NCHRP Research Report 853: Guidance for Design Hydrology for Stream Restoration and Channel Stability provides written guidance and interactive tools to help hydraulic engineers assess the current conditions adjacent to a stream crossing and in the upstream watershed. Specifically, the guidance and tools provide support to determine design effort, performing the appropriate hydrological and geomorphic analysis using a set of analytical and analog tools, and designing the channel through the stream crossing for stability and sediment balance.
Several decision support/analysis tools were developed to improve and facilitate design hydrology analyses. The tools include: (1) a decision tree to be used with web-based hydrologic analysis tools (eRAMS) for generating design hydrology metrics under existing and future land use scenarios, (2) guidance on relating channel response potential to an appropriate level of design analysis, (3) guidance on selection of analog reaches and performing rapid geomorphic assessments of channel instability in the field, and (4) a spreadsheet-based Capacity Supply Ratio Tool (CSR Tool) for computing analytical channel designs that account for the full spectrum of sediment transporting events.
The Implementation Effort
NCHRP Project 20-44(15) aimed to give the target audience, including hydraulic and bridge engineers, designers, hydrologists, geomorphologists, and other practitioners, the necessary tools to integrate sediment transport into their designs. Some of the major tasks of the project included:
Three regional, two-day workshops conducted to provide participants with firsthand experience using the information from NCHRP Report 853, including the Capacity Supply Ratio (CSR) tool and flow duration curves (FDC).
Site visits to demonstrate field techniques close to each training facility.
Identification of regional points of contact (i.e., subject matter experts) to provide ongoing, supplemental technical support.
Documentation to agency-specific resources developed to support implementation along with specific examples of projects completed using the design analysis tools.
The workshops trained participants to assess stream response potential and compute analytical channel designs to balance water and sediment using the capacity supply ratio (CSR) spreadsheet tool as published in NCHRP Report 853. A combination of lecture and hands-on sessions provided practical experience in the context of relevant case studies. Participants learned about general sediment transport principles, rapid evaluation of channel instability, appropriate levels of analysis, flow duration curves for gauged and ungauged sites, sediment supply, and design reach capacity. Innovative adaptation of the class materials for the online workshop format included a virtual field trip to demonstrate the rapid geomorphic assessment techniques, plus drone footage of one of the central case studies.
The final report for NCHRP 20-44(15) can be accessed here.