Tag Archive for: tunnels

HCFCD Asks for Army Corps Help with Tunnels, Halls Bayou, Addicks/Barker

In June 2022, Harris County Flood Control District (HCFCD) pitched the Army Corps (actually the Assistant Secretary of the Army for Civil Works, referred to as ASA(CW)) for help with three large projects. They included Flood Tunnels; Halls Bayou; and the Addicks and Barker Reservoirs. This leave-behind summarizes the presentation.

Setting the Stage

The presentation begins with a history of the relationship between the Army Corps and HCFCD dating back to 1937. It references past joint projects such as work on the Addicks and Barker Reservoirs; and Brays, White Oak, Little Vince, Cypress, Greens and Sims Bayous.

It also references projects not yet completed such as work on White Oak and Hunting Bayous, and Clear Creek. Finally, it looks forward to future collaboration on Buffalo Bayou, Halls Bayou and a County Wide-Study that “lifts up and empowers our diverse communities to thrive.”

The intro contains graphics that summarize:

  • Damage during Hurricane Harvey
  • Atlas-14 rainfall vs previous estimates
  • Current and Active Army Corps projects
  • A county-wide map of “Recently flooded” (from Harvey) structures overlaid on a social-vulnerability map

The leave-behind then makes three “asks” corresponding with each of the three major projects.

Buffalo Bayou and Tributaries Resiliency Study

The first ask is for help “finding the right solution for Addicks and Barker Reservoirs.” It talks about managing residual risk and liability. Specifically, it asks for support through the completion of the Corps’ Buffalo Bayou and Tributaries Resiliency Study.

It alludes to policies and processes impeding needed progress. Then it says, we must blaze a trail for a new equitable flood risk management paradigm.

An engineer familiar with Buffalo Bayou told me that the study had been cancelled at one time because of a poor Benefit/Cost Ratio. It wasn’t because, as you often hear, that home values were low. It was because land acquisition costs were so high. Possible workarounds: several proposed “innovations” including:

  • Flood tunnels
  • A comprehensive benefits framework that includes more than a strict benefit/cost ratio.
  • “Emphasis on community resiliency, environmental justice, and climate change adaptation.”

The last update of this study on the Corps’ website is from late 2020. The final report has not yet been released. This post from 2020 summarizes the findings of the interim report.

County-Wide Section 203 Study

Section 203 of the Water Resources Development Act was amended to let non-Federal sponsors conduct feasibility studies that serve as the basis for authorization of new water resources projects, such as flood tunnels. But acceptance of the results is at the discretion of the ASA (CW). One objective of the presentation: to get the ASA(CW) to partner Harris County on a County-wide flood risk study.

The county pitched the partnership as:

  • A potential “pilot study for Justice40”
  • Climate change preparedness
  • Empowering vulnerable communities to withstand and recover from flood events.

Justice40 is a Biden initiative, announced within his first few weeks in office. It uses every lever at his disposal “to advance environmental justice and spur economic opportunity for disadvantaged communities. The “40” refers to Biden’s promise to deliver at least 40 percent of the overall benefits from Federal investments in climate and clean energy to disadvantaged communities. One of the priorities: mitigation initiatives that reduce or eliminate the risk of repetitive flooding.

Halls Bayou Section 118 Study

According to the presentation, the Federal government had a project to study flood-risk management on Halls Bayou from 1990 to 2016 when it was “de-authorized.” The county wants to restart it. Section 118 refers to “Pilot programs on the formulation of Corps of Engineers’ projects in … economically disadvantaged communities.”

Harris County wants the Corps to include Halls on its list of ten nationwide pilot studies for such communities. HCFCD points out that Halls has the highest percentage of Low-to-Moderate Income residents of any watershed in the county (71%). Halls has a poverty rate of 28% and a social vulnerability index of 0.85 out of 1.00. Halls also has frequent, severe, repetitive flooding.

At one time, HCFCD cancelled Halls’ Bayou studies because they all came back with Benefit/Cost Ratios below 1.0. That means costs exceeded benefits. HCFCD hopes to restart those in 2022. Section 118 gives the ASA (CW) a way to apply other criteria that compensate for a low BCR in disadvantaged areas.

Posted by Bob Rehak on 7/7/22

1773 Days since Hurricane Harvey

HCFCD Recommends More Study for $30 Billion Flood Tunnels

(Update: Since posting this story, HCFCD has provided a link to the entire 1860-page flood tunnel study online.)

On June 16, 2022, Harris County Flood Control District (HCFCD) held a virtual meeting to present the results of Phase 2 of its flood-tunnels study. Phase 2 recommended eight tunnels estimated to cost $30 billion for further study. The purpose of Phase 3: to advance the design far enough to quantify the benefits and validate cost assumptions in order to apply for grants that would help offset costs.

The secondary purpose of the meeting: to gage public support for tunnels, none of which would benefit the Lake Houston Area.

Below, see a brief summary of the one hour and twenty minute meeting.

Watersheds Where Tunnels Being Considered

Phase 2 recommended additional study for tunnels in the following watersheds:

  • Brays Bayou
  • Buffalo Bayou
  • Clear Creek, Berry and Vince Bayous
  • Halls and Hunting Bayous
  • Little Cypress and Cypress Creeks
  • Sims Bayou
  • White Oak Bayou
From Page 34 of presentation delivered by Scott Elmer, Asst. Director of Operations, HCFCD

The conveyance of all eight projects would TOTAL approximately 75,000 cubic feet per second (CFS). To put that in perspective, that’s approximately 4,000 CFS less than the SJRA released from Lake Conroe during Harvey.

Potential Advantages of Tunnel System

Scott Elmer, P.E. CFM and Assistant Director of Operations for HCFCD, gave most of the presentation. A large part of it focused on the benefits of a flood tunnel system. The hour and twenty minute presentation contained more information than the presentation online. So, I will try to fill in some blanks for you.

Mr. Elmer talked extensively about “inherited flooding.” Much of Harris County, he says, developed before we fully understood flood risk and developed regulations to reduce it. For instance, he showed a series of three images around Halls Bayou and I-45.

  • #1 showed rural farmland.
  • #2 showed development starting near the bayou.
  • #3 showed development so dense that it would require buyouts before mitigation by conventional means.

Mr. Elmer then discussed the time, cost, and disruption of buying out enough properties to construct basins and widen channels. I posted about this last year in regard to the detention basins that straddle Halls at US59. Entire subdivisions had to be bought out before construction could begin. Each of those two basins took approximately a decade to finish, with most of the time consumed by buyouts.

Example of Ideal Location

Here’s an example of another location, farther up Halls between I-45 and Airline Drive.

One of the areas of heavy, repetitive flood damage in Harris County. Image from 1978. Area was farmland in the 1950s.

Many homes in this flat area are no more than a foot or two above the bayou banks. Some even sit below street level.

Same area seen in FEMA’s national flood hazard layer viewer. Cross hatch = floodway. Aqua = 100-year floodplain. Brown = 500-year.

The entire area lies within some kind of flood hazard. And keep in mind, that this flood map was developed after Tropical Storm Allison in 2001. It does not even represent the risk under Atlas 14, the new flood probabilities developed after Harvey.

Harris County’s Flood Warning System shows Halls has come out of its banks at Airline Drive at least 12 times since 1984. Yet there is very little room to widen the channel or build detention basins.

Best Locations for Tunnels

Tunnels represent an ideal complement to traditional solutions in such cases. They:

  • Expand options for flood damage reduction
  • Make the county’s stormwater network more robust
  • Reduce community disruption and increase resiliency

They make the most sense in areas where:

  • Land for traditional solutions is unavailable
  • Residential property acquisition would disrupt neighborhoods
  • Surface solutions would result in environmental impacts

Elmer presented a hypothetical situation to demonstrate equivalent risk reductions. Thirty-four acres required for tunnel construction could offset 3,145 acres of land needed for channel improvements and stormwater basins.

How Tunnel Locations Chosen

In describing how HCFCD chose the eight watersheds for further study, Elmer focused on:

  • Population density
  • Damage centers with high risk
  • Safety of lives
  • Strategic locations for intakes and outfalls
  • Identifying opportunities to integrate tunnels with other flood damage reduction measures
  • Avoiding geologic and man-made hazards, such as oil and water wells; or geologic faults.
Page 33 of Tunnel Presentation

As for the absence of tunnel recommendations on the eastern side of the county, Elmer simply said, other solutions would be more cost effective. He did not provide additional explanation.

For Elmer’s full presentation, click here.

To see a YouTube Video of this entire presentation including the Q&A that followed, click here. The meat of the presentation starts at about 8 minutes and 30 seconds into the video.

  • Elmer’s presentation lasts a little more than half an hour.
  • A moderator describes the need for public comment before September 30 at 41:26.
  • Q&A begins 42:30.
  • The video ends at 1:18:00.

Items Not Covered

HCFCD gave no specific rationales for:

  • Locations of each of the eight tunnels.
  • Excluding large areas of the county.

I, for one, want to read the entire report before submitting my comments. But HCFCD has not made the report available online.

The presenters did not mention current flood risk in the respective locations. Nor did they say whether their recommendations accounted for recent flood mitigation investments.

Since 2000, the watersheds benefitting from the eight tunnels have already received 64 percent of all flood mitigation investments in Harris County. That includes partner spending. For instance:

  • Brays Bayou has received $575.3 million.
  • White Oak has received $526.3 million.
  • Sims Bayou has received $460 million.
  • Cypress and Little Cypress have received $442.5 million.
  • Greens has received $440 million.
  • Hunting and Halls have received $293.7 million.

Full Study Not Released

Before I vote on flood tunnels for these areas, I want to know how much flood risk remains compared to other areas that received less investment.

However, HCFCD has not yet released a study on the level of service (flood frequency likelihood) for every channel in the county.

The Phase 2 study just completed indicates we could spend $30 billion more on 132 miles of tunnels. That works out to almost a quarter billion dollars per mile.

Before I invest that much, I want to know how engineers arrived at these recommendations. Specifically, how much did politics enter into these decisions? The write up on HCFCD’s tunnel page makes it clear that “equity considerations” including the social vulnerability index weighed heavily.

I also want to know how the Cypress tunnel emptying into the San Jacinto West Fork between US59 and West Lake Houston Parkway would affect flooding in the heavily populated Humble/Kingwood Area.

Public Comment Period Lasts Through September 30

If you wish to submit public comments on the flood tunnels, you have until September 30, 2022. Submit comments at Public Input.com/tunnels. I intend to request the entire engineering study and will post more when I learn how HCFCD made the recommendations.

Posted by Bob Rehak

1755 Days since Hurricane Harvey