IPCC Report.pdf - Adam Curry

Chapter 5Managing the Risks from Climate Extremes at the Local Levelemploy engineering works to provide protection from flooding such asdikes, embankments, seawalls, river channel modification, flood gates,and reservoirs. However, structural measures also include those thatstrengthen buildings (during construction and retrofitting), thatenhance water collection in drought-prone areas (e.g., roof catchments,water tanks, wells), and that reduce the effects of heat waves (e.g.,insulation and cooling systems). Although many of these structuralinterventions can achieve success in reducing disaster impacts, they canalso fail due to lack of maintenance, age, or due to extreme events thatexceed the engineering design level (Galloway, 2007; Doyle et al., 2008;Galloway et al., 2009). In the event that the frequency and magnitudeof extreme events increase as a result of climate change, new designlevels may be necessary. Technical considerations should also includelocal social, cultural, and environmental considerations (WMO, 2003;Opperman et al., 2009).Implementing structural measures from planning through implementationthat involve participatory approaches with local residents who areproactively involved often leads to increased local ownership and moresustainable outcomes. Such an example is a program of building,managing, and maintaining cyclone shelters in Bangladesh (Zimmermannand Stössel, 2011). One of the key reasons why sub-national structuralprojects are often ineffective is that they are approved on the basisof technical information alone, rather than based on both technicalinformation and local knowledge (ActionAid, 2005; Prabhakar et al.,2009; see also Section 5.4.4). In addition, national legislation hasimportant influences on the choice of disaster risk reduction strategiesat the local level as local and national institutional arrangements thatoften favor structural responses over other non-structural approaches(Burby, 2006; Galloway, 2009). Technological responses alone may alsohave unintended geomorphologic and social consequences, includingincreasing flood hazard in downstream locations, increasing costs oflong-term flood protection works, or increasing coastal erosion in areasdeprived of sediments by coastal protection works (Adger et al., 2005;Hudson et al., 2008; Box 5-3).The method of protecting an entire area by building a dike has been inuse for thousands of years and is still being applied by communities inflood-prone countries. Embankments, dikes, levees, and floodwalls areall designed to protect areas from flooding by confining the water to ariver channel, thus protecting the areas immediately behind them.Building dikes is one of the most economical means of flood control(Asian Disaster Preparedness Centre, 2005). Dikes built by communitiesnormally involve low technology and traditional knowledge (such asearth embankments). Sand bagging is also a very common form offlood-proofing. Generally, structures that are built of earth are highlysusceptible to erosion, leading to channel siltation and reduced waterconveyance on the wet side and slope instability and failure on the dryside. Slopes can be stabilized by various methods, including turfing byplanting vegetation such as Catkin grass and Vetiver grass inBangladesh and Thailand, respectively. However there is a continuingdebate in the region as to whether the grass strips prevent erosion,whether erosion is in fact the main problem instead of soil fertility, andwhether farmers still need slope stabilization (Forsyth and Walker,2008).Decisionmaking for large-scale structural measures is often based oncost-benefit analyses and technical approaches. In many cases,particularly in developed countries, structural measures are subsidizedby national governments and local governments and communities arerequired to cover only partial costs. In New Zealand, this led to apreponderance of structural measures despite planning legislation thatenabled non-structural measures. As a result, the potential for majordisasters was increased and development intensified in areas withstructural measures only to be seriously devastated by events thatexceeded the engineering design level (Ericksen, 1986). Reduction ofcentralized subsidies in the mid-1980s and changes in legislation sawgreater responsibility for the costs of disaster risk management fallingon the communities affected and a move toward more integrateddisaster risk reduction processes within New Zealand (Ericksen et al.,2000). Similar trends have been observed in relation to coastal protection,where structural measures are often favored over non-structuraloptions (Titus et al., 2009; Titus, 2011).Building codes closely align with engineering and architectural structuralapproaches to disaster risk reduction (Petal et al., 2008; Kang et al.,2009). This is accompanied by the elevation of buildings and groundfloor standards in the case of flooding (Aerts et al., 2009; Kang et al.,2009). Though building code regulations exist, non-adoption, especiallyin developing countries, is problematic (Spence, 2004). Damages to thestructure occur not only because of noncompliance with the codes, butalso through a lack of inspections, the ownership status of the structure,and the political context and mechanisms of local governance (May andBurby, 1998). Insurance arrangements can provide incentives to localgovernments and households to implement building codes (Botzen etal., 2009).Short-term risk reduction strategies can actually produce greatervulnerability to future events as shown in diverse contexts such asENSO-related impacts in parts of Latin America, induced developmentbelow dams or levees in the United States, and flooding in the UnitedKingdom (Bowden et al., 1981; Pulwarty et al., 2004; Berube and Katz,2005; Penning-Rowsell et al., 2006). While locally based protectionworks often enable areas to be productively used and will continue tobe needed for areas that are already densely settled, they are commonlymisperceived as providing complete protection, and actually increasedevelopment – and thus vulnerability – in hazard-prone areas, resultingin the so-called ‘levee effect’ (Tobin, 1995; Montz and Tobin, 2008). Amore general statement of this proposition is found in the safe developmentparadox in which increased safety measures such as dams or leveesinduce increased development, which in turn leads to increased exposureand ultimately losses (Burby, 2006). The conflicting policy goals of rapidrecovery, safety, betterment, and equity and their relative strengths andweaknesses largely reflect experience with large disasters in otherplaces and times. The actual decisions and rebuilding undertaken todate clearly demonstrate the rush by government at all levels and the305