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Abstract: Session A  10:30 am (Back to Session A)
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Beyond NAACC: A Multi-Objective Road-Stream Crossing Assessment Protocol

 Tim Koch
Cornell Cooperative Extension of Ulster County
Shokan, NY

Road-stream crossings (RSXs) are key components of resilient streams and communities. Comprehensive assessments of RSXs are warranted due to their ubiquity in the landscape, impacts on stream morphology, channel stability, base flood elevations, and propensity for longitudinally fragmenting stream networks. RSX assessments in the Northeast and Mid-Atlantic regions are often completed using the North Atlantic Aquatic Connectivity Collaborative (NAACC) protocol. NAACC is an ecological assessment method focused on aquatic organism passage (AOP). Minimal attention is paid to the structural condition (SC), flow capacity (FC), or geomorphic compatibility (GC) of the structure and the stream. Therefore, we developed an integrated, multi-objective stream crossing assessment protocol (MOSCAP) in order to prioritize RSXs based on a suite of relevant data. Three existing field protocols focused on AOP, GC, and SC, respectively, and a desktop hydraulic analysis that estimated the return interval FC of individual structures were integrated into a unified assessment and prioritization protocol. Scoring involved a customizable weighting scheme that generated a numeric Priority Level score. The integrated score served as a better prioritization tool than NAACC alone. Four RSXs in the Catskills Mountains town of Olive were deemed flood hazards by an outside consultant. All four RSXs were ranked by NAACC as Minor Barriers to AOP. The score range was 8.0%, making objective prioritization equivocal. The MOSCAP Priority Level scores ranged from 35.9-69.7% and helped to clarify the highest priority crossing. The customizable weighting strategy allows users to influence scoring based on local concerns and promotes buy-in from municipal highway managers more concerned with SC than AOP. Survey time per crossing using the MOSCAP averaged 26 minutes, a small increase if any from a NAACC-only assessment. Additionally, MOSCAP results showed that lower order RSXs (1-3) consistently scored lower in GC, FC, AOP, Priority Level, and were significantly more severe hydraulic constrictions than higher order crossings. Building resilient streams and communities, especially around RSXs, requires assessing more than AOP. Further MOSCAP implementation will not only improve RSX assessments and prioritization but may continue to uncover trends such as the under-appreciated role that low-order RSXs may be having on network scale stream stability.