The role of catchment characteristics, sewer network, SWMM model parameters in urban catchment management based on stormwater flooding: modelling, sensitivity analysis, risk assessment

Abstract. Sustainable development of urban areas creates an increasing demand for computation tools supporting urban management strategies to mitigate the harmful impact of climate changes on the environment and quality of life, which would at the same time adapt coherently to the latest trends in architecture and urban planning. To date, hydrodynamic models of catchments have been used for this purpose. However, their application is limited due to the costs of model construction and problems with data acquisition. In this study an innovative algorithm for modelling specific flood volume is proposed, which can be applied to assess the need for stormwater network modernisation as well as for advanced flood risk assessment. In contrast to the currently used models, the approach adopted in this study includes characteristics of a catchment and of stormwater network, as well as calibrated model parameters expressing catchment retention and the conductivity of the stormwater network. In the proposed computation method, extended sensitivity analysis was conducted. Sensitivity coefficients of calibrated SWMM (Storm Water Management Model) model parameters were determined with regard to rainfall intensity, catchment and stormwater network characteristics. This extended sensitivity analysis enables an evaluation of the spatial variability of specific flood volume and sensitivity coefficients within a catchment, which is extremely important for identifying the most vulnerable areas threatened by flooding. This allows modernisation work to be focused on areas specifically susceptible to stormwater network failure. The measurement results for a catchment area in Kielce, Poland were used for the presentation of subsequent computation stages of the developed algorithm.

The presented computation method facilitates the management of urban catchments and water resources in urban areas, which can be applied at the stage of urban development planning and be used to inform decisions regarding modernisation and operation of stormwater networks. One of such examples is the demonstration of the reduction of the probability of system failure with the threshold of permissible roughness of sewage pipes. The adopted approach also helps to identify the key characteristics of catchment, stormwater network and SWMM model parameters, which have the highest impact on the functioning of a stormwater network, which is extremely relevant in terms of assessing and mitigating uncertainty in simulation results.