NCDEQ Dam Site Survey and Evaluations – WithersRavenel

NCDEQ Dam Site Survey and Evaluations

About This Project

WithersRavenel provided site survey and evaluations of the 265 selected high hazard dams in the Cape Fear River Basin. This was WithersRavenel’s third river basin project in partnership with NCDEQ.  The previous work was completed in the Lumber and Neuse basins, which served as proving grounds for the state’s largest basin.

The study was funded by the Disaster Recovery Act of 2016 and is part of an ongoing effort by NCDEQ, Division of Energy, Mineral and Land Resources (DEMLR), Dam Safety to study flooding in the watersheds for use in emergency management. Recent rainfall events in 2017 and 2019 caused multiple dam breaches across the state, and updating information was necessary to ensure public safety.

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.

Surveying & Geomatics