In response to multiple dam failures due to overtopping during hurricanes, the NC NCDEQ, Division of Energy, Mineral and Land Resources (DEMLR), began a multiyear plan in 2019 to assess the overtopping potential of the State’s 3,000+ jurisdictional dams.
The study was funded by the Disaster Recovery Act of 2016 and is part of an ongoing effort by Dam Safety to correlate dam susceptibility to overtopping failure with real-time rainfall data as an emergency response tool. WithersRavenel has been a consultant to the NCDEMLR from the program’s beginning, providing hydrologic and hydraulic analysis and dam surveys as the program continues to evolve.
WithersRavenel completed the surveying and reporting in accordance with Dam Safety’s specifications to ensure uniformity so results could be uploaded to a database for future use. WithersRavenel provided a standardization to the North Carolina State Plane system in locations and elevations that had previously been based on assumed coordinates in many cases. The results determined the overtopping potential of dams for use in emergency management response to hurricanes and other extreme flooding events. The data could then be used in singular or multiple watershed simulations with varied rainfall and time durations.
WithersRavenel completed detailed dam surveys in support of the DEMLR Dam Studies. The purpose of the survey and evaluations was for a new template entry for automation developed with teaming partner RTI. The template entry forms were developed in partnership to improve NCDEQ’s historic files of dam information. WithersRavenel field crews also created detailed notes in plan and profile of the impoundments along with updated imagery.
Conventional and GNSS Survey control was utilized on the site to create data for the template entries. Field crews completed a standardized set of photographs, data collection, and measurements on each of the dams. This updated imagery provided Dam Safety the most recent dam conditions. The survey data provided upstream, downstream, crest(s) of dam, primary and post outlets information. Past breaches and possible future breach situations were identified and documented. The work of WithersRavenel provided valuable support to NCDEQ’s regional dam engineers and Raleigh office.
The project and teaming provided invaluable benefits for NCDEQ. Dam ownership and contact information was updated or confirmed. Historical data on the dams was updated, corrected, or supplemented with better information. A uniform database with coordinate values on all the critical dam parts was created and could be used easily in the future. Once the study is complete and modeling performed, our state will be better prepared for safety though our surveys.