The safety of large flood defences will thus be impacted less by multifunctional use than conventional assessments would suggest, but flood protection benefits of multifunctional use will also be limited. Furthermore, the influence of multifunctional use on safety is proportional to the size and protection level of the flood defence itself. This is most notable when the dominant failure mechanism is directly affected by the multifunctional use. As the analysis shows, the current conservative approach can lead to a significant overestimation of the probability of failure compared to a scenario-approach, up to several orders of magnitude. Assessments made of a dike containing of common multifunctional elements (house and tree). To answer the first question a scenario-based approach already suggested in grey-literature was compared to the existing conservative approach. Therefore, the aim of this research is: to investigate how combining different activities on or near flood defences affects the safety provided by flood defences assessed with a risk-based approach.įor this research, four research questions are addressed through case studies: 1) How can a dike assessment framework be adapted to probabilistically evaluate multifunctional use of a flood defence? 2) How can additional defences constructed for multifunctional use of the flood protection zone be incorporated and evaluated within a probabilistic evaluation framework? 3) How can a probabilistic framework account for long-term climate adaption benefits of multifunctional use within a flood protection zone? To do so an integrated risk assessment framework is required. With the new probabilistic risk approach recently adopted in the Netherlands, it is possible to improve the methodology for assessing multifunctional flood protection. While in current practise multifunctional use generally imposes strict restrictions on the design of flood defences due to safety concerns, multifunctional-use may in some cases contribute to reducing flood risk instead. This shared-use of the flood defences often comes with conservative estimates for a robust design that guarantees the flood safety standards are met. Nevertheless, flood defences are often integrated with many other functions such as housing and nature.

The primary purpose of flood defences is protect people and their livelihoods from flooding.

Richard flood 2021