Assessing the Benefits of Nature-Based Solutions in a Storm Drainage System – a Case Study

In most developing countries, stormwater drainage practice consists of a conventional storm drainage system designed to collect and convey excess runoff to the recipient as soon as possible, without any attenuation or peak flow decreasing effects. This paper aims to show the overall need for change in the urban drainage paradigm by showing the effects of reconstruction of the existing conventional stormwater drainage system into a new one by including green elements. Part of the existing system is replaced with vegetated swales, and two detention ponds are added in the common green areas (parks). Effects are analysed through a comparison of results from a mathematical rainfall-runoff model for the existing and reconstructed stormwater drainage system for both water quality and quantity at the sub-basin outlet point. The cost-effectiveness of the applied measures is quantified by comparing construction prices for the existing and the reconstructed system. The obtained results clearly show an urgent need for stormwater drainage practice improvement in countries where the conventional approach is still in use.