Abstract:
Pluvial or surface flooding can cause significant damage and disruption as it often affects highly
urbanised areas. Therefore it is essential to accurately identify consequences and assess the risks
associated with such phenomena. The aim of this study is to present the results and investigate the
applicability of a qualitative flood risk assessment methodology in urban areas. This methodology
benefits from recent developments in urban flood modelling, such as the dual-drainage modelling
concept, namely one-dimensional automatic overland flow network delineation tools (e.g. AOFD) and
1D/1D models incorporating both surface and sewer drainage systems. To assess flood risk, the
consequences can be estimated using hydraulic model results, such as water velocities and water
depth results; the likelihood was estimated based on the return period of historical rainfall events. To
test the methodology two rainfall events with return periods of 350 and 2 years observed in
Alcântara (Lisbon, Portugal) were used and three consequence dimensions were considered:
affected public transportation services, affected properties and pedestrian safety. The most affected
areas in terms of flooding were easily identified; the presented methodology was shown to be easy
to implement and effective to assess flooding risk in urban areas, despite the common difficulties in
obtaining data.
