The joint impact of storm surge, fluvial flood and operation of man-made structures on the high water level frequency in the Lower Rhine Delta

v Summary Most deltas of the world and their highly urbanized environments, are vulnerable to flooding, and thus, the consequences in terms of human fatalities and economic losses are serious. Floods and the consequent damages have triggered significant developments of flood protection measures. Flood risk is expected to be much more serious in the future. On the one hand, climate change is exacerbating mean sea level rise and intensifying extreme river floods, consequently increasing high water level frequency. On the other hand, deltas are rapidly experiencing urbanization, which results in increasing vulnerability of deltas. High water levels in deltas are the result of interaction between natural flood sources (high astronomical tides, storm surges, river flooding, high intensive precipitation, or combination of more than one variable) and human interventions (flood control measures to reduce flood sources). In this thesis the joint impact of storm surges, fluvial floods as well as the operational water management system on the high water level frequency is estimated in the Lower Rhine Delta. A fully probabilistic approach is developed for resampling extreme hydrodynamic boundary conditions of the Lower Rhine Delta as well as the time revolution. The first application of a joint probability approach in the Lower Rhine Delta dated back to 1969 (Van der Made, 1969). It only considered the peak values of the sea level and the Rhine flow, assuming the other associated variables (such as the storm surge duration) to be predetermined as constant values. Nevertheless, at present these associated variables play an important role in determining the water level in the delta. For example, the Maeslant barrier and the Haringvliet Dam with sluices should be closed when a storm surge occurs. A storm surge duration can affect the closure duration of the Lower Rhine Delta and therefore can influence the water level in the inland delta. In the fully probabilistic approach these associated variables will be taken into account. In the fully probabilistic approach, joint probability distributions of extreme hydraulic load variables derived from the observed flood events are applied to re-sample a large number of scenarios of storm surges, Rhine floods as well as Meuse floods. These scenarios drive a deterministic model to result in water levels at the locations of interest. These water levels can be converted into high water level frequency at locations. This approach enables assessment of the high water level frequency in a changing environment with associated …