Sensitivity of pump design to the method to assess the influence of persistent periods of extreme sea water levels

Discharging excess water from regulated water systems in low-lying coastal areas will likely become more difficult due to sea level rise. The functionality of existing discharge sluices will decrease as the discharge window shortens. Additionally, high sea water levels can cause a decrease in the pump capacity of pumping stations, as they would operate far from the optimal operating point.  This reduction in discharge capacity may lead to an increase in flood risk in  water systems, requiring new or expansions of existing pump-sluice stations.

An accurate representation of high sea water levels due to tides and storm surges is essential to correctly determine the required pump-sluice capacity and operational head  for new pump-sluice stations. To asses the effect of storm tides on a water system we are mainly interested in persistent periods of high water levels, their temporal evolution and their distribution. Storm tide models can provide the time series of high sea water levels and the associated statistics required for the pump-sluice design process. Most available models can be sorted in to three types of approaches: long measurement time series,  generation of stochastic events, physics-based or stochastic-based long synthetic time series.  

In this study different storm tide models were used to assess the functionality of our pump-sluice station design. A comparison shows that the application of different methods leads to very different results in our pump design. Given that all models are plausible, this introduces an important source of uncertainty, which has to be taken into account in the design phase to prevent over- and under-designing.