Clear Creek Watershed Authority

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Flood History

Frequent flooding in the watershed has caused considerable damage to roads, bridges, culverts, soils, livestock, crops, fences and other property.   A study by the USDA SCS (NRCS) for the 35 years prior to formation of the CCWA, indicated 116 storms that resulted in damage producing floods - more than 3 floods per year -  with estimated average annual direct monetary damage of $1,800,000 per year (current $).  Fifteen of the 116 storms were considered major floods that inundated half or more of the 15,407- acre floodplain.  The largest storm before the construction of the dams occurred in September 1936 and produced a runoff of 5.05 inches over a two-day period that inundated the entire floodplain.

USGS data for the 20 years prior to substantial completion of the project in 1970, indicate significant floods on Sep. 13, 1950; May 19, 1955; May 25, 1957; May 2, 1958; Sep. 8, 1962; Sep. 18, 1964; Feb. 9, 1966; and May 31, 1967.  

                       

         New F.M. 455 bridge over Clear Creek, west of Bolivar, destroyed May 25, 1957.  Courtesy Texas Highway Dept.

 

 

   Highway 51 bridge at Clear Creek, southwest of Era, destroyed by storm on May 25, 1957.  Temporary crossing at far left.

    Highway 51bridge, looking in opposite direction.  Temporary crossing at right.  Courtesy Texas Highway Dept.

 

Subsequent to completion of the dams, significant storms have continued to occur, but have shown a 25-30% reduction in maximum stream flow due to floodwater retention behind the dams and slow release.  Significant post-completion storms peaked on Dec. 10, 1971; July 30, 1973; Oct. 31, 1974; Mar. 27, 1977; May 27, 1981; Oct. 13, 1981; May 29, 1987; May 17, 1989; April 26, 1990; Dec. 20, 1991; and Feb. 20, 1997.  

The largest storm subsequent to project completion, and in recorded memory, occurred over the period October 10 to 14, 1981.  This storm was classed as “catastrophic”, surpassing the Corps of Engineers definition of a 100-year storm for the Clear Creek Watershed.  A Pacific hurricane moved onshore in Mexico, crossed northeast through Mexico and Texas, and stalled over Montague, Cooke, and Denton Counties.  For days it rained, with runoff exceeding the 44,000-acre foot retention capacity of the Clear Creek Watershed flood control system.  While no dams were breached, the water flow was so strong that numerous emergency spillways were significantly damaged.  Secondary roads and culverts throughout the Watershed were washed away.  The damage, while serious, would have been much worse were it not for the enormous volume held back by the dams.  The USGS site on Clear Creek near I-35 south of Sanger indicated a flood gage height of 35.7 feet, and a peak water flow of 104,000 cfs on October 13, 1981.  A 100-year storm event for the watershed is defined as peak flow of  92,300 cfs at this USGS site.  The readings for this storm were almost 6’ higher and 80,000 cfs higher respectively than any previously recorded peak.   

Downstream, Denton suffered, the Lake Lewisville dam was at capacity and monitored closely, and parts of Dallas and areas along the Trinity River flooded, all the way to the Gulf.    Six lives were lost and damage was estimated at $226 million (current $).