Comprehensive risk-perspective for flood defence system management
Frank den Heijer (TU Delft - Hydraulic Structures and Flood Risk)
Matthijs Kok – Promotor (TU Delft - Hydraulic Structures and Flood Risk)
Pieter van Gelder – Promotor (TU Delft - Safety and Security Science)
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Abstract
Asset management of flood defences systems includes strategic, tactic and operational decision levels. Since risk is a key parameter for asset management, risk management capabilities are important for the maturity and quality of flood defence asset management. The main objective is to develop and test methods for risk analysis in flood defence system management subject to deterioration and climate change. It focusses on three questions which elaboration can improve the risk-based management of flood defences, one at each of the three asset management decision levels.
The first is: How can the structural robustness of the flood defence contribute to flood risk reduction? An integrated risk analysis has been set up, valuing the risk reduction due to the structural robustness of a construction type, represented by its ductile behaviour during high loads. Therefore, the consecutive occurrence of initial dike failure mechanisms, failure path development, breach growth and consequences is modelled integral and time dependent.
The second is: How can planning of measures contribute to effective system risk reduction? Therefore, the interventions or measures are studied for a system of dikes in flood-prone areas, which are continuously required to mitigate changes such as ageing and climate change. A method is developed to compare different tactical plans to prioritize and plan measures in interdependent systems of dikes, to reduce risks most effectively and efficiently.
The third is: How can risk-based standards for flood defences reflect the benefits of structural robust designs? Therefore, it is studied how economic optimal probabilities of dike failure, can be updated to reflect the impact of structural robust dike designs. Furthermore, an analytical relation is developed for economic optimal design horizons. Finally, a dynamic and simple to use approach is developed to enable updating of the economic optimal reliability, based on a proposed design and planning. Therewith, it is practical possible to keep a dynamic focus on the optimal economic risk.
Risk analysis is an indispensable element in risk-informed decision making on each of the asset management decision levels used in asset management practices. The concept of a dynamic connected risk analyses is combined with the concept of decision levels, and the concept of the Deming circle as an organisational concept for continuous capability improvement. Coherent use, can bridge the practical disconnections between the decision levels.
Following the topics elaborating the questions, case studies are carried out showing the importance and impact. The main contribution of the work performed is that it provides a comprehensive perspective for the utilization of risk analysis as a tool supporting efficient flood defence system management.