Mitigation of urban flooding: A simplified approach for distributed stormwater management practices selection and planning

Abstract

The urbanization process and the hydraulic insufficiency of drainage systems are two of the most common causes of urban flooding. In some technical regulations, distributed stormwater management practices (DSMPs) are regarded as a solution for urban flooding problems. They can prevent the formation of runoff, dispose of it locally, or dampen its peak before it reaches the drainage system. Due to their diffuse localization and the wide number of available solutions, the evaluation of their efficiency in terms of flood reduction is very difficult.

The methodology proposed in the present paper relies on the concept that the mitigation effects of DSMPs can be expressed as a function of the changes of the hydrological parameters of a catchment. Once the relation between a DSMP and the equivalent hydrological parameter is established, the efficiency of DSMPs can be evaluated using mathematical models simulating the runoff formation and propagation in urban areas and applying methodologies similar to parameter sensitivity analysis and model uncertainty propagation. Studying the effect of parameter variation on model output, it is possible to analyse quickly several different stormwater management solutions and to identify the best distribution of measures in order to achieve a defined mitigation task.

The simplified procedure has been compared with a more detailed approach obtained by fully integrate DSMPs in the drainage system hydrodynamic model. The procedure has been applied to the real case study of Mondello catchment in Palermo (Italy), and the analysis of the results allows the identification of some guidelines for the mitigation plan preparation.

Keywords:

• Best management practices
• Stormwater management
• Urban flooding

Acknowledgements

The authors would like to acknowledge the scientific support provided during the development of the present study by the RISURSIM (Σ! 2255) Research Group and, in particular, by SINTEF—Water and Wastewater (Trondheim, Norway) and Water Engineering Department at Norwegian University of Science and Technology (NTNU-IVB).