As growth continues in the Greater Katy area, residents and government officials are grappling with how to balance new developments with efforts to mitigate flooding for home and business owners. Fort Bend County is re-evaluating its drainage criteria for new construction while the city of Katy and Harris County have approved more restrictive development guidelines this year and passed flood bonds in 2018. However, there is worry among some residents that a major development project in Katy has led to an increased flood risk for nearby neighbors.

Residents in the Pin Oak Village and Falcon Point subdivisions said development of the Katy Central Lake contributed to nearly 40 homes flooding in the two neighborhoods—seven in Pin Oak, and the majority in Falcon Point—as well as surrounding areas and over $1 million in property damage during Hurricane Harvey. They are now demanding action from the city of Katy to prevent future flooding.

“We have never had any flooding occurrence, even in the Tax Day floods. We are outside the 500-year flood plain,” Pin Oak Village resident James Schuck said. “In March 2017 they started work on the boardwalk, and in August, Harvey came, and we flooded.”

The Katy Boardwalk crosses over the Katy Central Lake, which was created in 1998 to hold stormwater runoff as part of an agreement between the city of Katy, the Katy Development Authority and Fort Bend County Municipal Utility District No. 37. The boardwalk is part of the Katy Boardwalk Development, which is a major mixed-use project under construction near the Katy Mills Mall that will feature retail, residential and recreational amenities, a hotel and a conference center.

Residents said developers removed dirt from the lake’s top bank and therefore lowered its elevation, or the above-sea-level height of the bank surrounding the lake, which they said contributed to flooding in surrounding neighborhoods during Harvey. Additionally, residents said overflow water was forced into only one spillway located between two berms which then flowed into subdivisions.

Meanwhile, MUD 37’s Vice President Rudy Ammer said the problem lies not in changes to the lake’s elevation but in drainage issues in Buffalo Bayou.

“If Buffalo Bayou is running at flood stage, all the water coming down our ditch and headed to get to Buffalo Bayou isn’t getting in and starts backing up the system,” Ammer said. “And I think everybody agrees that’s the problem, except the injured homeowners.”

Resident concerns

During Harvey, citizens reported water overflowing the detention pond and traveling over the emergency spillway, according to a report conducted by Houston-based engineering  firm Costello, Inc., which was hired by the city to perform an analysis of the Katy Mills Mall detention and outfall system. The report, Katy Mills Mall Drainage Assessment, was published in April and was provided to Community Impact Newspaper by a resident.

According to the report, residents said water was flowing around the north end of the Katy Mills berm as well as flowing into the Falcon Point subdivision. Schuck said an inadequate overflow design forced all overflow into one spillway, which led to excess water flowing into nearby subdivisions.

“If the detention pond had a proper spillway design as required by the Fort Bend Drainage Authority, flooding would have been mitigated,” he said.

He also said developers lowering the bank levels contributed to flooding.

The 1998 agreement between the city of Katy, the Katy Development Authority and MUD 37 states the storm water detention facility should have a top-bank minimum elevation of 130 feet to prevent flooding in the 500-year flood event. A copy of the original contract was emailed to Community Impact Newspaper by a resident.

However, Schuck said drone footage he took before construction shows the elevation at a certain part of the lake to be at 127 feet. After construction, he said footage shows elevation to be only 125 feet at the same location.

Community Impact Newspaper reached out to Costello for comment, but Stephen Wilcox, a project manager for Costello, said their client instructed them to not respond to any inquiries concerning the study.

Seeking a solution

During Harvey, about 40 homes in Pin Oak Village, Falcon Point and surrounding subdivisions flooded, said Alexis Carrico, a Pin Oak Village resident. Carrico said the total cost reported to her by residents was $250,000 in Pin Oak Village and $800,000 in Falcon Point.

Falcon Point resident Pamela Payne  said her home value dropped $100,000 after being flooded by Harvey, and she is experiencing more flooding issues since development began.

“All of our yards are not draining like they used to, and it’s [because of] development,” she said. “I’ve been here 12 years.”

Pin Oak resident Don Ehlert said his home also flooded, and he wants the city to take action, specifically on the gap between the two berms where the spillway sits.

Ammer said MUD 37 is drafting a letter to the city of Katy outlining actions the city can take to mitigate future flooding in the Pin Oak Village and Falcon Point subdivisions, which Ammer said he expects will be finalized and sent in mid-October. MUD 37’s recommendations mostly align with what residents are requesting such as resurveying the area, he said, but also include putting in concrete diverters to force water past houses into the ditch.

“We’re asking the city to go ahead and start making these repairs, which our engineer board member said would be somewhere between $50,000-$100,000 to resolve the problem.”

Ammer said the responsibility lies with the city, not MUD 37, to handle the costs and repairs. The city of Katy did not return Community Impact Newspaper’s requests for comment.

The new norm

Fort Bend County officials also struggle to balance development against flood risk as the definition for a 100-year rainfall event in the Greater Houston area rises.

While the county is not involved with issues pertaining to the city of Katy—those drainage plans are not reviewed or approved by the county—it is conducting its own watershed study and updating its drainage criteria, said Mark Vogler, Fort Bend County drainage district manager.

“We all experienced the big flood of Harvey, but the 100-year rainfall number recently changed, so all this stuff is going have to be calibrated, and the criteria updated,” Vogler said.

The National Oceanic and Atmospheric Administration on Sept. 26 updated its Atlas 14 study, which provides probabilities of rainfall events in Texas. The new analysis redefines some instances of a 100-year rainfall total as a 25-year event for Houston, based on rainfall data for the past several decades, said Mark Glaudemans, an official with the agency’s water prediction office. A 100-year rainfall event for a 24-hour period has increased from 13 to 18 inches around Houston, Glaudemans said.

The county is revising its drainage criteria manual, which controls stormwater release rates from new development to prevent peak flow rates from increasing. The manual has been in place since 1987, Vogler said. Its most recent update was in 2011, according to information on the county website.

Harvey also highlighted the need to plan for storm events that last more than 24 hours and consequently take more time to drain, Vogler said. Current criteria provides for detention for 100-year flood events, but that will be insufficient for storms that last over a period of days, he said.

“It was a four-day event,” Vogler said. “If our detention ponds took four to seven days to drain down, maybe we need to look at longer, multiple-day storm events.”

Additional reporting by Matt Dulin and Rebecca Hennes