Spatial integration of dike reinforcements
Development of a method that compares the spatial influence of design alternatives
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Abstract
In the Netherlands, a new assessment method for the required safety level of primary flood defences is introduced in the Water Act. It is estimated that currently roughly 1900 kilometres of flood protection does not meet the safety requirements for the future (Jonkman, Jorissen, Schweckendieck & Van den Bos, 2017). Past flood defence projects show that integrating reinforcement measures is a difficult assignment.
It is specifically focused on dike reinforcement projects in this thesis. A deficiency in the design process is identified in the role that the influence on the existing situation has on the evaluation and selection of design alternatives that are input for the Environmental Impact Assessment. The difficulty for improving the importance of the existing situation in the surroundings, in the design process is that the subject experts on these themes are typically assessing the consequences of proposed interventions (Aalberts, 2018).
The research objective is set to develop a method that allows to include the influence on the existing situation within the evaluation and selection of design alternatives in dike reinforcement projects. This method aims for providing information to compare the spatial integration of reinforcement designs in early stages of reinforcement projects. Subject experts should assess the provided information, and determine whether a reinforcement design provides a satisfying influence on the project area. It is focused on dike reinforcement projects in rural area.
A research through design study is used to develop the method to compare design alternatives. The study included the identification of technical design measures to increase the strength of dikes in rural area, and the decomposition of rural areas in functional characteristics that can be valued. A conceptual evaluation model is developed to express the relation between functional characteristics and design alternatives for dike reinforcements. It is studied how a method can be provided to compare the outcome of the conceptual evaluation model for a large variety of design alternatives. The value of the developed method is assessed in a case study, which is the dike reinforcement project “Wolferen-Sprok”.
The resulting method is able to compare design alternatives on the influence on the existing situation by following seven steps. It is providing design measures for the identified safety problem of the dike in a certain project area. Simultaneously, the characteristics of the project area should be identified and visualized on maps. This provides the required information to apply the conceptual evaluation model that identifies effects of design alternatives on the existing situation. The retrieved data is visualized to compare design alternatives.
It is concluded that the developed method focusses mainly on natural, cultural, and social economic functions in rural project areas. This means that influence of design alternatives on costs, maintainability, and landscape values should be addressed separately, in the evaluation and selection of design alternatives. It is recommended to study how the influence on these topics can evaluated in a similar method.
The developed method can be applied to include the existing situation in the project area in the evaluation and selection of design alternatives in dike reinforcement projects in rural areas. It is expected that application of the method in design teams provides new input for further improvement of the method.