Benbrook Lake
Encyclopedia
Benbrook Lake is a reservoir
on the Clear Fork of the Trinity River
in Tarrant County, Texas
, USA. The lake
is located approximately 10 miles (16 km) southwest of the center of Fort Worth
, where the Clear Fork and the West Fork of the Trinity River join. The lake is impounded by the Benbrook Dam. The lake and dam are owned and operated by the U.S. Army Corps of Engineers
, Fort Worth District.
Benbrook Dam and Lake were built by the Galveston District of the Corps of Engineers. During the decade of active civil works construction following World War II, the U.S. Congress provided for the construction of Benbrook Lake, Grapevine Lake
, Lavon Lake and Ray Roberts Lake as well as modifications to the existing Garza Dam for the construction of Lewisville Lake
. The River & Harbors Act of 1945 authorized these projects for the purposes of both flood control and navigation. These lakes and others, along with an extensive floodway system of levees, are operated in a coordinated manner to minimize flooding along the Trinity River floodplain corridor in the Dallas/Fort Worth Metroplex
.
A second major influence for development was the desire of commercial interests for a shipping channel along the length of the Trinity River. This project, in its most grandiose design, was envisioned as a 9 feet (2.7 m) by 150 feet (45.7 m) canal (2.74 × 45.72 m) running upstream from Trinity Bay on the Gulf Coast to Dallas
, and west all the way to Fort Worth. Downstream it would connect to the Houston Ship Channel
. Twenty-six separate lock
and dam
projects were to be constructed. Today a ship channel is maintained upriver as far as river mile
41 (km 66) near Liberty, Texas
. Although unlikely, a navigation channel linking Fort Worth to the Gulf of Mexico
could still be constructed.
Water originally intended for use in this navigation channel was only recently reallocated for municipal water use. The Tarrant Regional Water District in 1992 gained these water rights and now provides water supply to the cities of Benbrook
, Fort Worth, and Weatherford
. The Water District has also built pipelines that connect Benbrook Lake with the Fort Worth’s Rolling Hills water plant and both Cedar Creek
and Richland-Chambers
reservoirs southeast of Dallas.
Construction of Benbrook dam began in May 1947, and was practically completed when floodgates were closed and deliberate impoundment was begun in September 1952. The cost to build the lake was $14.5 million ($112 million in 2007 dollars). The rolled-earth embankment is 9,130 feet (2,783 m) in length, including the concrete spillway, and rises 130 feet (39.6 m) above the streambed to an elevation of 747 feet (227.7 m) above sea level. A pair of 6.5 feet (2 m) × 13 feet (4 m) sliding gates operated by electric cable hoists controls the floodwater releases through the 13 feet (4 m) . Two 30-inch-diameter pipes (0.76 m) are provided for low-flow releases to maintain downstream river flows. The concrete spillway for uncontrolled releases is 500 feet (152 m) long, with a 100 feet (30.5 m) in its center.
At the normal, or conservation pool, level of 694 feet (211.5 m) above sea level, the lake covers 3,770 acres (15 km²). This would increase to 7,630 acres (31 km²) if the lake ever reaches the nominal maximum flood pool elevation of 724, which is also the overall spillway elevation at the top of the center notch.
One design option considered during the planning stages for the lake included an alternate damsite near the current I-20
bridge over the Trinity River, 3.7 feet (1.1 m) downstream from the final, chosen location.
There was much more to construction than simply building the dam. Several railroads, roads and bridges, utility lines and cemeteries were relocated. The largest of these jobs was the rerouting of six miles (10 km) of the Gulf, Colorado and Santa Fe Railway
. Gravesites from seven separate cemeteries were relocated to the Benbrook municipal cemetery at Winscott and Mercedes. No significant cultural, archeological or paleontological features existed in the project area, according to the July 1948 preconstruction survey.
Design engineers for Lake Benbrook estimated that the lake would rise as high as the 710 feet (216.4 m) spillway elevation only about every forty years, and elevations of 715 feet (217.9 m) or greater would be reached only once every one hundred years. These estimates show how unusual and remarkable were the flood events of 717 feet (218.5 m) in May 1989, 718 feet (218.8 m) in May 1990, and 713 feet (217.3 m) in December 1991.
Water releases from Benbrook Lake are made primarily through a 13 feet (4 m) gated conduit at the southeast end of the dam. When waters rise too quickly to be released by this method, then the lake may flow over the uncontrolled spillway at the northwest end of the dam. This spillway is a 500 feet (152.4 m) concrete weir with a 50 feet (15.2 m), 14 feet (4.3 m) notch in its center. As of 2005, there have only been five occasions on which the lake has been high enough for water to come over the spillway and through this notch. The lake has never been high enough to go over the entire width of the spillway, which is to be expected as the spillway was designed that this should happen only during a 100-year flood event.
Releases through the spillway continued for almost a month, until June 21. The peak elevation was on June 5 as the waters were flowing through the 50 feet (15.2 m) in a stream three feet deep, before falling back to the normal 694 elevation on the July 4.
Benbrook Lake then did not reach the 710 feet (216.4 m) spillway elevation again for over thirty-two years.
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
on the Clear Fork of the Trinity River
Trinity River (Texas)
The Trinity River is a long river that flows entirely within the U.S. state of Texas. It rises in extreme north Texas, a few miles south of the Red River. The headwaters are separated by the high bluffs on the south side of the Red River....
in Tarrant County, Texas
Tarrant County, Texas
Tarrant County is a county located in the U.S. state of Texas. As of the 2010 U.S. Census, it had a population of 1,809,034. Its county seat is Fort Worth. Tarrant County is the sixteenth most populous county in the United States and the third most populous in Texas. The county is named in honor...
, USA. The lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
is located approximately 10 miles (16 km) southwest of the center of Fort Worth
Fort Worth, Texas
Fort Worth is the 16th-largest city in the United States of America and the fifth-largest city in the state of Texas. Located in North Central Texas, just southeast of the Texas Panhandle, the city is a cultural gateway into the American West and covers nearly in Tarrant, Parker, Denton, and...
, where the Clear Fork and the West Fork of the Trinity River join. The lake is impounded by the Benbrook Dam. The lake and dam are owned and operated by the U.S. Army Corps of Engineers
United States Army Corps of Engineers
The United States Army Corps of Engineers is a federal agency and a major Army command made up of some 38,000 civilian and military personnel, making it the world's largest public engineering, design and construction management agency...
, Fort Worth District.
History
Significant flooding on the Trinity River during May 1908, April 1922 and September 1936, was a primary cause for the development of Corps of Engineers flood control projects in North Texas.Benbrook Dam and Lake were built by the Galveston District of the Corps of Engineers. During the decade of active civil works construction following World War II, the U.S. Congress provided for the construction of Benbrook Lake, Grapevine Lake
Grapevine Lake
Grapevine Lake is a freshwater lake located in the north Texas area, approximately northwest of Dallas, Texas. It was impounded in 1952 by the US Army Corps of Engineers when they dammed Denton Creek. The lake's primary purposes are flood control and to act as a water reservoir, with a secondary...
, Lavon Lake and Ray Roberts Lake as well as modifications to the existing Garza Dam for the construction of Lewisville Lake
Lewisville Lake
Lewisville Lake is a reservoir located in North Texas on the Elm Fork of the Trinity River in Denton County near Lewisville. The lake is primarily used recreationally for boating and watercraft, however, it was built for flood control purposes and to serve as a water source for Dallas and its...
. The River & Harbors Act of 1945 authorized these projects for the purposes of both flood control and navigation. These lakes and others, along with an extensive floodway system of levees, are operated in a coordinated manner to minimize flooding along the Trinity River floodplain corridor in the Dallas/Fort Worth Metroplex
Dallas/Fort Worth Metroplex
The Dallas–Fort Worth–Arlington Metropolitan Statistical Area, a title designated by the U.S. Census as of 2003, encompasses 12 counties within the U.S. state of Texas. The area is divided into two metropolitan divisions: Dallas–Plano–Irving and Fort Worth–Arlington. Residents of the area...
.
A second major influence for development was the desire of commercial interests for a shipping channel along the length of the Trinity River. This project, in its most grandiose design, was envisioned as a 9 feet (2.7 m) by 150 feet (45.7 m) canal (2.74 × 45.72 m) running upstream from Trinity Bay on the Gulf Coast to Dallas
Dallas, Texas
Dallas is the third-largest city in Texas and the ninth-largest in the United States. The Dallas-Fort Worth Metroplex is the largest metropolitan area in the South and fourth-largest metropolitan area in the United States...
, and west all the way to Fort Worth. Downstream it would connect to the Houston Ship Channel
Houston Ship Channel
The Houston Ship Channel, located in Houston, Texas, is part of the Port of Houston—one of the United States's busiest seaports. The channel is the conduit for ocean-going vessels between the Houston-area shipyards and the Gulf of Mexico.-Overview:...
. Twenty-six separate lock
Lock (water transport)
A lock is a device for raising and lowering boats between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is...
and dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
projects were to be constructed. Today a ship channel is maintained upriver as far as river mile
River mile
In the United States, a River mile is a measure of distance in miles along a river from its mouth. River mile numbers begin at zero and increase further upstream. The corresponding metric unit using kilometers is the River kilometer...
41 (km 66) near Liberty, Texas
Liberty, Texas
Liberty is a city in and the county seat of Liberty County, Texas, United States and a part of the Houston-Sugar Land-Baytown metropolitan area. The population was 8,033 at the 2000 census....
. Although unlikely, a navigation channel linking Fort Worth to the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
could still be constructed.
Water originally intended for use in this navigation channel was only recently reallocated for municipal water use. The Tarrant Regional Water District in 1992 gained these water rights and now provides water supply to the cities of Benbrook
Benbrook, Texas
Benbrook is a city located in the southwestern corner of Tarrant County, Texas, in Texas's 12th congressional district, and a suburb of Fort Worth...
, Fort Worth, and Weatherford
Weatherford, Texas
Weatherford is a city in Parker County, Texas, United States, and a western suburb of Fort Worth. The population was 19,000 at the 2000 census. It is the county seat of Parker County and is part of the Dallas-Fort Worth Metroplex.-Geography:...
. The Water District has also built pipelines that connect Benbrook Lake with the Fort Worth’s Rolling Hills water plant and both Cedar Creek
Cedar Creek Reservoir (Texas)
Cedar Creek Reservoir is a reservoir located in Henderson and Kaufman Counties, Texas , 60 miles southeast of Dallas. It is built on Cedar Creek, which flows into the Trinity River...
and Richland-Chambers
Richland-Chambers Reservoir
Richland-Chambers Reservoir is the third largest inland reservoir by surface area and the 8th largest reservoir by water volume in Texas formed by the impoundment of Richland Creek and Chambers Creek east-southeast of the town of Corsicana and south of Kerens, in Navarro County and Freestone...
reservoirs southeast of Dallas.
Construction of Benbrook dam began in May 1947, and was practically completed when floodgates were closed and deliberate impoundment was begun in September 1952. The cost to build the lake was $14.5 million ($112 million in 2007 dollars). The rolled-earth embankment is 9,130 feet (2,783 m) in length, including the concrete spillway, and rises 130 feet (39.6 m) above the streambed to an elevation of 747 feet (227.7 m) above sea level. A pair of 6.5 feet (2 m) × 13 feet (4 m) sliding gates operated by electric cable hoists controls the floodwater releases through the 13 feet (4 m) . Two 30-inch-diameter pipes (0.76 m) are provided for low-flow releases to maintain downstream river flows. The concrete spillway for uncontrolled releases is 500 feet (152 m) long, with a 100 feet (30.5 m) in its center.
At the normal, or conservation pool, level of 694 feet (211.5 m) above sea level, the lake covers 3,770 acres (15 km²). This would increase to 7,630 acres (31 km²) if the lake ever reaches the nominal maximum flood pool elevation of 724, which is also the overall spillway elevation at the top of the center notch.
One design option considered during the planning stages for the lake included an alternate damsite near the current I-20
Interstate 20
Interstate 20 is a major east–west Interstate Highway in the Southern United States. I‑20 runs 1,535 miles from near Kent, Texas, at Interstate 10 to Florence, South Carolina, at Interstate 95...
bridge over the Trinity River, 3.7 feet (1.1 m) downstream from the final, chosen location.
There was much more to construction than simply building the dam. Several railroads, roads and bridges, utility lines and cemeteries were relocated. The largest of these jobs was the rerouting of six miles (10 km) of the Gulf, Colorado and Santa Fe Railway
Gulf, Colorado and Santa Fe Railway
The Gulf, Colorado and Santa Fe Railway was a subsidiary of the Atchison, Topeka and Santa Fe Railway in eastern Texas and to Purcell, Oklahoma.- Nineteenth Century :...
. Gravesites from seven separate cemeteries were relocated to the Benbrook municipal cemetery at Winscott and Mercedes. No significant cultural, archeological or paleontological features existed in the project area, according to the July 1948 preconstruction survey.
Flooding and operational history
Flooding in May 1949 claimed eleven lives in Fort Worth and cost $11 million to local businesses, as construction for the dam was beginning. During a spring 1957 flood, the new lake and the downtown floodway prevented $9.3 million in damages, almost recouping the original construction costs of the lake. During this flood, the lake filled to its 694 feet (211.5 m) conservation level for the first time on May 12, 1957; the spillway elevation of 710 was reached on May 26 that year, with a record pool of 713.35 on June 6, 1957. This elevation was a record that lasted thirty-two years, but was then surpassed twice in an eleven-month period from June 1989 to May 1990. The current record pool level is 717.5 feet (218.7 m) above sea level and occurred on May 3, 1990. Flood damages prevented by Benbrook Lake from 1989 through 1991 have pushed the total savings for the life of the lake to over one billion dollars. When holding floodwaters, the lake pool rises above the normal elevation of 694 feet (211.5 m). This often requires closing of park roads and other facilities for extended periods.Design engineers for Lake Benbrook estimated that the lake would rise as high as the 710 feet (216.4 m) spillway elevation only about every forty years, and elevations of 715 feet (217.9 m) or greater would be reached only once every one hundred years. These estimates show how unusual and remarkable were the flood events of 717 feet (218.5 m) in May 1989, 718 feet (218.8 m) in May 1990, and 713 feet (217.3 m) in December 1991.
Flooding History at Benbrook Lake
The idea of a flood control reservoir like Benbrook Lake, is that floodwaters from heavy rains are retained above the dam. This reduces river flows downstream of the dam, and so prevents property damage and losses, but lake levels above the dam rise, and lands surrounding the lake are inundated. In other words, flooding is not eliminated, but its location is predetermined—it will be along the undeveloped lakeshore area upstream of the dam, rather than along the industrialized or populated downstream river valley.Water releases from Benbrook Lake are made primarily through a 13 feet (4 m) gated conduit at the southeast end of the dam. When waters rise too quickly to be released by this method, then the lake may flow over the uncontrolled spillway at the northwest end of the dam. This spillway is a 500 feet (152.4 m) concrete weir with a 50 feet (15.2 m), 14 feet (4.3 m) notch in its center. As of 2005, there have only been five occasions on which the lake has been high enough for water to come over the spillway and through this notch. The lake has never been high enough to go over the entire width of the spillway, which is to be expected as the spillway was designed that this should happen only during a 100-year flood event.
1957 Flooding
Spring rains in 1957 first filled the lake to its normal conservation pool elevation of 694 NGVD (National Geodetic Vertical Datum or feet above sea level) for the first time. Lake waters rose some 30 feet (9.1 m) from April 1 through May 12 of that year, and by May 26 had risen another sixteen feet, overtopping the 710 feet (216.4 m) spillway elevation for the first time.Releases through the spillway continued for almost a month, until June 21. The peak elevation was on June 5 as the waters were flowing through the 50 feet (15.2 m) in a stream three feet deep, before falling back to the normal 694 elevation on the July 4.
Benbrook Lake then did not reach the 710 feet (216.4 m) spillway elevation again for over thirty-two years.