10 | Green Roads for Water
• In water catchments roads can manage water by controlling the speed of runoff, compartmentalizing and mitigating flood runoff (rather than concentrating runoff into fewer tributaries), and influencing the sedimentation process in the catchment. The choice of where to place a road within a catchment and which additional water-management measures to include has a major impact on how the catchment is managed.
THE THREE LEVELS OF PROMOTING RESILIENCE: PROTECTIVE, ADAPTIVE, AND PROACTIVE Considerable debate is ongoing on the effect of climate change on road infrastructure. The conversation centers on how to manage more intensive runoff, more frequent flood peaks, and rising temperatures. Ebinger and Vandijcke (2015) state that the loss caused by disrupted transport infrastructure can be enormous, and sheltering roads from climate impacts is extremely important to economies. The concern for resilient roads often translates into a protective resilience or basic resilience approach under which road infrastructure is safeguarded from inclement weather events at any cost (Cervigni et al. 2016; FarragThibault 2014; Douglas et al. 2017; NDF 2014; Transportation Research Board and National Research Council 2008). Under a protective approach to resilience, road infrastructure specifications are adjusted to account for specific climate risks such as temperature rise, higher flood peaks, loss of permafrost, more extreme freeze and thaw cycles, or extreme cold. This approach treats stresses as exogenous and follows traditional methods for engineering roads to withstand environmental stresses. The first downside of the protective resilience approach is that it often improves the resilience of the road at the expense of the resilience of the natural or human-made environment. For example, protective resilience often calls for protecting the road from higher flood peaks with better cross drainage. Although protecting the road is essential to keeping the economy running, larger cross drainage immediately passes the impact of extreme weather events onto the surrounding area, causing more severe floods, more inundation, and heavier e rosion. Because roads often divert water from natural drainage paths and concentrate it, the volume of water passing through the enlarged drain may be far greater than natural flows. Although the road is protected, the landscape around it often suffers even more from the effects of climate change. These impacts may also harm the built environment, such as farmers’ fields or downstream settlements. The second downside is that this protective approach does not use the road’s potential to improve water management and the climate resilience of the surrounding area. Not only can improved water management protect the landscape, it may also support nearby communities’ livelihoods, access to potable water and sanitation, and water security. This guideline advocates alternatives to the protective approach that could be called resilience plus. The “plus” involves integrating water management into road development and design. This approach adapts or designs roads to fit within the landscape in various ways that allow them to support improved management of water and the local environment, including managing water for the benefit of nearby communities. In most cases, the roads-for-water approach (the resilience plus approach) will reduce road damage from water just as well
