Utilizing Drone Imagery to Provide an Emergency Repair from a 35,000 cfs Strom Event
Phillip Todd
Freese & Nichols, Inc
Raleigh, NC
Ian Jewell
Liam Hales
Freese & Nichols, Inc
Winston-Salem, NC
Authors: Bryan M. Dick, PhD, PE, PH, Ian Jewell, JD and Emily Brown, PhD Candidate, PE,
Slow erosion over time became magnified by high water flows when the City of Winston-Salem experienced a severe rainfall event in Spring 2020. Over a span of 4 days, Winston-Salem received almost 7 inches of rain. Downstream gage stations registered flows upward of 35,000 cubic feet per second (cfs) with base flows typically around 3,000 cfs. Resulting damage along the project’s 300 feet of Salem Creek amounted to substantial erosion and debris jams, the collapse of 15-feet-high banks, and the threat of exposure of a major force main and fiber optic line, leaving both utilities in imminent danger of damage and major disruptions to critical services in the City.
An initial assessment was followed with additional site visits and use of drone technology, combined with modeling, to develop a project design. This effective technique assisted with identifying site conditions, determining potential design options and selecting the most effective repair technique to serve the City and provide long-term bank stabilization.
Drones allowed for initial assessment of erosion damage and provided a footprint of sandbars that had developed downstream over time. The team also used the drone for monitoring stream movements throughout the project. The team utilized drone imagery, in combination with modeling and design techniques, to develop the channel alignment, map sediment movement and effectively address underlying issues in the channel causing streambank erosion. The design provides a favorable stream restoration solution that addresses the redirection of water flow in order to rebuild the bank and protect crucial Infrastructure while also lessening future sediment accumulation, facilitating better conveyance of water and sediment along Salem Creek and lessening the chances of future erosion at this location.
Project construction was completed in the spring of 2021. In winter 2022, the American Council of Engineering Companies - North Carolina recognized the project with an Honors Award.
This presentation will share the effectiveness of using drone technology along with typical stream restoration design techniques to stabilize threatened infrastructure and note project success.
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