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Adaptation to extreme rainfall in the Netherlands: a strategic balance between structural and non-structural measures

Congress: 2008
Author(s): Martine Ruijgh-van der Ploeg, Job van Dansik

AbstractAdaptation to extreme rainfall in the Netherlands: a strategic balance between structural and non-structural measures Martine Ruijgh-van der Ploeg, Delft University of Technology, Delft, Netherlands Job van Dansik, Delfland Regional Water Authority, Delft, Netherlands Corresponding author: Martine Ruijgh-van der Ploeg Correspondence Address: P.O. Box 5015, 2600 GA Delft, The Netherlands Telephone: + 31 15 215 7723 E-mail Address: M.P.M.Ruijgh-vanderPloeg@tudelft.nl Preferred mode of presentation: Oral presentation Congress sub-theme: Theme 4 Development of water resources and infrastructure Introduction - In 1998 and 1999 extreme rainfall caused the stormwater management system to fail in the water authority district of Delfland (40,000 ha; 1.2 million people). Large urban, industrial and agricultural areas were flooded, the safety of several levees was jeopardized. The elected representatives urged the water authority to immediately take action to prevent such events in the future. A strategy was to be developed; many uncertainties about the future were to be dealt with. In 2001 the implementation of (non)structural measures was started. All measures are being taken in response to the ongoing change of rain patterns as caused by climate change. Effectiveness of structural measures was evaluated in 2006; completion is planned for 2015. The lessons drawn from 10 year practice by the water authority of Delfland can be adopted in developing best practices for climate adaptation strategies in densely populated and built -up regions. Objective of this paper is to present a (conceptual) model of the adaptation strategy. Elements of the model are the guiding principles and objectives used in design of (non)structural measures, performance criteria, design space, testing procedures, and the uncertainties that influence model outcome. With this model we evaluate the choice of structural and non-structural measures in the climate adaptation strategy. Method used is an action research approach. The analytical framework applied stems from design and adaptive water management theories that we are familiar with as reflective practitioners. We made the observations while actively participating in the processes of design and implementation of the adaptation strategy. The authors serve as, respectively, member of the executive board and policy maker/engineer of the water authority of Delfland. Results The adaptation strategy consists of both structural measures (pumping stations, widening of canals, large stormwater storage facilities) and non-structural measures (e.g. crisis management organization, tax policy, spatial plans, cooperative water governance). The major uncertainties stem from climate, spatial planning, costs of structural measures, and willingness of municipalities and other parties to cooperate. The major objective for the adaptation strategy is to create a robust and adaptable water system by 2015 at acceptable costs. This translates in evaluation criteria as robustness of operational management, rate of implementation, costs and benefits, and cost sharing. Guiding principles for strategy design are: anticipate rather than react; combine different (non)structural measures; avoid passing on of responsibilities; involve spatial planning authorities in decision-making for water management. Applying these principles, the stormwater management system was redesigned. Prioritization of flood-prone areas directs the step-wise implementation of structural measures. Non-structural measures are implemented in the entire district; the order of implementation is determined by the degree of (political) cooperation required. In 2008 all 14 municipalities will have spatial plans that enable the necessary structural measures. The success of the implementation so far can be explained by the linkage of structural and non-structural measures. All non-structural measures contribute to the robustness and adaptability of the renewed water system, or to the funding of structural measures and speedy implementation.
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