It is not uncommon for a flood defence to be combined with other societal uses as a multifunctional flood defence, from housing in urban areas to nature conservation in rural areas. The assessment of the safety of multifunctional flood defences is often done using conservative estimates. This study synthesizes new probabilistic approaches to evaluate the safety of multifunctional flood defences employed in the Netherlands and explores the results of these approaches. In this paper a case representing a typical Dutch river dike combining a flood safety function with a nature and housing function is assessed by its probability of failure for multiple reinforcement strategies considering multiple relevant failure mechanisms. Results show how the conservative estimates of multifunctional flood defences lead to a systematic underestimation of the reliability of these dikes. Furthermore, in a probabilistic assessment uncertainties introduced by multifunctional elements affect the level of safety of the dike proportional to the reliability of the dike itself. Hence, dikes with higher protection levels are more suitable to be combined with potentially harmful uses for safety, whereas dikes with low protection levels can benefit most from uses that contribute to safety.@en

The goal of the study is to map the changes of marsh extent and topography on both Sturgeon Bank and Westham Island between 1980 and now. The study will look for a correlation between the recession and the possible loss of sediment from the banks. If a sediment deficit is a (major) contributor of marsh recession within the Fraser Delta, the results of the study should reveal such a connection. Although there are plenty of studies suggesting changes have taken place in the marshes fronting the Fraser Delta, no study has utilized the extensive data record of satellites to study these changes for the entire Fraser Delta. Tools like the Aquamonitor can detect the changes in coastlines in the past 30 years from satellite imagery. More advanced tools are still in development like MI-SAFE, which detects inter-tidal elevations and vegetation on foreshores to estimate the potential risk reduction of flooding by coastal vegetation all across the world. Within the study the latest techniques from these tools are applied and adapted to the Fraser Delta. By using the full 30+ years of information on satellite imagery, the marsh and inter-tidal surface changes are examined from a new angle. @en