Author(s): Eduardo Garcia; Beatriz Tejerina; Luis Carlos Lorenzo; Manuel Del Jesus; Cesar Alvarez
Linked Author(s): Manuel del Jesus, Beatriz Tejerina Vega
Keywords: Nature-based solutions (NBS) Sustainable Urban Drainage Systems Sponge City Cost-benefit analysis of urban drainage systems Effectiveness of NBS
Abstract: NBS encompass a wide range of technologies and infrastructures that are gaining traction in urban water management, usually as a complement to standard drainage systems. Although NBS have been tested in many cities, there is still resistance to their use, especially in developing countries, often citing high costs (both construction and maintenance), the need for large urban areas, and uncertainty about their flood mitigation effects. This paper provides a methodological framework and associated open-source numerical software to quantify the combined effect of a package of NBS (including several typologies) on a given city, in terms of reduction of peak discharges associated with a given return period. The method is intended for scoping and pre-feasibility analyses and avoids detailed modeling of each infrastructure (which requires its exact location and characteristics) by extracting key urban features from the affected areas and introducing reasonable, expert-based implementation ratios for each type of NBS. These implementation ratios depend on local conditions and can be obtained using a combination of coarse flood hazard modeling (based on global DEMs and aerial imagery as provided by Google Earth or equivalent). A simple, event-based hydrological model is then used to translate the effect of the proposed NBS package into a reduction in peak flows. The hydrological model also includes a representation of the upper catchment in a lumped way and differentiated from the lower catchment (which is assumed to host all NBS), allowing the simulation of complementary measures in the tributary area, such as retention basins and changes in land use/land cover. Peak flows, as they come or after some transformation, can be considered as a proxy for risk, and therefore provide a first estimate of avoided damages, which can be used for a basic cost-benefit analysis.
Year: 2025