How County Bond Funds Could Leverage Additional Dollars

Early voting for the $2.5 billion Harris County Flood Bond Referendum begins August 8. If approved,  the County could leverage that money to increase the amount available for flood mitigation. Matching funds from FEMA, HUD, the State, and other sources are available. These grants usually operate on a 75/25 or 90/10 basis, returning $3 to $9 for every dollar put up.

Local Dollars Leverage Matching Funds

If voters approve the $2.5 billion referendum, the bond funds could potentially bring in billions of additional dollars. Here is how funding for Flood Control District projects works. (For a printable PDF, click here.)

Partnership Matching Funds Available for Harris County Flood Control District Projects

Bond money can be used as “seed money” for some types of projects. It qualifies us to receive additional money in the form of grants from other partners such as the Federal Government, State, Coastal Water Authority or the City.

Federal dollars for Harvey flood mitigation efforts are available now, but may go elsewhere if we don’t act. Every city along the Gulf Coast is competing for available matching funds.

Partnership Projects: More Leverage but Less Control

Even though you may not be able to follow all the ins and outs of the diagram above, you should be able to see that many opportunities exist to extend the impact of our own dollars. That’s the good news. The downside is that when you start spending other people’s money, they want to have a say in how you spend it. It’s important that we understand risks as we move forward. To get more money, we must give up some control.

Q: How will projects in the bond proposal be selected and prioritized?

A: Harris County Commissioners Court directed Flood Control District staff to develop list of projects. This is not an exact list of projects that must be or will be built with bond proceeds. It represents a list of projects that would meet the goal of the bond election, which is to both assist with recovery after previous flooding events (including Harvey) and to make our county more resilient for the future.

High on the priority list are construction-ready projects with federal funding partners (such as the U.S. Army Corps of Engineers and the Federal Emergency Management Agency) that give the County “the most bang for its flood control buck.”

Q: Can the bond money be used for purposes other than flood risk reduction?

A: No. Under Texas law, bond funds in this election could only be used for the purpose approved by the voters. Bond funds will not be used to fund additional staff positions at the Harris County Flood Control District.

Q: Do bond proceeds have to be used for the specific projects recommended by the Flood Control District?

A: No. Voters will be asked to authorize bonds for flood damage reduction projects, but specific projects may be added to the list of potential projects in the future or projects on the list could be modified based upon public input.

However, officials can only spend bond money on projects supported by the Bond Language. Voters will not be voting on a specific project list, only on the language in the proposal.

Freeing Up Budget to Improve Maintenance

Maintenance is NOT in the bond proposal. Nevertheless, the bond could still improve maintenance in a roundabout way. Here’s how. About half of the Flood Control District’s current $120 million per year budget goes to capital expenditures. If approved, the bond would free up about $60 million currently focused on construction projects.

The other $60 million in the Flood Control District’s budget is devoted to Maintenance and Operations. It is roughly divided as follows: $30 million for salaries and overhead; $10 million for mowing; and $20 million for maintenance.

That $20 million currently devoted to maintaining ditches, bayous and streams, if added to the $60 million that is freed up, would make $80 million that could be devoted to improving maintenance. That means the District’s maintenance budget could quadruple.

Yea or Nay?

On balance, I like how the bond is shaping up and I trust the people in charge of it. I wish that the $50 million allocated for a dredging partnership project was a dedicated $50 million. Then, if the bond proposal passes, we might be able to get the Army Corps to extend the scope of their current dredging to include the giant sand bar at the mouth of the West Fork. Addressing that issue as a change order to the current contract could save years, save dollars, and reduce risk immediately.

Posted on June 23, 2018, by Bob Rehak

328 Days since Hurricane Harvey

How Floodplain Mining Can Lead to River Capture

In a previous post, I showed satellite and aerial images of water sweeping through a West Fork sand mine complex during Harvey. This is part of a process called river capture. In the photo below you can see the West Fork flowing into and through mines on both sides of the river during Harvey.

Dikes on both sides of the river were breached in the process. In fact, historical images in Google Earth show that they have been breached repeatedly.

During Harvey, floodwaters swept through this complex and breached dikes in multiple locations as the river took a shortcut through the mines. 

Highest Risk Scenarios for River Capture

A review of scientific literature reveals that the risk of stream diversion through pits (river capture) is increased by:

  • Proximity of pits to the river
  • Increased depth of the pit, particularly where the base of the pit is below the lowest part of the river.

The phenomenon seems common and the consequences well documented.

2014 Survey of Scientific Literature Finds 37 Examples

In 2014, Anthony Ladson and Dean Judd, two Australian researchers, found 37 instances of river capture in a review of scientific literature. They published their findings at the Seventh Annual Australian Stream Management Conference in a paper titled A review of the effect of floodplain gravel mining on river stability.

Advanced economies, they say in their introduction, require large amounts of aggregate (sand and gravel) to sustain growth. Aggregate makes up 80% of concrete and 90% of asphalt pavements. 

Many see floodplain mining as a safer way to obtain this aggregate than in-stream mining, but floodplain mining still poses substantial threats to river stability.

Dangers of River Capture

As we saw on the West Fork of the San Jacinto during Harvey, floodwaters take a shortcut through mines that are built on point bars inside meander loops.

Sand bars within sand mine, caused during “river capture” of the mine. These bars prove sand was carried downstream. This photo taken on 10/28/2018 (after Harvey) also shows repairs to mine wall. During floods, the river tries to cut across meanders, runs through the mines and carries sand downstream.

The authors say this can lead to:

  • River bed degradation
  • Bank erosion
  • Channel widening
  • Infrastructure damage or destruction
  • Loss of riparian vegetation
  • Habitat damage
  • Degradation of water quality.

Their review of local, national and international case studies showed that pit capture and subsequent river channel changes, are a common consequence of floodplain mining.

Changing River Environment and Putting Infrastructure at Risk

In their conclusion, Ladson and Judd state, “Although floodplain gravel mining has been considered a safer option than the direct extraction of gravel from a river, substantial risks to river stability and river health values remain. Floodplain gravel mining can cause change in the riverine environment, both locally and distant to the mining site, and in the short and long term.” 

“There are substantial risks to infrastructure if river diversions occur which trigger bed and bank erosion.” 

“There may be a role for river management agencies to influence the amount of mining that is undertaken, and the manner in which it is undertaken, in order to mitigate these threats.”

Mechanisms of River Capture

Another study goes into more detail. This second study, was conducted by Jacobs Engineering in 2015, also in Australia. It describes the processes behind river capture, the risks, and how to reduce them. It is titled Risk_assessment_of_floodplain_mining_pits_in_the_mid-Goulburn_Valley, The Golburn River, like the San Jacinto, meanders through relatively flat land. It also has approximately the same number of sand mines that the San Jacinto has.

Jacobs identified three risk scenarios for river capture:

  1. Lateral migration of river channel into the pit
  2. Sub-surface piping into pits and subsequent failure of pit walls
  3. Flow of water into and through the pit and subsequent erosion of the buffer strip between the channel and the excavated pit.

Some San Jacinto Mines Push Recommended Safety Margins

Jacobs assesses (page 19) that 100 meters is the minimum setback to prevent river capture from occurring. In some places on the San Jacinto, dikes are less than 15 meters wide.

Jacobs also assesses that river capture is almost certain (page 19) where the basement of the pit is more than 5 meters lower than the river. San Jacinto sand miners are mining at more than double that depth.

“The physical processes of pit capture have been well documented from case studies: incision upstream and downstream of the pit are expected, with bed adjustments continuing until the river establishes a new equilibrium and grade,” says Jacobs.

Ways to Mitigate Risk of River Capture

Jacobs identified two main ways (page 47) to reduce this risk:

  • Locate pits out of the 100-year floodplain
  • Implement controls such as levees, grade-control structures, pit setbacks, depth limits, and waterway diversions.

Sadly, all sand pits on the San Jacinto are already in the 100-year flood plain. Worse, all but one are at least partially in the FLOODWAY, which is defined as the main channel of the river during a flood.

Even more sadly, it appears that none of the measures in the second category are being applied to San Jacinto mines either.

Posted by Bob Rehak, July 22, 2018

327 Days since Hurricane Harvey

More Dredging Now Officially Included in Project List for Flood Bond

The Plea for DDG has paid off. More detention, dredging and gates are now all officially listed as projects for Harris County’s historic, $2,5 billion, flood-bond referendum. Why detention, dredging and gates? Less in. More through. Faster out. The flood mitigation trifecta.

Looking south toward King’s River Estates at the mouth bar blocking the West Fork. This bar is why we need more dredging. The Army Corps will not be removing it. However, it likely backs up water for several miles and increases the rate of sedimentation in the Humble/Kingwood corridor by slowing the velocity of the river.

At the San Jacinto Watershed meeting held on July 10th, many people were told that dredging would NOT be allowed under the bond. Evidently, some county employees did not get the message that it would be included and they gave residents mixed signals.

From Confusion to Clarity

I addressed this confusion in an earlier post, but some residents were still skeptical when they didn’t see dredging on the approved project list. Now it’s on the list which has been officially updated. We can breathe a sigh of relief.

This new list of bond projects clearly breaks out dredging as a separate item and allocates $50 million to it.

Projects for the San Jacinto Watershed are listed on pages 8 and 9. See the last item on page 8. The description of the line item pertaining to dredging says, “Potential partnership project with the City of Houston, Coastal Water Authority, and the State of Texas to permit, design, and complete dredging of the East Fork, West Fork and Lake Houston area waterways to reduce flooding risks.”

Watershed-Wide, Integrated Approach

Note that some projects which benefit us may also be listed upstream in tributary watersheds. Examples: additional detention in Montgomery County, far western Harris County along Cypress Creek, or another location TBD based on the outcome of the San Jacinto Watershed study (which is currently stalled because of lack of funding). The bond could help get that moving, too.

Ditches, Buyouts also Included

Note also that we got more than dredging, detention and gates. If this bond passes, it includes money that will also help improve drainage ditches and buy out homes that flood repeatedly.

What does this mean? In my opinion, it means the Lake Houston area can stop worrying about whether there are projects in the bond that will benefit all of us as opposed to some of us. We can now evaluate the bond on its costs and benefits.

Two Types of Allocations

Each project on the list falls into one of two categories. The first includes projects that will be fully funded directly by bond money. The second includes partnership projects. In the latter category, bond money represents only a percentage of the total cost. For example, bond money might be the seed money to qualify for matching grants from other governmental bodies.

While partnership projects can take longer to get off the ground and have a higher degree of uncertainty surrounding them, ultimately they leverage more local dollars. Depending on the number of partners and the formulas applied, one dollar could turn into four or more.

Total money allocated for San Jacinto Watershed projects exceeds $320,000,000 when matching funds are included. The massive turnout for the Bond meeting at Kingwood Park High School paid handsome dividends.

We can now take this discussion to the next level.

Posted July 20, 2018 by Bob Rehak

325 Days since Hurricane Harvey

Clock Starts Ticking on Army Corps Dredging Project

Officials from the U.S. Army Corps of Engineers (USACE) announced yesterday afternoon that representatives from Great Lakes Dredge & Dock Company, LLC of Oak Brook, IL, met with Corps’ contracting and project managers for a pre-construction conference. The meeting finalized project requirements for the $69,814,060 dredging and debris removal emergency operation and the clock has started ticking on the project.

The easterly limit of the U.S. Army Corps’ emergency dredging project on the West Fork of the San Jacinto.

The FEMA-funded project covers about two miles of the West Fork of the San Jacinto River near the West Lake Houston Parkway and Lake Houston. FEMA guidelines limit the operation to restoring pre-Harvey conditions.

Beginning of First Phase

“This is the beginning of the first phase of a very challenging project,” said Al Meyer, a USACE Galveston District administrative contracting officer.  “This project involves dredging and debris removal of 1.8 million cubic yards of sediment that has contributed to recent flooding in that area.”

The Focus for Next Week

He said the community should start to see activity within the next two-weeks. According to Corps Colonel Mark Williford, next week  teams will be engaged in:

  • Pre-dredge hazard surveys
  • Before-cut surveys
  • Disposal-area surveys
  • Staging-area set up

Meyer, a professional engineer with more than 35 years’ experience with the Corps, says the conference allowed project team members to interact with Great Lakes representatives to ensure a complete understanding of contract requirements.

“The clock starts today; our contractors have 270 days to complete the project that will work to reduce, but not eliminate flooding, and return the area to pre-Harvey conditions.” said Meyers.

Less than 4 Months from Survey to Dredging

This will be one of the first projects initiated as a direct consequence of Hurricane Harvey.

Corps surveying began in April to determine sediment levels within the West Fork of the San Jacinto River after FEMA responded to a State of Texas request under the Stafford Disaster Relief and Emergency Act of 1988. Since then, the Corps has developed models based on their survey findings, evaluated several different dredging plans, finalized specifications, bid the project, vetted the bids, awarded the job and started mobilizing for it.

The USACE Galveston District was established in 1880 as the first engineer district in Texas to oversee river and harbor improvements. The district is directly responsible for maintaining more than 1,000 miles of channel, including 250 miles of deep draft and 750 miles of shallow draft as well as the Colorado River Locks and Brazos River Floodgates.

Posted 7/19/2018 by Bob Rehak

324 Days since Hurricane Harvey

County Position on More Detention, Dredging and Gates for Flood Bond

Today, I received feedback from Harris County on adding “more detention, dredging and gates” (Plea for DDG) to the upcoming flood bond referendum. The good news: Additional dredging, detention and gates will be achievable within the bond. The bad news: based on the feedback, there is still one hurdle to clear: finding partners to share dredging costs.

The mouth bar where the West Fork meets Lake Houston. Fosters Mill and King’s Point are in the background.

Background on Plea for DDG: Detention, Dredging and Gates

You may recall that RecoverLakeHouston, the Lake Houston Area Chamber, and the Lake Houston Area Grass Roots Flood Prevention Initiative (as well as I) all lined up to support the Plea for DDG. The idea: during floods, more detention, dredging and gates would reduce input, increase throughput and speed up output.

Giant Turnout

The community turned out in force to support the initiative. The response literally overwhelmed county officials at the meeting. Seven to eight hundred people attended, making it the most attended of all the watershed meetings to date. Typically, meetings have been drawing one to two hundred people according to those who have attended multiple meetings.

Because of the large number of attendees in Kingwood and the open house format, many people felt the meeting was somewhat chaotic. Worse, some attendees received feedback from a small number of the county employees who mistakenly told them that dredging was NOT possible under the bond.

Clearing up the Confusion

I received this email from the county today. It clarifies their position on all three requests:

Thank you for your input in support of #PleaForDDG for the San Jacinto River watershed.  Your submission has been recorded and considered by the Harris County Flood Control District staff.

With regard to drainage improvements for the the San Jacinto River watershed, the Flood Control District is partnering with Montgomery County, the City of Houston and the San Jacinto River Authority to determine short-term and long-term improvements, such as:

  • Expanding the Flood Warning System (http://www.harriscountyfws.org) into Montgomery County to include new rainfall and stream level gages
  • Improved coordination between the two county Offices of Emergency Management during disasters
  • A vegetation and sediment management plan with the goal to reduce the amount of silt and sand eroding into the river
  • Regional mitigation projects such as river dredging, buyouts and detention basins

Dredging to restore the San Jacinto River and Lake Houston

On July 6, 2018, the US Army Corps of Engineers awarded a contract to Great Lakes Dredge and Dock, in the amount of $69,814,060 to remove sediment and debris resulting from Hurricane Harvey from the West Fork of the San Jacinto River. The Bond Program does include funding that could provide a portion of the cost share for any future dredging work on the East Fork/West Fork/Lake Houston area. Any future dredging project would have to be a collaborative effort between the City of Houston, the Coastal Water Authority, and possibly the State of Texas. At this time, no details have been worked out on future dredging. The Flood Control District will update the Bond Program maps to indicate another Partnership Project (green cross symbol) within the San Jacinto River watershed exhibit noting East Fork/West Fork/Lake Houston Dredging. The description will be “Potential Partnership Project with the City of Houston, Coastal Water Authority, and the State of Texas to permit, design, and complete dredging of the East Fork/West Fork/Lake Houston area waterways to reduce flooding risks.” The dollar amount will be shown as $50M from Harris County Flood Control District and TBD (to be determined) for the City of Houston, the Coastal Water Authority, and the State of Texas. The Flood Control District cannot commit nor obligate other agencies to allocate funding due to the fact that there is no agreement in place for the dredging project.

Detention/Sediment Basins West and North of Highway 59

These improvements are included in the list of potential projects within the bond program (see local projects F-88, F-14, and F-15 which will be used for Planning, Right-Of-Way Acquisition, Design and Construction of General Drainage Improvement along the San Jacinto River and Cypress Creek west of Highway 59). For drainage improvements north of Highway 59, the Flood Control District is coordinating with Montgomery County on a watershed study to investigate flooding problems and identify where detention basins could best serve to reduce flooding risks along the San Jacinto River.

Tainter Gates on Lake Houston Dam

On July 10, 2018, as a result of the community input process, the Flood Control District has added a Partnership Project (green cross symbol) to the list of potential projects within the bond program for the design and construction of additional gates. The partners would be the City of Houston and the Coastal Water Authority since they are the entities that have jurisdiction over the lake and the dam structure; our agency does not. The Bond Program could, however, provide partial funding of up to $20M for this effort.

When considering project ideas suggested by the community, the Flood Control District will prioritize projects that meet its mission to provide flood damage reduction projects that work, with appropriate regard for community and natural values. You can learn more about the project ranking criteria on our website: https://www.hcfcd.org/bond-program/community-input/

Thank you again for sharing your input. The bond election will be held on August 25 with early voting on August 8.

After reading this, I emailed Harris County Flood Control for one more clarification. Was spending $50 million on dredging contingent upon finding partners to share the cost? The answer: Yes. Fifty million, they say, is not sufficient by itself to do the dredging necessary.

So Where Does that Leave Us?

Additional gates for Lake Houston seem to be within scope and well supported.

More upstream detention seems to be within scope and also well supported. However, before any action can take place, the San Jacinto Watershed study must be completed. It is rumored to cost around $2 million and has been awaiting funding since late March. Presumably, the County’s share of the funding would come from this bond if it passes. The study would take a year or more to complete.

No one can say at this time what the study’s recommendations would be. So there is some uncertainty surrounding the request for more upstream detention. Please note, however, that other groups further upstream, for instance on Cypress Creek, are also requesting more upstream detention. My feeling? If the bond passes, more upstream detention is very likely. However, of all the projects, detention would take the longest to complete because it involves identifying and acquiring land.

Finally, additional dredging is also within scope and well supported. However, dredging has the highest degree of uncertainty associated with it because it will require partners who have not been approached and who have not committed any dollars.

To reduce uncertainty surrounding dredging before the bond, we would likely have to obtain commitments from one or more other stakeholders who are mentioned in the email above.

Recommended Next Steps

Before the bond referendum, area leaders need to actively seek support from those other stakeholders and communicate the outcome so that voters can make informed decisions about their votes. Of all three measures, dredging could be implemented the quickest.

In the meantime, residents should continue to submit their requests for more detention, dredging and gates. A groundswell of support will help send a message to the county’s potential partners.

Posted July 17, 2018 by Bob Rehak

322 Days since Hurricane Harvey

Sediment Plume from Above the Storm

Looking back to the period immediately after Harvey, check out this NASA photo of a sediment plume coming out of Galveston Bay on 8/31/2017. An astronaut took the photo using a Nikon D4 with a wide angle lens from 216 miles above the Earth.

As Harvey moved away from Houston, note the sediment plumes spilling out of bays in this photo of the Texas Coastline.

Talk about a dredging problem! The entire northern Gulf of Mexico looks like a Mint Oreo Shake. The brightest part of the plume coming out of Galveston Bay in this shot of the Texas Coastline measures 20 – 30 miles offshore. But the faintest part of the sediment plume extends approximately another 80 miles. Houston is northwest of the bright, light brown area under the clouds that form an arrowhead in the middle of the photo.

Zooming in and boosting contrast. We can see Lake Houston above Galveston Bay on the right of the clouds in the middle.

The mind boggling thing is that enough pressure existed to push the plumes out that far that fast.

Technical Data

NASA PHOTO ID iss052e078795.NEF
GMT 2017:08:31 19:23:43
MODEL NIKON D4
Shutter 1/500
Aperture 18.0
ISO Speed 400
Focal Length 24.0 mm
Lens ID AF-S Nikkor 17-35mm f/2.8D IF-ED
Compensation           -1/3
Mission: ISS052 Roll: E Frame: 78795
Country or Geographic Name: USA-TEXAS
Features: HURRICANE HARVEY, HOUSTON, GALVESTON B., MATAGORDA B., FLOODING, DRAINAGE
Center Point: Latitude: 29.0 Longitude: -95.5 (Negative numbers indicate west for longitude)
Spacecraft Altitude: 216 nautical miles
Sun Elevation Angle: 65 (Angle in degrees between the horizon and the sun, measured at the nadir point)

Posted on 7/14/2018 by Bob Rehak

319 Days Since Hurricane Harvey

Photo: Courtesy of NASA

Need for Sediment Management Planning

Sand and sediment clog our rivers and lake. “Dredge!” you say.

“Not that simple,” say the experts. “Who will pay for it? How much should we dredge? Where will the sediment go?”

That’s why we need planning for sediment management. We need to dredge the worst parts of the river now; the U.S. Army Corps of Engineers (USACE) has already started that as an emergency project. But we also need to dredge other parts of the river that are not quite critical yet. And we need to figure out how to do all this on a regular basis so that it never gets this bad again.

A giant sand dune has formed at the mouth of the west fork of the San Jacinto. It is not being addressed by the Army Corps dredging project but should be. Thousands of homes upstream from this massive blockage flooded during Harvey.

Sediment Management Challenges That Lie Ahead

I have talked about these issues with experts from Harris County Flood Control and USACE. Both say planning is crucial to a successful maintenance dredging/sediment management program. One provided this document: Galveston-Bay-Programmatic-RSM-Plan-Rev-1, as an example of what we need for the San Jacinto. It’s a long document – 112 pages. But it is worth reading the executive summary, introduction and table of contents at the very least. Parts of it discuss the upper reaches of the San Jacinto. But the main value it provides is that it outlines the challenges ahead.

  •  Who will lead the effort? Who will support it?
  • How much money is needed per year? How can we budget for it? Who will share in the costs?
  • Where will the dredged materials go? How can we identify opportunities to reuse and sell them? Who will market them and how? To what extent can sales defray dredging costs?
  • What are the true life-cycle costs of the sand and sediment that miners send downstream to us?
  • How can we reduce their contribution to the problem? Is there a way to make them part of the solution?
  • How can we coordinate upstream and downstream efforts so that the entire river system flows freely?
  • How can we remove channel blockages more quickly after floods to help prevent additional flooding?

All of these are difficult questions. Starting such an extensive program is like starting a new business.

Budgeting Comes First

A business plan and budgeting are the first issues we need to address. Where will the money for all this come from? Without answering that first, everything else is moot.

So who are the stakeholders?

  • City of Houston – Ensuring the future of Lake Houston is essential to ensuring the future of the City. It’s the City’s main source of water.
  • Harris County Flood Control – Half of the people that live in the county, live in the City.
  • San Jacinto River Authority (SJRA) – The State created the Authority back in the 1930s to impound water and protect people from flooding. Those missions were recently reconfirmed by the Governor.
  • Coastal Water Authority – CWA is the contract operator for Lake Houston Dam and Reservoir. They sell water just like SJRA and can raise money thru water rates to fund flood mitigation. Their enabling legislation mentions drainage and flood responsibilities – same as SJRA.
  • State of Texas – This region has a quarter of all the people who live in the state. Nuff said.

Expecting all costs to be covered by the Harris County Flood Bond in perpetuity is just wishful and foolish thinking. The bond is for capital projects, not ongoing maintenance. You might be able to justify the first dredging as “channel improvements.” But after that, for the sake of the community, we need to find a way to make this program sustainable. Paying interest for ongoing operations is unwise.

Cost Sharing and 5-Year Intervals Can Make It More Doable than Avoidable

In 2000 Brown & Root, recommended dredging every 5 years – a perfect match for a venture with five partners. If each budgeted one fifth of the cost annually, and you did only one fifth of the job each year, this just might be more doable than avoidable. (Avoidance seems to have been the preferred approach in the past.)

We can’t budget sediment management forever on an emergency basis. That’s like using an emergency room for basic medical care. It’s probably not the best idea, nor the most cost effective. So let’s begin the dialog with stakeholders. As Grandma used to say, “An ounce of prevention…”

Posted on July 13, 2018 by Bob Rehak

318 Days since Hurricane Harvey

USGS Report on Peak Streamflows During Harvey Significantly Revises Flood Probabilities

The U.S. Geological Survey (USGS) in cooperation with the Federal Emergency Management Agency (FEMA) released a report this week that shows inundation maps, peak streamflows, detailed flood information, and new flood probabilities from Hurricane Harvey. Hurricane Harvey, it says, was the most significant multi-day rainfall event in U.S. history, both in scope and peak rainfall amounts, since records began in the 1880s.

Flood during Harvey looking east from the south side of the West Fork of the San Jacinto. Photo courtesy of Harris County Flood Control District.

Hurricane Harvey’s widespread 8-day rainfall, which started on August 25, 2017, exceeded 60 inches in some locations. That’s about 15 inches more than average annual amounts of rainfall for eastern Texas and the Texas coast. The area affected was also much larger than previous events.

New High Water Marks and Record Streamflows

USGS field crews collected 2,123 high-water marks in 22 counties in southeast Texas and three parishes across southwest Louisiana.

Record streamflows were measured at 40 USGS streamgages in Texas that have been in operation at least 15 years. At two streamgage locations, scientists determined that the percent chance for flooding of this magnitude to happen in any given year was 0.2 percent. This probability is also referred to as a 500-year flood. Thirty other USGS streamgages experienced flooding at levels with a 1 percent chance of occurring each year, also known as a 100-year flood.

Check out the “event viewer” noted in the report, especially if you are interested in high water marks in your neighborhood.

How Data Will Be Used

The USGS conducts research on the physical and statistical characteristics of flooding, estimating the probability of flooding at locations around the United States.

The purpose of the study was to check the probability of future occurrences and map the extent of flooding in Texas.

These records will assist officials in updating building codes, planning evacuation routes, creating floodplain management ordinances, providing environmental assessments and planning other community efforts to become more flood-resilient. FEMA will also use this information to revise their Flood Insurance Rate Maps. These maps help identify areas most likely to experience flooding in any given year.

Gages Closest to Lake Houston

The section on the San Jacinto Watershed starts on page 33. The maps for the San Jacinto watershed appear on pages 35 and 36. Use the maps to see the new high water marks in the area and to find the USGS gages nearest you. For most people in the upper Lake Houston Area, it will be one of these gages:

  • 08068090 – Grand Parkway and West Fork near Porter
  • 08069500 – West Fork and I-69 near Humble/Kingwood
  • 08070500 – Caney Creek near Splendora
  • 08069000 – Cypress Creek near Westfield
  • 08068500 – Spring Creek near Spring
  • 08071000 – Peach Creek near Splendora
  • 08070200 – East Fork near New Caney
  • 08071280 – Luce Bayou above Lake Houston near Huffman

After you locate the gages nearest you, cross reference the numbers of those gages with data at the front of the report. It helps to use the search function in Adobe Acrobat because much of the information is in tables with very small type.

Examples of What You Will Find

Here’s an example of what you can find. For the gage nearest many of the sand mines on the West Fork (08068090), peak streamflow was estimated at 131,000 cubic feet per second. That was the highest of the 33 peaks previously observed at that location (from Table 3 on Page 9).

Now here’s the big news: From the same table, we can see that the Annual Exceedance Probability (AEP) is 2.4.  That’s the likelihood of occurrence of a flood of given size or larger occurring in any one year, expressed as a percentage.

AEP is often expressed as the reciprocal of ARI (Average Recurrence Interval). For instance, A 10-year flood has a 10 percent probability of occurring in any given year, a 50-year event a 2% probabaility, a 100-year event a 1% probability, and a 500-year event a .2% probability.

In this case, a 2.4% AEP would have a likely recurrence interval of 42 years, given the new realities of upstream development, any changes in climate, and pocket calculators with more computing power. This means that the West Fork Gage ((08068090) at the Grand Parkway DID NOT even experience a 100-year flood! Yes, we can expect to see worse in the future.

That’s a far cry from the 1,000-year flood that some talked about earlier and raises real public policy questions about locating sand mines in floodways.

Despite the fact that Harvey was the largest rainfall event in recorded U.S. history, USGS now predicts that it would take even bigger floods to reach the reconfigured 100-year, 200-year and 500-year recurrence intervals: 196,000, 263,000 and 374,000 cfs respectively for West Fork Gage at Grand Parkway (Gage #08068090 from Table 5, Page 14). So the new 500-year flood would have almost triple the volume of Harvey.

Humble Gage Data Missing From Report

Unfortunately, the Humble Gage at I-69 does not show up in the tables even though it is on the map and the cover of the report. This is likely in part due to the fact that the gage stopped reporting during the event due to the excessive streamflow

They may also have not reported the exceedance probability due to the shorter recent record.

For all the other gages, the Annual Exceedance Probabilities translate to new recurrence intervals ranging from 35 to 250 years. The gages at the low end of that range tend to be in the fastest developing neighborhoods.

Implications of New Findings

The report will stimulate public policy debate about development near rivers and the most effective methods of flood mitigation.

After reading this, I believe more than ever that we need more detention, dredging and gates (DDG). We need all three to help us handle the volumes of floodwater that USGS expects at more frequent intervals. Prayer, while advisable, is a less certain option in my mind than including DDG in the flood bond and passing it.

BTW, there was some confusion Tuesday night at the flood bond meeting. A small number of flood control employees incorrectly told residents that dredging would not be possible under the bond. It will be according to Matt Zeve, whom I contacted today.

Posted July 12, 2018 by Bob Rehak

317 Days since Hurricane Harvey

If You Couldn’t Attend the Harris County Flood Bond Meeting…

The Flood Bond Meeting is over. There was quite a crowd. But many people were on vacation and couldn’t attend. For those of you who could not attend, you can still submit ideas for evaluation – from the beach, from the mountains, even your grandmother’s house. All is not sunk. This is very important. It will determine whether our area gets projects in the bond proposal that will address the root causes of flooding in the San Jacinto Watershed.

The street in front of Trimble’s home as she and her son were being rescued by boat. Avoid a scene like this again by requesting that dredging, detention and flood gates be included in the Harris County Flood Bond.

What to Request

Remember, the things that will help the greatest number of people in the Lake Houston Area are:

  • More upstream detention – to decrease input
  • More dredging – to increase throughput
  • More gates for Lake Houston – for faster output

By all means, if you have additional ideas, submit those too. There is no limit.

For more information, review this post.

When you submit ideas, remember to tell the County that you live in the San Jacinto River Watershed.

How to Request

You can submit ideas up until the start of early voting. But don’t wait. Do it right now so you don’t forget. Tell the County you want more detention, dredging and gates included in the flood bond program by:

Mail:

Harris County Flood Control

ATTN: Bond Program Communications

9900 Northwest Freeway

Houston, Texas 77092

Phone:

713-684-4107

Web:

https://www.hcfcd.org/bond-program/watersheds/san-jacinto-river-bond-program/submit-feedback-san-jacinto-river-watershed/

Whew! Glad That’s Done!

You’ll sleep better if you act now, knowing that you’ve done your civic duty … and actually focused our officials on things that will make a difference for the San Jacinto Watershed.

Posted 7/11/2018 by Bob Rehak

316 Days since Hurricane Harvey

Let’s Flood the Flood-Bond Meeting Tuesday Night

The simplest, most effective thing you can do to reduce flood risk in the Humble/Kingwood/Atascocita area is come to a meeting Tuesday night, July 10 at Kingwood Park High School. From 6-8 p.m., County representatives will be there to explain the upcoming flood bond and listen to your ideas for flood mitigation. You don’t need to stay for the full two hours.

Meeting Format: Open House

The meeting format is “open house.” It will start with brief introductions from County Judge Ed Emmett, who used to live in Kingwood, our County Commissioners and Harris County Flood Control Staff. Then the action will shift to tables throughout the room where you can talk one-on-one with flood control district staff.

Drop in at any point. Get a petition from one of the RecoverLakeHouston representatives. Sign it. Hand it in. Then take your kids out for ice cream and talk about doing your duty for democracy. With cherries on top.

What We Need

The petition talks about the three things that will help this area reduce flooding the most: more upstream detention, dredging and flood gates.

  • More detention means less input during floods.
  • More dredging means greater throughput.
  • More flood gates mean faster output.

It’s the flood mitigation trifecta. Less in. More through. Faster out.

If you have other thoughts, by all means submit those, too.

Step One of a Two-Step Process

Think of this as a two-step process.

  • Step One: Make sure we get the right projects on the ballot.
  • Step Two: Vote on the projects.

Don’t worry about anything else for now. The worst thing that could happen is that the bond package passes without projects that reduce the root causes of flooding in the Lake Houston Area. You get the bill without the benefits. No one wants that.

So suspend disbelief for the moment. We can debate merits and value down the road.

After 315 Days: Your Chance to Make a Difference

This is it. The World Cup of Rivers that Runneth Over.  The Super Bowl of Flood Mitigation. The Sand Jac 500. The Tour De Lake. All rolled into one.

The Harris County Flood Bond is at hand. Let’s flood the room with attendees.

Bring your kids. Bring a neighbor. Bring a friend. Projects follow the votes. Remember: this is democracy in action. So be there or beware.

Posted on 7/10/2018 by Bob Rehak

315 Days since Hurricane Harvey