding in a water sensitive and feasible manner. Applying a combination of green and grey infrastructures is a new and effective approach to reduce flooding in the Kedurus Catchment Area.