Traditional methods to evaluate flood risk generally focus on heavy storm events as the principal cause of flooding. Conversely, fault tree analysis is a technique that aims at modelling all potential causes of flooding. It quantifies both overall flood probability and relative contributions of individual causes of flooding. This paper presents a fault model for urban flooding and an application to the case of Haarlem, a city of 147,000 inhabitants. Data from a complaint register, rainfall gauges and hydrodynamic model calculations are used to quantify probabilities of basic events in the fault tree. This results in a flood probability of 0.78/week for Haarlem. It is shown that gully pot blockages contribute to 79% of flood incidents, whereas storm events contribute only 5%. This implies that for this case more efficient gully pot cleaning is a more effective strategy to reduce flood probability than enlarging drainage system capacity. Whether this is also the most cost-effective strategy can only be decided after risk assessment has been complemented with a quantification of consequences of both types of events. To do this will be the next step in this study.
Research Article|April 01 2009
Fault tree analysis for urban flooding
J. A. E. ten Veldhuis
F. H. L. R. Clemens
Water Sci Technol (2009) 59 (8): 1621-1629.
J. A. E. ten Veldhuis, F. H. L. R. Clemens, P. H. A. J. M. van Gelder; Fault tree analysis for urban flooding. Water Sci Technol 1 April 2009; 59 (8): 1621–1629. doi: https://doi.org/10.2166/wst.2009.171
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