Fault tree analysis for urban flooding.
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.
ten Veldhuis
J A E
JA
Department of Water Management, Delft University of Technology, Delft 2600 GA, The Netherlands. j.a.e.tenVeldhuis@tudelft.nl
Clemens
F H L R
FH
van Gelder
P H A J M
PH
D002947:Cities; D003663:Decision Trees; D055868:Floods; D008962:Models, Theoretical; D009426:Netherlands; D018570:Risk Assessment; D014887:Weather