Uncertainty in levee heights and its effect on the spatial pattern of flood hazard in a floodplain

Abstract

Levees are not usually built to a uniform height due to the varying priority of protecting urban and agricultural lands and they are often maintained in segments. Ad hoc alteration of the heights of these segments may aggravate flood conditions. Alterations lead to complex feedback loops in velocity and depth of water that are difficult to predict. A large number of possible configurations of the levee segments renders a deterministic modelling approach ineffective. The current analysis, based on a two-dimensional hydrodynamic model involving 1000 Monte Carlo realizations of randomly varying levee heights in segments, presents a methodology of dealing with the effect of uncertainty in levee heights on the inundation pattern in a probabilistic framework. Spatially distributed model outcomes include the likelihood of inundation, range and standard deviation of flood depths and maximum speed of water. The results indicate the necessity of adopting a probabilistic approach for robust flood hazard assessment when dealing with levee segments with uncertain heights. EDITOR M.C. Acreman; ASSOCIATE EDITOR H. Kreibich.