Natural flood protection: streamlining the planning of flood detention in natural landscapes for the reduction of urban flooding

A number of cost-effective and environmentally friendly flood reduction measures can provide detention of runoff from natural landscapes upstream of urban areas, with multiple added benefits. This study presents a methodology for assessing the needs for and feasibility of natural flood detention facilities. The candidate catchments for natural flood detention facilities were identified by GIS analysis and further assessed using data from maps and field inspections. Results for two case catchments show that a suitable topography and nature and biodiversity are key feasibility criteria for natural flood detention facilities. The study concluded that it is possible to streamline the process of selecting the location and type of natural flood detention facilities. Map analyses, field inspections and interdisciplinary collaboration are all important when planning natural flood detention facilities. As a result of the study, the City of Oslo will construct several natural flood detention facilities upstream of the city to gain practical experience with such facilities. While it is not expected that natural flood detention will solve all flooding problems in urban areas, it is expected that natural flood detention can positively contribute to future resilient stormwater management and the implementation of the EU Strategy on Adaptation to Climate Change.