The Flood Discussion Continues

Two important documents were recently released on flooding in our region.

 

By Bill King
  
The first is the Harris County Flood Control District's (HCFCD) report on Hurricane Harvey written by Jeff Lindner and Scott Fitzgerald, the HCFCD's chief meteorologist and engineer, respectively. The 32-page report is chock-full of statistics, tables and maps that detail Harvey's rainfall and flooding.http://www.hcfcd.org/media/2678/immediate-flood-report-final-hurricane-harvey-2017.pdf A more digestible version of the data is Lindner's PowerPoint presentation. ​http://www.billkingblog.com/wp-content/uploads/2018/06/Brays_Bayou_Association-Harvey-1Jeff-Linder-presentation-abridged.pdf
  
I have asked HCFCD some questions about the report and I will have more to say about it later. But here are a few things that jumped out at me.

Over 70,000 structures that are not in any floodplain were flooded. As I discussed in my previous posts  to review) there were also many areas in the 500-year floodplain that did not flood. This finding further calls into question the utility of the floodplain maps in predicting future flooding.

Over 6,000 homes flooded in the Sims Bayou watershed even though Sims Bayou never came out of its banks. This indicates a failure of the City's systems that convey the floodwater to the bayou. Flooding that results from water attempting to get to the riverine is not shown on the HCFCD inundation mapping tool and is often not reflected on the FEMA flood maps.

Fewer than 500 homes that were constructed pursuant to the County's 2009 guidelines were flooded. 

The Brays Bayou watershed once again suffered the brunt of the flooding, with nearly 24,000 homes flooded. The Buffalo Bayou watershed was second with 17,000 homes flooded.

 

The second document is a report by the engineering firm, Freese & Nichols, on alternatives to reduce flooding around Lake Houston. Most of the report is devoted to the efficacy of adding floodgates to the Lake Houston dam. http://reduceflooding.com/wp-content/uploads/2018/06/Final-Lake-Houston-Drawdown-Memo_-02052018.pdfto 

  
First, the cost of the additional floodgate is estimated at $47 million. The City has said that it has asked (or will ask) for a grant from FEMA to add the floodgates. But the gates could have been paid for more than 20 times from the drainage fees collected by the City since it started collecting them in 2012. City Council just approved another budget which diverts most of the drainage fees to uses other than reducing flooding. The question must be asked of the Mayor and the City Councilmen why is the Rain Tax not being used to take care of Drainage problems as promised.
  
Second, I am becoming increasingly convinced that the I-10 bridges over the San Jacinto River are a critical piece of the flooding in that watershed. The inundation map from the HCFCD below and the satellite photos sure make it look like those bridges are basically functioning like a dam in flooding events. I talked to one person who was in the area during the flood. He said that the water was rushing through underpasses to the west of the bridges with such velocity that it washed out the service road and scored deep trenches.
  
Adding floodgate capacity at the Lake Houston dam will do little good upstream and could cause even more problems downstream if the water cannot get to Galveston Bay because of these bridges. The HCFCD told me there is a comprehensive study currently underway for the entire San Jacinto River watershed. I am not sure when the report is supposed to be finished, but whatever we do in that watershed needs to be coordinated with all of the jurisdictions and entities.
  
These reports highlight the incredible complexity of the flooding problems in our region. We cannot allow that complexity to paralyze us into inaction, but we also need to make sure that the projects we undertake are cost-effective and do not simply move the flooding to a different area.
  
They also highlight that there are no simple, quick fixes to our flooding problems. Flooding in our region is the result of living on a flat coastal, subtropical plain and years of lax regulation and underinvestment in flood control infrastructure. It is going to take years, perhaps decades, of better regulation and increased investment to make a meaningful difference.

 

SAN JACINTO RIVER - BOND PROGRAM

AN INFORMATIONAL PUBLIC MEETING FOR THE SAN JACINTO RIVER WATERSHED RESCHEDULED for June 14th in Kingwood will be rescheduled. PLEASE CHECK BACK FOR THE NEW DATE AND LOCATION.
 The map below shows the approximate location of proposed flood risk reduction projects in this watershed that could be eligible for bond funding. Click on the link below to find you Watershed area and what projects will be done.

​San Jacinto River Watershed Facts

AREA (SQ MILES) POPULATION* STRUCTURE COUNT** HARVEY DAMAGED STRUCTURES***

                                                                                    Area      Population   Structures      Harvey Damage
Inside the 1% (100-year) FEMA floodplain       88.2        14,522          7,543                      2,452
Inside the 0.2% (500-year) FEMA floodplain    17.7        15,676          10,579                    3,641
Outside the 0.2% (500-year) FEMA floodplain 111.3      168,582        90,485                   2,986
TOTAL                                                                          17.2        198,780        108,607                 9,079

*Census 2010, **HCAD 2016, ***HCFCD preliminary count estimates as of January 2018

MEDIAN FAMILY INCOME* $71,000 MEDIAN HOUSE VALUE* $149,000

* 2016 Census Data

If the bond election is successful, projects would be authorized individually for funding by Harris County Commissioners Court. The actual timing of individual projects will depend on a variety of factors including environmental permitting and right-of-way acquisition. Projects will be authorized individually for funding by Commissioners Court, based on recommendations by the Flood Control District.

POTENTIAL PROJECT TYPES
FOR BOND FUNDING


The Harris County Flood Control District accomplishes its mission by working with our partners and local stakeholders to evaluate, develop, and implement flood damage reduction plans and then perform long-term maintenance of drainage infrastructure.

Flood damage reduction plans and projects can include modifications to our streams and bayous to increase the amount of stormwater that they can carry, the implementation of detention basins to store excess stormwater, nonstructural flood mitigation tools such as voluntary home buyouts, and any combination of these methods to address local and regional flooding issues.

Here are several types of projects that may be supported by bond funding:

Voluntary Home Buyouts – The purchase of flood-prone structures from willing sellers in areas that are too deep in the floodplain to benefit from structural flood risk reduction projects, or in areas where flood risk reduction projects are not feasible.  This process includes the demolition of the structure and relocation of the seller to higher ground.

Storm Repair – Major maintenance projects that restore the designed function and capacity of a channel or stormwater detention basin.

Subdivision Drainage Improvement – Partnership projects with the Harris County Engineering Department and a Municipal Utility District to provide drainage improvements to subdivisions in unincorporated Harris County.

Partnership Projects – Flood risk reduction projects such as channel modifications or stormwater detention basin construction using a combination of Harris County Flood Control District funding and funding from local, state, or federal partners such as the Federal Emergency Management Agency.

Local Projects – Flood risk reduction projects such as channel modifications or stormwater detention basin construction using ONLY Harris County Flood Control District funds.

 

Houston City Council adopts stricter flood plain development rules

By Rebecca Elliott

Houston City Council agreed Wednesday to require new homes built in the flood plain be elevated higher off the ground, the Bayou City’s first major regulatory response to the widespread flooding Hurricane Harvey unleashed last August.

The vote marks a shift away from Houston’s longtime aversion to constraining development, and means all new construction in the city’s flood plains will have to be built two feet above the projected water level in a 500-year storm.

More than three hours of contentious debate preceded the unusually tight 9-7 vote, which largely fell along party lines.

“This is a defining moment,” Mayor Sylvester Turner said in his final pitch to council. “Can we undo what was done with Harvey? No. But can we build looking forward? Yes. Does it mean it may cost more financially? Yes. But if it has the probability of saving lives, and if it has the probability of letting people know in our city and those who are looking to come to our city that we are taking measures to be stronger to be more resilient, then that’s positive for the city of Houston.”

Council members Karla Cisneros, David Robinson, Dwight Boykins, Ellen Cohen, Jerry Davis, Robert Gallegos, Amanda Edwards and Dave Martin joined Turner in backing the changes. Council members Mike Knox, Jack Christie, Brenda Stardig, Michael Kubosh, Steve Le, Greg Travis and Mike Laster opposed the regulations.

The new rules take effect Sept. 1 and apply to all new buildings within the 500-year flood plain, which is deemed to have a 0.2 percent chance of being inundated in any given year.

Current regulation mandates that buildings be constructed one foot above the flood level in a less severe 100-year storm and apply only within the 100-year flood plain, where properties are considered to have a 1 percent annual chance of being inundated. This will be the first time Houston is imposing minimum elevation requirements within the 500-year flood plain.

 

City report backs flood plan
Council to weigh building rules sought by Turner
 

No decision was made as to Building Codes last week at the meeting. Supposedly they will make a decision this week. Decisions need to be made and be made soon or all construction in the city will come to a halt.


By Mike Morris

Mayor Sylvester Turner says thousands of homes would have been spared flooding during Harvey under his new proposed building rules. Builders say those changes would be too costly.

More than 80 percent of the homes in Houston’s flood plains that were damaged by Hurricane Harvey would have been spared if they were at the higher elevation that Mayor Sylvester Turner has proposed for future development in those flood-prone areas.

That figure was among the data contained in a new Houston Public Works analysis of Harvey’s wreckage as council members weigh a rewrite of the ordinance governing the city’s flood plains. City Council is expected to consider the new rules next week and to discuss them at a committee hearing Wednesday.

The 73-page report’s release to council members and the public comes seven weeks after Turner first outlined his proposal and more than a week after the end of the city’s announced period for public feedback.

Among the report’s key findings:

•Of the 31,822 flooded single-family homes Public Works examined in city flood plains, about half would not have flooded during Harvey if they had been built to the city’s current elevation standard, which requires new or redeveloped homes to sit at least 1 foot above the projected water level in a 100-year storm. Placing the homes 2 feet above the projected 500-year flood level — the standard Turner is proposing — would have spared 84 percent of the homes.

Although more than 47,000 single-family houses located in the city’s flood plains took on water during Harvey, the city left about a third of them out of that analysis because it did not have complete data on water or elevation levels for those properties.

A 100-year storm is one that has a 1 percent chance of occurring in any given year; a 500-year storm has a 0.02 percent chance in any year.

•Of the more than 101,000 structures in the 100-year flood plain, 30 percent were damaged during Harvey, as were a third of the more than 86,000 buildings in the 500-year flood plain. Of the roughly 469,600 structures outside of a mapped flood plain, 19 percent were damaged.

•More than 13,000 homes meet the current elevation standard, which applies only within the 100-year flood plain. About a third of them flooded during Harvey.

•About 8,500 of the 38,000 new home permits in Houston in the past decade were for homes in flood plains. Those properties, on average, are valued at $388,144, about a tenth less than the citywide average for homes built at that period.

Builders, developers, civic leaders and council members said the study provided helpful context, but few said its findings swayed their views. In general, industry groups said the data did not address their concerns that the city’s proposal is too strict, while neighborhood groups questioned why the city is not moving more quickly to bolster all of its flooding regulations, not just those in risky areas.

Councilman David Robinson, who chairs the infrastructure committee, said the data made him more comfortable with the proposed changes, particularly the elevation requirement.

“No one at all that I know is questioning that things have to be adjusted. That’s easy. The challenge is figuring out what is the right threshold,” Robinson said. The report, he said, shows that anything over the proposed elevation of 2 feet above the 500-year flood plain “emerges as the point at which there’s a significant diminishing return, and for that reason I find it quite satisfying that we are apparently paying attention to our numbers.”

Greater Houston Builders Association CEO Casey Morgan said the changes essentially would mandate pier-and-beam foundations in flood plains, adding $32,000 to the cost of a home, according to GHBA estimates.

That price jump would price out thousands of families, Morgan said, and preclude builders from producing cheaper housing in transitional areas.

Houston Real Estate Council representative Suzy Hartgrove said the changes also would complicate commercial developers’ decisions on whether to rebuild “obsolete” retail centers. Rather than paying to rebuild higher and risk steeper rents driving away tenants, she said, owners simply will repaint or replace the facade.

“We’re trying to find a balance between more stringent regulations — because we agree homes need to be built higher — but so it’s not sort of this one-size-fits-all standard across the flood plain, and maybe even across the city,” Morgan said.

City officials countered with estimates showing a pier-and-beam foundation would cost $11,000 more than a slab-on-grade.

Ed Wolff, a Houston Association of Realtors leader, said council should force homes in the 100-year flood plain to be built an additional 1 foot higher immediately, then further study what to do within the 500-year flood plain.

“It’s easy to say, ‘We want to make a change.’ It’s hard to understand what that impact would be in each individual location,” he said. “Our goal is just not to have to revisit the ordinance 18 months from now because we’ve completely put a stop to development in the flood plains and have properties being built at 15 feet high.”

One fix, industry groups said, would be for the city to alter its proposal to force builders to remove a shovel of dirt for every shovel of dirt they bring to a site. This “no net fill” rule already applies within the 100-year flood plain, and the proposal would extend it to the 500-year flood plain.

Allowing builders to add a limited amount of dirt to properties in the 500-year flood plain, builders said, would increase the portion of homes that could be built on elevated slabs instead of piers.

The local American Council of Engineering Companies, in a letter to council members, said fill dirt should be allowed in the 500-year flood plain because the stormwater it would displace would be “very small in relation to the overall storage volume” within that area.

Turner, at a west side community meeting Monday, touched on elevation and fill in defending the proposal to some skeptical residents. “For future construction, I think it’s critically important that we use the 500-year flood plain as our guide and we go (2 feet above that)” he said. “It’s important to build higher and to do it in such a way that you do not flood your neighbor, and that’s why we do not allow fill.”

Neighborhood leaders also disagree with industry groups on the issue of fill.

The Super Neighborhood Alliance, a coalition of civic clubs, supports the decision to extend regulations from the 100-year to the 500-year flood plain, but said the city should explicitly mandate pier-and-beam construction because the city will not effectively enforce the “no net fill” rule.

The alliance, in a statement its members adopted last week, also said the rules should be changed in concert with other sections of the code related to drainage.

Jim Blackburn, founder of the Bayou City Initiative, a collection of civic groups focused on flooding and drainage issues, echoed that point. Blackburn said the response he has heard from his members is that the mayor’s proposal is not broad enough.

“I’ve had email after email complaining about the fact that this is really such a low bar for the city to start with,” he said. “It’s absolutely crystal clear our 100-year flood plain is obsolete. It’s important for them to do it, but I think they could have gone much further, and should have.”

Half of all Harvey damage occurred outside mapped flood plains, he noted, which the proposed changes do not address. City officials have said they plan to advance regulatory updates on that issue and others to council in the coming months.

“It’s time for the industry groups to get on board with what it’s going to take to make Houston resilient in the 21st century,” Blackburn said.

“If the industry groups end up being the impediment to progress, that’s no way to go forward.”

In addition to not being swayed by the report’s findings, however, some industry representatives questioned the validity of the data.

The release of the data two months after the proposal was announced also bred suspicion.

“The mayor started with 500-plus-2 and he said, ‘Y’all go figure out how we make that make sense,’” Wolff said.

The report states that data analysis began in September and preliminary conclusions were reached in December. Additional data “continued to be collected and analyzed through early March,” the report states.

Turner has said city leaders “suspected” their chosen standard was the right one based on preliminary work, an assumption that was “confirmed by the data. And as we continue to crunch the numbers, we’ll continue to make that data available.”

The city identified almost 59,000 buildings in some way damaged by Harvey in city flood plains, homebuilder Mike Dish-berger said, but studied the depth of flooding in just 31,822 single-family homes to estimate what effect the proposed elevation rules would have had.

“You can manipulate the data any way you want,” he said. “If you know the outcome needs to be this, I’ll pick 31,000 homes and not 35,000 homes to investigate.”

Public Works officials pushed back on that characterization.

A third of the 47,745 single-family homes flooded in city flood plains were not studied, they said, because there was no recorded water line showing the depth of flooding, the Harris County Flood Control District did not have data on the elevation of the home’s first floor, or both.

“No homes were excluded that had both recorded high-water marks and finished floor elevation data,” said Public Works spokeswoman Alanna Reed. 

 

 

 

 

 

 

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