1D/2D stormwater modelling to support urban flood risk management in estuarine areas: Hazard assessment in the Dafundo case study

Abstract

Flood risk management in urban areas adjacent to the coast is essential to increase their resilience. This study aims at improving scientific knowledge of flood risk alongside estuaries, considering different hazards and integrating estuarine and urban drainage modelling. Mathematical modelling of stormwater systems is a useful tool to evaluate the susceptibility to flooding and identify potential measures to reduce flood risk. The assessment of urban drainage flooding uses a coupled 1D/2D model, applying 1D model to the underground system and 2D model for the surface component. Assessment scenarios were based on variables rainfall, estuarine water level, and degree of obstruction in sewers and at system outfalls. Estuarine hydrodynamics were simulated using the SCHISM-WWM model. A web GIS platform was developed to support urban flood risk forecast and management providing urban analysis visualisation. The main objective is to forecast flooding in the Dafundo catchment supporting definition of population warnings. This paper proposes a flood risk assessment approach, using 1D/2D coupled modelling, estuarine hydrodynamics, integrating the assessment in a forecast web platform. The novelty is supporting an integrated flood risk management in stormwater systems, particularly in estuarine areas, providing an important improvement to assess flooding occurrence, regarding flood depth, area and duration. K E Y W O R D S estuary, flood modelling, flood risk assessment, integrated platform, urban drainage 1 | INTRODUCTION Urban areas adjacent to estuaries are particularly exposed to flood risks. Estuarine water levels often restrict the flow capacity of the urban drainage systems, a situation that can be significantly aggravated if occurrence of intense rainfall and high water levels in the estuary coincide. Severe conjoint conditions include high tidal levels together with storm surge episodes or with large freshwater discharges (Townend & Pethick, 2002). Rise in mean sea level as well as increasing frequency of extreme meteorological conditions (IPCC, 2013) are factors that

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