Adapting to Climate Change: Assessing the World Bank Group ...

Appendix ERoadsRoads are vulnerable to climate risks, and these risks are likely to increase due toclimate change. The main threats come through an increase in extreme rainfall andstorm events (which can cause flooding or landslides that damage or destroy roadsections) and from sea level rise (which will worsen damage from storm surge andcoastal flooding and may even eventually lead to inundation). 68 The largest impactswill be for roads in upland areas with steep topography, and for coastal roads inareas vulnerable to storm surge. For example, a World Bank analysis of the impacton climate change on roads in Ethiopia found that in the absence of adaptivemeasures, costs to road users from climate events could double by 2050 (COWI2010).Normative ConsiderationsManaging climate risks has long been part of best practice in road design. Damagefrom storms and flooding can be reduced through physical measures (includingboth structural drainage and protective measures, and bio-engineering options suchas use of vegetation for slope stabilization or run-off management) and throughimproved capacity (for road maintenance, land management, warning systems, andemergency response systems). It is difficult to make broad claims about the costeffectivenessof particular measures, because the impacts vary widely depending ontopography, climate, and other factors.Design features of roads have different lifetimes, hence different sensitivities toclimate variability versus climate change. Short-lifetime features should be designedwith current climate variability in mind. For instance, pavement standards orembankment height can be readjusted to current temperature, flood, and trafficconditions when a road segment is rehabilitated—typically every 20 years. Withinthis timeframe, climate change is too slow to affect pavement standards. 69 Longerlivedand more inflexible are drains, culverts, and bridges, so these require moreconsideration of climate change impacts during their operating lifetime. Longestlivedof all is the decision on routing, which can affect spatial development patterns(and exposure to climate risk) for centuries. (See Box 4-2. in the main text.)Adaptive management and targeted improvements may be more efficient thanimmediate or blanket techniques. An analysis of road options in Mozambique underclimate change (Arndt and others 2011) compares and contrasts a strategy ofadaptive management—gradually rehabilitating existing roads and building new117