The role of bathymetry, wave obliquity and coastal curvature in dune erosion prediction

Low lying coastal areas have always been attractive for people to live, but are also prone to flooding. In The Netherlands, half of the population lives in the coastal area below mean sea level where two-thirds of the economic value is located. Coastal dunes protect the hinterland from flooding as a primary sea defence along the major part of the Dutch coastline. The envisaged protection level of the densely populated and economically valuable areas is one of the world’s highest, with a normative failure probability of O(1× 10−5 year−1). The extreme storm events of this order of magnitude are not observed in (known) recent history. Hence, design, evaluation and maintenance of flood defence systems that can resist these extreme normative conditions rely on models and data extrapolations. The safety assessment method for the Dutch dune coast includes an empirical dune erosion model (DUROS+) and boundary conditions that represent the normative loading (semi-probabilistic). Every six years, a safety assessment is performed for a series of cross-shore dune profiles along the coast. The prediction skill of the DUROS+ model is limited due to its empirical nature and the omission of the alongshore dimension. The model only takes the upper part of the cross-shore profile explicitly into account and does not account for effects of wave obliquity and coastal curvature. Several dune erosion models have been developed over the last two decades that provide the means to model the dune erosion process in a more comprehensive way. In addition, probabilistic methods have improved and computational power has increased, potentially allowinga probabilistic safety assessment of complex dune areas to be performed. The aim of this thesis is the reduction of uncertainty in dune erosion prediction, in particular at complex dune coasts, in order to improve dune safety