3 research outputs found
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Session B1: Lessons Learned from Tropical Storm Irene 2.0: How Flood Resiliency Benefits of Stream Simulation Designs Are Changing Policy within the U.S.
Abstract
Stream simulation design is a geomorphic, engineering, and ecologically-based approach to designing road-stream crossings that creates a natural and 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 during various 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. Numerous other examples across the country of stream simulation designs surviving large flood events underscore these benefits. Four years after the historic Irene flood event, policy changes at state and federal levels across the U.S. suggest that the flood resiliency of culverts is gaining momentum as a policy driver amid growing public sensitivity to climate change risks and the importance of restoring ecological connectivity and protecting investments in transportation infrastructure
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Concurrent Sessions A: Co-Benefits of Barrier Removal: Fish Passage and Public Safety - Economic and Social Costs of Culvert Failures: Examining Tropical Storm Irene Impacts in Vermont
During Tropical Storm Irene in August 2011, valley towns in Vermont’s upper White River watershed experienced extensive flood damage, a portion of which was related to road failures caused by undersized or poorly designed road-stream crossings. The USDA Forest Service and its partners conducted a retrospective case study in the watershed to compare the resilience of road-stream crossings designed using traditional hydraulic methods with those designed using the stream simulation method. Undersized culverts may fail catastrophically during large storm events, threatening human safety and destroying public and private property. This presentation will review the costs that Vermont communities incurred from specific culvert failures and demonstrate how stream-simulation can be a cost-effective option, particularly as climate change increases the frequency and intensity of large storms. The survival of two recently constructed stream simulation design crossings and an additional ecologically-beneficial crossing on the Green Mountain National Forest (GMNF) highlighted the broader benefits of ecologically-beneficial designs, including reduced rates of crossing failure and storm damage to roads and property, reduced costs of road maintenance, and reduced likelihood of adverse impact to communities and businesses caused by flood damage
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Concurrent Sessions A: Co-Benefits of Barrier Removal: Fish Passage and Public Safety - Flood Resiliency, Aquatic Organism Passage, Critical Infrastructure, and Economics
A retrospective case study was conducted in the Upper White River subbasin in Vermont (Unthank et al 2012) that examined persistence of traditional hydraulic and stream simulation designs following the record flood flows from Tropical Storm Irene that occurred in August 2011. Analysis indicated that extensive damage to road infrastructure in this study area was largely avoided in areas where the stream simulation design approach was implemented, as did several other localized case studies from across New England. Benefit/cost analyses suggest that a relatively modest increase in initial investment to implement stream simulation designs to provide aquatic organism passage yield substantial societal benefits. When considering the overall comparative economic, social and natural resource costs to communities caused by crossing and/or road failure due to undersized road-stream crossings, adoption of stream simulation design is comparatively inexpensive when examined over a multi-year time frame. Hydraulic analysis results of stream simulation designed structures surviving Tropical Storm Irene will be presented along with a series of regulatory, policy and funding recommendations to help agencies, municipalities and communities make smart infrastructure and aquatic resource investments that reduce future road and stream crossing failures and associated impacts, and to help provide biological resilience and infrastructural persistence in the face of increased frequency and severity of flood events modeled under climate change