CHICKASHA – A federal grant the City Council intends to apply for could pay a significant portion of the estimated $15 million cost of improvements needed to reduce or eliminate flooding in town.
Chickasha, like Guthrie, has a history of floods “that have caused significant damage to properties, infrastructure, and our local economy,” Community Development Director Rachel Bernish wrote in a background memo to the City Council.
City Hall is seeking “a qualified firm to provide professional consulting, planning, design, and construction administration services” for “proactive flood mitigation measures,” Bernish wrote.
The city plans to apply for funding from the Federal Emergency Management Agency’s Building Resilient Infrastructure and Communities program “to implement the recommended improvements from our recent studies,” said Edward Perez, the city’s emergency management director.
One Chickasha family “would have to raise their home 3 feet to remodel it,” Samaniego said. But if the city applied for and received the FEMA grant, and flood prevention measures were implemented, that would get the family out of the flood zone and they wouldn’t have to elevate their house, he said.
Contractors interested in participating in the program were required to submit a notice of intent to City Manager Keith Johnson by 5 p.m. July 23, and a request for qualifications from contractors is due by the end of the day July 29.
Councilman Charlie Burruss was concerned about a provision in the RFQ that requires a consulting firm to use a “Climate and Economic Justice … geospatial mapping tool” in its work. City officials indicated that was boilerplate language used in federal grant applications of this type.
A complete application from the City of Chickasha to FEMA would be due sometime early next year.
If the city’s application is approved, Chickasha might be eligible for a BRIC grant of perhaps $8 million to $9 million, Perez indicated. The city might also qualify for state financial assistance that would be coupled with some local funds, records reflect.
“Flooding in Chickasha is beyond the city’s ability to address alone,” Johnson said.
Multiple flooding studies performed in last 46 years “We’ve kicked this can down the road long enough,” Vice Mayor Georgianne Hebblethwaite said. “We need to move forward.”
A Facebook post from June 2015 – nine years ago – relates, “It appears that the City Council, Mayor and City Manager are all in agreement that it is past time to start the project of protecting downtown from flood. Indications are that an engineer will be hired to see what our options are.”
Multiple studies about flooding in the city have been conducted in the past 46 years, records show.
• In 2015, Chisholm Trail Consulting performed a Downtown Flood Mitigation Study, which identified the stream names that convey storm water runoff in town. That study focused on the removal of bridges in order to mitigate flooding and was primarily a Hydrologic Engineering Center ~ River Analysis System study.
• FEMA conducted flood insurance studies in 1991, 1993, and again in 2012. Those studies were used to determine peak discharges and floodplains in the city.
• Other studies were completed by Smith Roberts Baldischwiler engineers, surveyors and planners, of Oklahoma City, in 2007 (Line Creek east of Fourth Street); C.H. Guernsey in 1995 (Line Creek); Landmark Engineering in 1992 (Congo Creek); HTB and the U.S. Army Corps of Engineers in 1984; and Southwest Engineering (drainage master plan) in 1978.
• Most recently, in 2019-20 SRB prepared a comprehensive “Master Drainage Study” in a three-ring binder that was 2.5 inches thick and packed with data, maps, hydrologic and hydraulic analyses, and myriad statistics about Chickasha.
The master drainage study cost $300,000 and was financed from a 75/25 costshare FEMA grant from the Oklahoma State Hazard Mitigation program. FEMA paid $225,000 and the City of Chickasha contributed $75,000.
History of flooding from sustained rains The City of Chickasha – county seat of Grady County and home of the University of Science and Arts of Oklahoma – is an area of roughly 22 square miles and has a population of approximately 16,500, according to the Census Bureau.
More than one-third of the community is located in a “special flood hazard area,” which results in areas and intersections being routinely closed due to anticipated flooding.
In addition, localized flooding “has been attributed to the condition and inefficiency of the city’s storm sewer system,” SRB wrote. An example of that was the intersection of 14th and Missouri, which was rebuilt last year at a cost of almost $288,000 after the four-way junction was heavily damaged by runoff rainwater that overloaded the drains during a storm May 13, 2023.
SRB developed assessments for 19 watersheds that contribute stormwater runoff, which flows through Chickasha to the Washita River. Individual urbanized watersheds are located within the city, while rural watersheds are located to the west and southwest, SRB noted.
Similarly, stream environments were analyzed “to identify conditions such as erosion problem areas, channel type, floodplain vegetation, FEMA flood zone type, and storm sewer structures and outfalls.”
Flooding blamed on multiple issues Several issues were determined as the cause of stream flooding and erosion at Line and Congo creeks.
• Over time, through construction of the city’s storm sewer system, urbanized flow that historically was conveyed to Congo Creek has been rerouted to Line Creek. In the same way, an unnamed tributary that historically was conveyed directly to the Washita River instead now flows into Line Creek.
Also, other tributaries have been broken due to urbanization, and the time of concentration has decreased for the basins, resulting in runoff getting into creeks and streams faster.
• Inconsistent bridge sizing along Line and Congo creeks means downstream bridges have less capacity than upstream bridges; this has created backwater effects. Furthermore, overtopping of bridges is occurring on roadways, creating driving hazards for the public.
For example, 11 of 13 steel-reinforced concrete box bridges that Congo Creek passes through in Chickasha are undersized “based on hydraulic calculations,” a Hydrologic Engineering Center ~ River Analysis System study determined in 2015 and SRB confirmed in 2020.
• Channel storage is insufficient to effectively convey 100-year flow rates, and channel slopes do not convey flow rates efficiently. These factors cause standing water, decreasing the channels’ storage capacity and leading to stream channel overflow during rain events.
• Erosion and sedimentation was observed in both Line and Congo creeks. Irregular streamflow lines and channel slope can be a major factor creating sedimentation and scour holes along the creeks and streams, SRB reported.