Approach
Engineers often apply standards for sizing and placement of infrastructure with reference to historical hydrological datasets, yet climate change is shifting watershed hydrology outside of historical norms, in some cases increasing external stresses and loads on infrastructure and decreasing design life. Any upgrades or reinforcement of infrastructure to accommodate these increasing environmental stresses could be informed by projected changes in hydrology, extremely high temperatures on surfaces, and increased winter soil moisture timing and extent. Such reinforcement approaches may be especially relevant when seeking to defend infrastructure in order to maintain access and safety
Tactics
- Replace undersized culverts with bottomless culverts using bankfull width to guide design, using USFS stream simulation design that allows for sediment and debris to safely pass during higher flows or floods.
- Install emergency or auxiliary flow routes and overflow paths to prevent road blowouts and associated erosion, scour and sedimentation to protect adjacent or downstream wetlands.
- Where water control structures are used, install auxiliary or emergency overflow routes to mitigate high water conditions, or at least conduct a cost-benefit analysis to consider whether risks from more extreme hydrologic events warrant an investment...
- If water level or flow control structures are necessary, consider control structures that provide operational flexibility and adaptability.
- On low-volume roads or trails, convert culverts to, or supplement culverts with a low-water crossing structure (ford or low-water bridge) designed to be overtopped or impacted by woody debris or ice during floods.
Strategy
Strategy Text
This strategy addresses adapting infrastructure designs and maintenance to support wetland ecosystems under changing environmental conditions, including infrastructure found within or near wetland watersheds such as bridges, culverts, stream crossings, roads, trails, parking lots, utilities, coastal structures, docks, and piers. Roads, stream crossings, recreational trails, facilities, and other infrastructure are known to affect local landforms and hydrology, particularly where impervious surfaces concentrate water into flow pathways, generating high-velocity runoff and erosion. For this reason, critical evaluation of past design concepts and criteria with additional consideration for a changing climate and altered hydrology may be necessary to minimize risks and safety concerns over the designed lifespan of the unit. A changing climate challenges traditional perceptions of “low maintenance” infrastructure that can be built and left unattended, and heightens the necessity of increased infrastructure monitoring, inspection and routine maintenance. Contemporary philosophies for wetland management, enhancement and restoration have shifted toward the minimization of traditional infrastructure in the watershed, and incorporating natural or low impact development to dissipate excess water can both reduce negative downstream impacts and reduce the need for hard infrastructure. However, changing environmental conditions also merit renewed consideration of infrastructure designs that recognize changing conditions to support wetland function and watershed management.