Fort Gibson Lake — The Roles of a Dam and its Reservoir
Fort Gibson was established in 1824 on the Neosho River 40 miles southeast of Tulsa, Oklahoma by Colonel Matthew Arbuckle of the US 7th Infantry. Named after Colonel George Gibson, it was, at the time of its establishment, the Western most establishment of the US Government. A host of famous American generals spent time at the fort, which was used as a primary element to settling the west after the end of the American Civil War. Fort Gibson Lake was created in 1953 when construction of a dam was completed five miles north of Fort Gibson. The construction began in 1942, but was interrupted by the resource needs of the Second World War.
A site with so much history as well as the recreational opportunities created by fishing and public use areas nested along Fort Gibson Lake, attracts people from all over the country. Fort Gibson Lake is a popular destination for hundreds of people looking to catch largemouth bass, walleye, catfish, and assorted pan fish. The US Army Corps of Engineers Tulsa District is responsible for ensuring that public use areas (PUAs) in the vicinity of Fort Gibson Lake are up to par with Corps standards.
To help meet that goal, the Tulsa District contracted with Continental Mapping to map approximately 238 acres of land around Fort Gibson Lake which contained six PUAs. The work was to support Tulsa District for the future development of a Geographic Information System (GIS) adequate for parcel mapping, land use, and floodplain and wetland delineation within the PUAs along the lake. Each of the locations in the scope of work are Class A camp sites that see frequent usage throughout the summer months, while one of the locations (the dam site) has year round popularity among anglers of all skill levels. The Corps was especially concerned about location of shoreline and high water marks at each PUA site. Tulsa District contracted Continental Mapping to provide 1”=50’ planimetric detail, a DTM mapping to support 1’ contours and 6” resolution color orthophotos to help them reach their goals. The project was flown at 1800 feet AMT (Above Mean Terrain).
Continental Mapping established the necessary ground control for the project prior to the acquisition of the aerial photography. Photographic targets were used to establish horizontal and vertical control points for aerial triangulation, control of digital orthophotography, and base map production. It took the four person crew several days to complete all necessary survey work. The total period of performance for all aspects in this project was roughly one year.
Dam the rain
An interesting sub story to this dam, and every other dam in the Tulsa District for that matter, is the front line role it played in the historic rainfall that pelted Oklahoma in the spring and early summer of 2015 (note the rain in the beginning of our video). Lives were lost and hundreds of cars abandoned, but it actually could have been much worse. With this particular rain season seeing far above average rainfall, the totals could have been beyond comprehension. As it turned out, the 2,107 flood control dams in Oklahoma saved an additional $91 million in damage during May alone. In typical rainfall years, US Army Corps of Engineers (USACE) estimates the annual average flood savings in the neighborhood of $88 million for the entire year. May was the wettest month in recorded Oklahoma history. The Southwestern Division of USACE estimates the total flood protection savings in the south central and southwestern United States topped $13 billion. This is where the mapping and modeling elements are critical. By understanding the lay of the land and doing hydrographic analysis, agencies can not only prevent bad situations from escalating into catastrophic ones, but they can also tell you how much money the infrastructure saved. When it comes to lives saved and over $90 million in damages prevented, the return on investment for dam infrastructure really hits home.
Dams across the country are aging, with the average age in the US being greater than 50 years. The Association of State Dam Safety Officials (ASDSO) has stated that the engineering life of the average dam is 50 years. Across the country aging pipes are backing up or rusting away and reservoirs are being increasingly bogged down with silt that takes up space intended to hold flood waters. Earthquakes in previously unexpected locations have pushed inspection groups into action. Many dams previously considered safe are now in peril should a large seismic event occur near them. Luckily, groups like USACE and ASDSO are hard at work identifying risks and coming up with solutions to extend the lives of dams. The price tag may be steep at times, but the human cost of deferring dam maintenance is even higher.
Surveying and mapping, geospatial data, and enterprise GIS systems play critical roles in the inventory, monitoring, and management of our aging dam infrastructure. These tools serve all people involved in dam management with important information to plan for and mitigate potential risk associated with dams. Whether it is to evaluate the risk of failure of an existing dam, plan for the construction of a new dam, or to remove an existing dam, the use of surveying and mapping technologies is critical.
