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A1) Life-cycle performance

Start: 09/2017
End: 09/2021
Status: Active

Contact details

Wouter Jan Klerk

Delft University of Technology

Expected outcome

Optimisation techniques and decision trees to align the inspection, maintenance and reinforcement of flood defences, such that future life-cycle performance can be enhanced.

Example of the activities to ensure life-cycle performance: 1) construction, 2) monitoring, 3) inspection, and 4) reinforcement (Photos accordingly by Pascal Ogink, Wouter Jan Klerk, Mark van der Krogt and the Flood Protection Program).

Motivation and practical challenge

The asset management of flood defences in the Netherlands (see photo) has been built upon centuries of experience. We have taken great leaps in quantifying the performance of these structures based on failure probabilities and understanding typical failure mechanisms. Yet, there is a danger that some elements are missing over the life-cycle management. As a researcher, but also advisor, for flood risk asset management, I realised that some connections are not well incorporated. These limited connections are, for example, between reinforcement, inspection and maintenance. To efficiently manage our flood defences in the future, we need to integrally look at all the activities and related choices that are part of the management cycle. This integrated approach will help us to explain and check for the failure probabilities that we compute, which are so important to comply with the targets of the new flood protection standards. Furthermore, this approach will optimise future inspection and reinforcement decisions.

Research challenge

The challenge is, therefore, to develop methods for addressing the missing connections between dike reinforcement, maintenance, monitoring, and inspection at different spatial and temporal scales. By doing so, how does, for example the reinforcement of a diaphragm wall at one spot (bottom-right photo above) help the safety targets for a larger dike section in the coming decades? How does inspection help in maintaining sufficient reliability?

Components of the research relating decisions at a dike section to a whole segment. (sources: figure 1 adapted from van Beek (2015) including dike segment scheme prepared by Richard Marijnissen.

Innovative components

This research uses smart optimisation techniques to relate measures at different spatial scales. For instance, such a technique was applied to a dike reinforcement project to derive optimal planning of different measures (figure 1 and 2). By using this technique, the system reliability requirement, incorporating all failure mechanisms, was met optimally when looking at costs and performance.

I use decision trees and Bayesian decision analysis to incorporate monitoring and inspection results to reduce uncertainty in the dike strength parameters (figure 3). Moreover, a pivotal part of reducing uncertainty in performance are periodic visual inspections (figure 4). However, the accuracy (the inspector sees, i.e., how much?) is unclear and to determine it a field experiment was conducted. The insights can be used in optimising inspection frequencies and methods.

In the last stage of this research, I will develop an approach to consider uncertainty reduction at a system level. For instance, by deriving optimal inspection strategies for revetments a large dike system, such that inspections can be done risk-based.

Relevant for whom and where?

Within the Netherlands, this research is of relevance to the regional water authorities, the Dutch Flood Protection program and the Ministry of Water and Infrastructure. In an international context, anyone with a keen interest in risk/performance-based asset management of flood defences can use it in defining projects and optimising inspections and maintenance.


The research includes key locations for the reinforcement of a dike section and the field experiment to assess the quality of inspections.

Progress and practical application

First findings (click on related outputs below) show that the smart optimisation of reinforcement projects can reduce dyke reinforcement costs by about 40%. In studies on the effectiveness of proof loading and dike monitoring cost savings were in the range of ~25% have due to the achieved uncertainty reduction. However, not only cost savings were achieved but also risks are avoided. For example, when including the potential occurrence of cracks in an asphalt revetment, the estimated failure probabilities differ orders of magnitude from the values estimated from the safety assessment. First example applications on the studied locations illustrate the importance of an integral life-cycle management approach for managing flood defences efficiently. However, findings also show that it is hard to determine deterioration rates based on existing inspection data. For the future, an improvement in data collection from the inspections is therefore required.

Status for day-to-day practice

Most of the methods developed explicitly aimed at practical application. Optimisation of dike reinforcement projects can, for instance, be done with hardly any additional information. For inspection optimisation, some data on degradation is to be available.

Next steps

Practical implementation of the risk-based asset management methods developed in this research has made clear that data on flood defence deterioration (e.g., from inspections) is scarce. Additionally it is found that a fundamental understanding of the performance of (slightly) damaged flood defences is lacking. An example is the strength of placed block revetments with loose blocks. Strengthening knowledge on these topics will increase the value of the developed approaches.

Last modified: 03/11/2020

Main researcher

Wouter Jan Klerk

Delft University of Technology

Contributors

Wim Kanning

Delft University of Technology

prof.dr.ir. Matthijs Kok

Delft University of Technology

prof. Dr. Ir. Rogier Wolfert

Delft University of Technology

Contributing partners

Proof loading and monitoring to optimize flood defence asset management

We calculate the expected value of extra information obtained from proof loading and monitoring. The additional information improves failure probability estimates for slope stability.

Mark van der Krogt

Delft University of Technology

Wouter Jan Klerk

Delft University of Technology

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Project outputs

A framework for assessing information quality in asset management of flood defences

Methodology for scoring quality and use of available information for decision-making and assessing of the value of additional information.

28/10/2018 by Wouter Jan Klerk et al.

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Bevat: Conference proceedings

Risk based inspection of flood defence dams: An application to grass revetments

Method to derive risk-based inspection intervals using visual inspection data and a combined degradation and failure model.

28/10/2018 by Wouter Jan Klerk et al.

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Bevat: Conference proceedings

Value of Information of monitoring in the management of flood defences

Analysis of the Value of Information for different monitoring strategies combined with dike reinforcements to identify the conditions under which monitoring pore pressure is most beneficial for long-term asset management.

30/08/2019 by Wouter Jan Klerk et al.

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Bevat: Publication open access journal

Time-dependent reliability in flood protection decision making in the Netherlands

Exploration of the failure probability definition and the influence of including temporal correlation on failure probability estimates.

17/06/2018 by Wouter Jan Klerk et al.

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Bevat: Conference proceedings

Influence of monitoring on investment planning of flood defence systems

Exploring the value of monitoring for the reinforcement of a dike segment.

11/12/2019 by Wouter Jan Klerk et al.

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Bevat: Conference proceedings

Blogs

Bringing All-risk to practice: Martin’s recommendations

08/10/2020 by Wim Kanning

This blog is based on an informal interview between Martin Schepers (manager flood safety projects) and Wim Kanning (All-Risk researcher) on the development of...

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Events

17/05/2021

All-Risk webinar 17 mei

Dubbele dijken: dubbel beschermd en dubbel verantwoordelijk?

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10/12/2020

NCR Lecture: A system perspective on flood defence reinforcement projects

Wouter Jan Klerk talked on the NCR December's lecture about the Dutch flood probability standards, and how he works to optimise the way we reach our risk-based target levels. In the dike reinforcement Streefkerk-Ameide-Fort Everdingen a method was developed and applied to optimize flood defence investments at a system level.

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