GIS-integrated pluvial flood risk assessment methodology for urban areas

Abstract

[EN] To different extents, most urban areas in Europe are exposed to pluvial flood hazards. The local communities, as well as city governments have to find measures either to cope with the consequences or look for solutions to prevent the possible damage of the floods. Moreover, in most cases cities cannot be transformed to be flood resilient with single isolated interventions, but need an adaptive approach for flood-conscious governance and management. For this, cities require up-to-date information on the flood risk, to make data-based decisions on how to avoid disastrous events, plan for flood resilient high-quality living environment, and where relevant, design and implement transformative interventions. The conventional definition of disaster risk combines the likelihood of potential hazard, exposure magnitude, and the level of vulnerability. However, when considering the multifaceted challenge of assessing the susceptibility and damage potential of urban pluvial flooding, this three-dimensional risk assessment methodology is not yet widely implemented. Additionally, a standardized risk management framework proposes an iterative risk assessment procedure, which could be well-suited for an adaptive governance approach. However, until now, the pluvial flood risk assessment has not been fitted to this framework. In the paper, we present a tiered pluvial flood risk assessment methodology, which can be applied to any urban area. The proposed solution couples the disaster risk function with the standardized iterative risk assessment procedure. This allows cities in various entry-level preparedness to improve their understanding of the city-wide pluvial flood susceptibility and identify the flood-prone urban watersheds in which more specific risk analyses are required. The methodology includes coupling a digital twin of an urban drainage system (UDS) and a geographical information system (GIS). By integrating the pluvial flood risk assessment procedure in the city GIS the cities can automatically determine the potential hazard and coping capacity of exposed areas, and analyse the concurrent vulnerabilities. The methodology has been tested in a small, but densely populated urban area in Estonia, Rakvere town.