Making the Case for Stream Simulation Designs: Economic and Ecological Benefits

Stream simulation design is an ecologically-based approach to designing road-stream crossings that creates a dynamic channel through the crossing structure similar in dimensions and characteristics to the adjacent, natural channel, allowing for unimpeded passage of aquatic organisms, debris, and water over a range of flow conditions, including floods. A retrospective case study of the survival and failure of road-stream crossings was conducted in the upper White River watershed and the Green Mountain National Forest in Vermont following record flooding from Tropical Storm Irene in August 2011. Damage was largely avoided at two road-stream crossings where stream simulation design was implemented, and extensive at multiple road-stream crossings constructed using traditional undersized, hydraulic designs. Cost analyses suggest that relatively modest increases in initial investment to implement stream simulation designs yield substantial societal and economic benefits.  Case studies are presented to illustrate recent changes in policy and practice, and to help agencies and stakeholders improve road-stream crossings, including: increasing coordination to adopt stream simulation design methodology, increasing funding and flexibility for agencies and partners to upgrade failed crossings for flood resiliency, and expanding training workshops targeting federal, state, and local stakeholders.