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Cost-Effective Levee Design for Cases Along the Meuse River Including Uncertain- Ties in Hydraulic Loads

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Cost-effective levee design for cases along the Meuse river including uncertain- ties in hydraulic loads B. Broers Delft University of Technology . Cost-effective levee design for cases along the Meuse river including uncertainties in hydraulic loads by Ing. B. Broers in partial fulfilment of the requirements for the degree of Master of Science in Civil Engineering at the Delft University of Technology, Faculty of Civil Engineering and Geosciences to be defended publicly on January 15, 2015 Student number: 4184408 Supervisor: Prof. dr. ir. M. Kok, TU Delft - Hydraulic Engineering section Thesis committee: Dr. ir. T. Schweckendiek, TU Delft - Hydraulic Engineering section Ir. drs. J. G. Verlaan, TU Delft - Construction Management and Engineering section Ir. S.A. van Lammeren, Royal HaskoningDHV Ir. drs. E. R. Kuipers, Waterschap Peel en Maasvallei An electronic version of this thesis is available at http://repository.tudelft.nl/. Preface This MSc Thesis reflects the final part of the Master of Science degree in Hydraulic Engineering at the Civil Engineering and Geosciences Faculty of the Delft University of Technology. The research is per- formed under guidance of the Delft University of Technology in cooperation with Royal HaskoningDHV and Waterschap Peel & Maasvallei. I like to thank many people for their support and cooperation during my graduation thesis. In the first place I thank my direct supervisors: Timo Schweckendiek, Enno Kuipers and Bas van Lammeren for their helpful feedback, enthusiasm and guidance during the thesis. Many thanks to Prof. Matthijs Kok for his support and advice. My thanks to Jules Verlaan too, who helped me especially in the field of LCCA. Furthermore I would like to thank my colleges at Royal HaskoningDHV, for all their advices and feedback regarding the contents as well as the process of the graduation thesis. It was great to experience the company in where I was able to talk to hydraulic-, management-, LCCA-, and engineering- specialists. The MSc thesis topic originates from the Waterschap Peel & Maasvallei. Designing levees, operat- ing with a limited budged and dealing with all kinds of stakeholders and preferences is not an easy task. In my view, looking for opportunities and considering innovative ideas characterize the water board. One of the largest struggles during my thesis was to find an appropriate scope which includes both; the large variety in aspects the water board (and engineering agencies) faces as well as the detailed level of some aspects to form comprehensive results. Many colleges of the Water board gave me insight into their levee management difficulties, took effort to help me whenever I need and are very open for discussions. Therefore my thanks to these colleges as well. At last I would like to thank my friends, family and especially my fellow students for their encouragement, supported and help with the English language. At last I like to give some thoughts to the lately published report giving answers to data which are assumed in this report. On the 16th of September 2014 the Delta-committee presented the Delta Programme 2015. This program gives insight into the new safety philosophy. The new annual flood probability of Arcen has to be less than 1/300. The program reported an annual flood probability of 1/1.000 for the city-centre boulevard of Venlo. within this research a safety level of 1/1.250 is used for both case studies. Some results, like the most economical attractive robustness of the levee height, are strongly related to these changes. The calculated robustness is overestimated, but this does not change the basic methodology. Furthermore the discount rate will be (re)investigated according to the report. The belief exist that the 5,5% total real discount rate can be to high due to economical and political reasons (DP2015). B. Broers Delft, December 2014 iii Summary After the flood of 1993 and 1995 in the Netherlands, flood risks in Limburg became an important dis- cussion. Each flood defence system along the river Meuse needs to be provided with a safety level with an annual failure probability of 1/250. In the nearby future a new safety philosophy will be in- troduced entailing new safety norms and calculations techniques. The water board needs to construct levees including the knowledge of this new safety philosophy. Additionally the water board faces more problems like limited space or an intense infrastructure around the current levees. Uncertainties in hydraulic boundary conditions influence the levee design, too. An over- and underesti- mation of these conditions may lead to a cost-inefficient levee design. Moreover, innovative alternatives may be good alternatives. Including the uncertainties in the levee design alternative analysis can lead to a better decision process in where these innovations become more attractive. The objective of this MSc-thesis is to investigate which balance between levee investments and ro- bustness is most cost-effective during the levee design alternative analysis, specified for cases along the river Meuse in Limburg. Robustness within this balance is related to the uncertainties in future hydraulic boundary conditions. The main research question of the MSc-thesis therefore is: What are cost-effective levee designs including uncertainties in hydraulic boundary conditions? This research uses two case studies; Arcen and Venlo. The case study of Arcen is used to define, design and screen levee design alternatives. Furthermore an optimization procedure is developed with this case study. In Arcen some of the important problems are that the present levee passes through peoples back yards, it has a very high present failure probability and there is not much available space. The second case study will be used to confirm or reject the preliminary conclusion drawn in the Arcen case study. In Venlo, along the river Meuse a boulevard is present. This boulevard is partly protected by a demountable stop-log system which currently does not fulfil the present safety assessment. Fu- ture developments, preferences of other stakeholders and large service costs leading to a re-analysis of the levee design. Levee design alternatives are formed by combining a levee alignment with a green or structural design type. Secondly design criteria are formulated to create sketch designs per levee alternative. Next, these alternatives are screened with a multi-criteria analysis based on criteria like costs, constructibility and hydraulic impact. Alternatives which turn out to be most attractive of the MCA are referred to as realistic alternatives. These will be investigated further with help of LCCA. Life Cycle Cost Analysis or LCCA is a widely acknowledged technique to support the alternative analysis. One of the methods is the so called Net Present Value (NPV) calculations which include investments as well as benefits. This methods suits perfectly to investigate the robustness and the effect of hydraulic boundary condition uncertainties to the alternative analysis. The investments in LCCA includes among others: Project-, maintenance-, service- and end-of-life costs within the analysis period of a project. The benefits of a levee design can be estimated by calculating the flood risk reduction between the present and new situation. The NPV of a levee design alternative can be found by subtracting the present values of the investments from the benefits. A discount rate and economical growth rate is used to perform these calculations. The theoretical framework of LCCA as stated above is adapted to the optimization procedure. The aim of this procedure is to find the optimum levee height (ℎ) by seeking the robustness (Δℎ) argu- ment wherein the NPV-function attains its maximum value. v vi Summary Here the robustness is the levee height above the required height which is necessary to fulfil the present safety standards (annual exceedance probability of 1/250). Overtopping and overflow is within this model the only failure mechanism. Figure 1: Schematic overview of the optimization procedure. Figure 1 illustrate the optimization procedure in where the robustness (Δℎ) is varied. The hydraulic boundary condition uncertainties are included probabilistically (design water levels related with a 100 year analysis period t=T). If the robustness is large enough (ℎ ≥ ℎ) no major maintenance is neces- sary. Otherwise the levee height has to be increased (Δℎ) at 푡 = 푇. The uncertainties in hydraulic boundary conditions are calculated with a Monte-Carlo simulation. The maximum physically possible discharge of 4.600 푚/푠 of the river Meuse is included into the optimization procedure. Within this research three different hydraulic boundary condition uncertainty aspects are analysed quantitatively, and assumed to be independent: • The uncertainty in future river widening projects; • the uncertainty in statistics; • the uncertainty in forecasted climate changes. The uncertainties of all hydraulic aspects are assessed with respect to the new safety levels. For both cases, an annual failure probability of 1/1.250 is used. Berkhof et al. (2013) selected areas which can be used as possible future river widening projects. two scenarios are analysed for the river Meuse. A triangular distribution is chosen to represent the future river widening projects. A normal distribution is assumed for the uncertainties in statistics as it resembles an error in the use of various distributions as well as the differences in discharge measure methods and the extrapolation error. Rules of thumb are used to assume a uniform distribution for future water level increases in order to include uncertainties in forecasted climate change. A 95% confidential interval is chosen between the most positive and negative extreme scenario’s drawn up by the KNMI (van den Hurk et al. 2006). MSc thesis Bart Broers Summary vii A sensitivity analysis with help of a FORM-simulation shows that all three hydraulic boundary con- dition aspects contribute significant. The outcome of the optimization procedure of case study Arcen shows a large robustness of 0,6 meter for the case study Arcen for all levee design alternative.
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