Taming global flood disasters Lessons learned fro

Authors: Chris Zevenbergen Sebastiaan van Herk Jeroen Rijke Pavel Kabat Pieter Bloemen Richard Ashley Andrew Speers Berry Gersonius William Veerbeek

Publish Date: 2012/10/13

Volume: 65, Issue: 3, Pages: 1217-1225

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Abstract

There is a growing international recognition that flood risk management in optima forma should be a programmed and flexible process of continuously improving management practices by active learning about the outcome of earlier and ongoing interventions and drivers of change In the Netherlands such a longterm adaptive flood risk management strategy is now being implemented This socalled second Delta Programme aims to identify and exploit opportunities and capitalize on shortterm benefits and opportunistic synergies that arise from change and will require adaptive policymaking It also requires the financial and institutional means to operate in a longlasting way which at the very least means engaging stakeholders gathering and disseminating results and adaptation of future plans Transferring the Dutch approach to other countries is a major challenge that calls for fundamental changes in institutional arrangements at various levels and thus requires customized programmes for strategic institutional change Recent examples of transfer will provide important lessons of how institutional change can successfully occur and will contribute insights for other countries that attempting to reform their flood risk management strategies Continuous monitoring and evaluation and sharing international experiences will become crucial for the effective delivery and wider uptake of these new strategies around the globeThe frequency and consequences of extreme flood events have increased rapidly worldwide in recent decades eg Bouwer et al 2007 Kron 2009 The global flood cost has reached a total of USD470bn since 1980 HSBC 2011 With the occurrence of more than 100 disastrous floods worldwide 2011 was a recordbreaking year ibid with extreme floods in Australia January Brazil January China June Colombia January–June the United States June and August Pakistan September Cambodia September Vietnam October Thailand November and in the Philippines December Climate change is likely to exacerbate this trend in the near future eg IPCC 2007 Adikrai et al 2010 The key drivers for these increases are the world’s population growth and the increase in socioeconomic activities in floodprone areas and their growing interdependency on flood protection and drainage infrastructure of which a significant part is of unknown or poor condition Ashley and Cashman 2006 National Committee on Levee safety 2009 Verwey 2011It is timely to take stock of the lessons learned from the past and ongoing flood disasters In the Netherlands through investments of more than €1bn per year and fullscale in situ experiments new approaches are now being developed to help to ‘live with water’ rather than fight it These are providing the insights tools and commitment needed to develop and implement longterm robust flood risk management strategies that facilitate adaptive responses to unforeseen change through partnership working and active learning Kabat et al 2005 Stive et al 2011 van Herk et al 2011a b These strategies are flexible de Haan et al 2011 in order to exploit the many opportunities for mainstreaming and integration of flood risk management into national and regional policies land management practices urban regeneration and in identifying and delivering multiple benefits at a local levelHistorically floods were viewed as ‘acts of God’ as disruptions to normality Mauch 2009 Responses were based on the assumption that floods were external events that affected an unknowing and unprepared society In the recent past however major flood disasters have acted as catalysts for changing flood risk management policies ibid The majority of these policies have focused on protection eg Saeijs 1991 and during the 20th century the scope shifted from indigenous localscale to largescale protection such as flood embankments and channelization This shift to largescale engineering responses was mainly driven by economic development and technological innovation Nevertheless the resulting policies remained ad hoc and post hoc responses to disasters and as a consequence the measures evolved over time in a piecemeal and fragmented way This approach has worked reasonably well in the recent past when the external drivers were assumed to change only slowly in comparison with the expected lifetime of the infrastructure systems but this is no longer tenable due to a faster pace of change Goodess et al 2009 Hulme et al 2009 Gersonius et al 2010More recent experience has revealed important limitations to these engineeringbased practices These include the following incorrect design assumptions that is circumstances for which the systems were designed proved to be more severe than originally predicted inadequate funding systems never meeting their design criteria and poor maintenance the performance of the systems declining over time eg Gordon and Little 2009Towards the end of the 20th and early in the 21st century the context of flood management shifted to a riskbased management strategy in which flood risk is defined as the probability of failure multiplied by the magnitude impacts of adverse affect eg Vrijling et al 1998 Even with this change in concept a lack of appreciation of the nonstationarity of drivers and the complex system dynamics particularly under the influence of climate and socioeconomic changes meant that conventional flood risk assessments were frequently misunderstood as providing a false sense of “full safety” Milly et al 2008 Another limitation has been the lack of socioeconomic concepts and methodologies to account for secondary economic consequences such as longterm disruptions to economic chains ripple effects Serre et al 2011 Lack of understanding of the complex linkages between subsystems and services and the cascading effects of one subsystem upon another such as for example between water supply energy production and transportation is a significant constraint to establishing the full benefit and costs of any proposed flood risk management strategy ibidThere are many opportunities for reducing flood vulnerabilities in the face of global change and the importance of integrating social and economic as well as technical approaches has now been widely accepted eg Scheur et al 2011 Whilst ageing infrastructure and building stock in the developed world pose a risk due to increasing vulnerability this also provides an opportunity to introduce new technologies in the redevelopment process and to adapt infrastructure and buildings to enhance flood resilience eg van Ree et al 2011 Urban restoration regeneration and modernization can be a key driver of economic development both as a result of the initial investments required and the benefits that will accrue over time eg formerly floodprone areas may become available for productive use Conversely many new economies and developing countries do not have to deal with the legacy of inadequate or declining assets and investments and this provides an opportunity for them to use the lessons from the developed world to avoid the past mistakes and utilize new innovative technologies ideas and best practice especially with regard to interconnecting systems eg Li 2011The Netherlands is one of the most flood vulnerable countries on the planet with more than 60  of the land area located in floodprone areas hosting 9 million residents and roughly 65  of the country’s gross national product Kabat et al 2005 Flood safety is not taken for granted but a huge and continuous effort is required to protect the country against flooding Currently the Netherlands is protected from storm surges and river floods by ongoing reinforcement of the flood protection system comprising coastal dunes dikes and storm surge barriers the Delta Works These were developed and implemented by the first Delta Committee in the 2nd half of the 20th century in response to the major flood disaster of 1953 in the first Delta Programme The safety standard for the reinforcement of the flood defence systems at the time was determined by a combination of the investments required to raise and/or strengthen the flood protection system and the expected reduction in potential direct damage cost the socalled riskbased benefitcost design approach van Dantzig 1956

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