Flood Retarding Structures Prevent Severe Floodwater Damage during June Storms
Story by Randy Henry
The possibility of severe floodwater damage to urban and rural landscapes in Navarro, Limestone, Kaufman, and Hill counties was prevented during torrential storms in June when flood retarding structures (FRS) built by USDA-Natural Resources Conservation Service (NRCS) stored rainfall runoff caused by the heavy storms.
Within the Richland Creek and Cedar Creek watersheds, a series of dams or FRSs, which were strategically placed in all four counties to control rainfall runoff protected communities, infrastructure and families downstream. The dams functioned as designed, and were tested when nine-18 inches of rain hit the two watersheds within approximately seven hours during the storms. Other counties receiving heavy rainfall from the June storms were Henderson and Van Zandt counties.
Navarro County was the hardest hit in the Richland Creek watershed near the southwestern portion of the county in Dawson, Texas, with 10-18 inches of rainfall in approximately seven hours.
"The flooding in southwestern Navarro County could have been far worse without the flood prevention sites functioning as designed in the hardest hit areas of the Richland Creek watershed," said Kristy Oates, NRCS district conservationist for Navarro County. "The heavy rainfall caused major flooding to roads, homes, and agricultural land, yet 28 flood prevention sites retained hundreds of acres of water during the storm event."
Although some of the flood prevention sites received damage to the dams, principal spillways, and auxiliary spillways, they still functioned as designed and successfully to retain any floodwaters from doing further damage downstream.
"We talked to people that have lived in southwestern Navarro County for more than 60 years, and they have never seen flooding like this event before," Oates said.
According to NRCS, a total of 84 FRSs in six counties prevented $5.25 million worth of flood damages from floodwaters to communities, infrastructure, and families downstream. Within the 84 FRSs, 18 dams had auxiliary spillway flows, some over three-feet deep with part of the reduced damages resulting from dams protecting downstream roads. Overall, at least 82 road crossings benefited by the dams holding back floodwaters upstream, including 53 county roads, 20 farm-to-market roads, and nine state roads.
Also, approximately $450,000 in federal funding is being requested through the Emergency Watershed Protection Program (EWP) to repair the damaged FRSs.
EWP provides assistance to project sponsors and individuals in implementing emergency recovery measures to relieve imminent hazards to life and property created by a natural disaster that causes a sudden impairment of a watershed.
If approved, the EWP funding will rapidly help repair three FRS sites as requested by the local sponsors, including the Navarro Soil and Water Conservation District and Navarro County.
The three other counties hit during these storms did not receive any major FRS damage, but sustained infrastructure losses to county roads, bridges, cropland, and fences.
In Kaufman County, three FRS sites in the Cedar Creek watershed had auxiliary spillway flow with none that overtopped from the storms, along with nine FRS sites in Van Zandt County that were impacted by the rainfall. Cedar Creek watershed received 10-14 inches of rainfall within nine hours.
"The FRS dams held during this rainfall event in the Cedar Creek watershed," said Glenn Lubke, NRCS natural resources manager in Forney, Texas.
In addition, Limestone County had five sites that water flowed through auxiliary spillways with two sites overflowing after receiving nine-12 inches of rain in three hours.
Plus, some sites have fences and primary inlets underwater, but still functioned successfully to prevent extensive damage to county infrastructure, loss of life, or local communities downstream.
Hill County was fortunate to not have any FRS site damage, but did sustain infrastructure problems to county roads, cropland, pastureland, and bridges even though it received around nine inches of rain within seven hours.
The FRSs built to protect the areas that stored the floodwater runoff from the storms were approved through the Watershed Protection and Flood Prevention Program by local sponsors with assistance from NRCS.
The program was first conceived in the 1930s when Congress began looking at ways to complement existing downstream flood control programs. Since that time, NRCS has assisted local watershed sponsors in the construction of nearly 2,000 FRSs across Texas.
From this aerial view, Richland Creek dam site No. 14 shows the flood retarding structure (FRS) functioning as designed while retaining rainfall runoff from the heavy storms in June that could have caused damage to surrounding communities and infrastructure downstream. This FRS is located in Navarro County, which was the hardest hit county within the Richland Creek watershed, receiving 10-18 inches of rainfall in approximately seven hours.
With some dams in the Richland Creek watershed overtopping from the heavy rainfall in June, principal and auxiliary spillways like the one shown here at Richland Creek dam site No. 31, played an important role in preventing possible floodwaters from reaching downstream communities and infrastructure in Navarro County.
Never underestimating the power of heavy rainfall is proven with this photo of the damage to the back slope on Richland Creek dam site No. 107B in Navarro County. The torrential storms in June that hit the southwestern portion of the county caused soil damage shown here, yet still retained acres of rainfall runoff protecting nearby downstream communities and infrastructure.
This outlet pipe, center, flowing into the impact basin reflects the large amount of rainfall runoff stored in Richland Creek dam site No. 107B after heavy storms dropped 10-18 inches of water on the county in around seven hours. In the background, notice the soil damage to the back slope of the dam from the storms that hit Navarro County in June.