A GIS for Flood Risk Management in Flanders

Abstract

In the past decades, Flanders, a region of north Belgium that extends from the coastline inland (in northwest Europe), has suffered several serious riverine floods that caused substantial property damage. As Flanders is one of the most densely populated regions in the world, a solid water management policy is needed in order to mitigate the effects of this type of calamity. In the past, Flemish water managers chose to drain off river water as quickly as possible by heightening the dikes along the rivers. However, this method leads to a higher flood probability further downstream. Moreover, water defence infrastructure can always suffer from technical failures (e.g., breaching) creating even more damage than would have occurred if no defences were in place. In a search for a better solution to this recurring problem, the Flemish administration proposed a new approach in the 1990s. This approach focuses on minimizing the consequences of flooding instead of attempting to prevent floods. To implement this approach, large amounts of data were gathered for the Flemish Region. Using a Geographic Information System (GIS), a risk-based methodology was created to quantitatively assess flood risk based on hydrologic models, land use information and socio-economic data. Recently, this methodology was implemented in a specifically designed GIS-based flood risk assessment tool called LATIS. By estimating the potential damage and number of casualties during a flood event, LATIS offers the possibility to perform risk analysis quickly and effectively. This chapter presents a concise overview of LATIS' methodology and its implementation for flood risk management in Flanders.

Analyzing the sensitivity of a flood risk assessment model towards its input data

“…In a first step, a benchmark flood risk model was determined. This model was created using all available data and was based on the Flemish LATIS methodology (Deckers et al, 2010) and on a risk assessment performed by ODPEM (2013a). In the benchmark risk assessment, geographic information was combined with the replacement values of the elements at risk and with the damage factors.…”

“…The line dataset was converted into polygons, based on the different widths. Using an average maximum road damage, calculated by Collier et al (2013) for developing countries, and combining this with damage factors from the Flemish LATIS flood risk assessment tool (Deckers et al, 2010), the real damage was then calculated for all roads.…”

“…These approaches, however, have shown limited success in several countries (Gall et al, 2011;Deckers et al, 2010), leading to new approaches that focus on flood risk management rather than flood control (Institute for Water Resources, 2009). One of these approaches is a quantitative flood risk assessment, indicating the high-risk areas by estimating the possible damage caused by a flood hazard.…”

“…Furthermore, an increase of the input data accuracy doe not automatically imply a decrease of the output's uncertainty (Apel et al, 2009). Nonetheless, the existing models are being optimized and are used as decision tool in urban planning projects as is the case in Flanders, Belgium (Deckers et al, 2010).…”

Flood Damage Assessment in a Gis – Case Study for Annotto Bay, Jamaica

“…Technocratic interventions to prevent damage, such as dams, levees, and flood forecasting, have shown limited success in the past [3,7]. In order to truly minimize the socio-economic cost induced by inundations, an adequate flood risk assessment is necessary to compute the damage of future floods as accurately as possible.…”