On August 25th, the anniversary of Hurricane Harvey, Harris County residents will vote on a $2.5 billion flood bond. The County has not yet made clear what mitigation measures would be in the bond proposal. Hence, my personal wish list. Not all items on the list below are suitable for a bond, but could still help mitigate flooding. I’m including them here to have them all in one place. You may have other ideas. Let’s start a public dialog. Please contact me through this website or on Facebook with your opinions. I will collect and publish all credible ideas on behalf of the community.
Causes of Flooding in the Upper Lake Houston Area
Before we start, it’s important to note that the main type of flooding in our area is riverine. Humble, Kingwood, Atascocita and Huffman sit at the confluence of two main forks of the San Jacinto River.
Together, the East and West Forks drain more than a thousand square miles upstream through smaller tributaries. Those include Spring Creak, Cypress Creek and Lake Creek on the West Fork; and Caney Creek, Peach Creek and Luce Bayou on the East Fork.
Hurricane Harvey brought an estimated 400,000 cubic feet of water per second (cfs) down those tributaries to Lake Houston. The release from the dam at Lake Conroe at the peak of the storm was 79,141 cfs.
Where Water Came From During Harvey
That 79,141 cfs was approximately one third of 236,000 cfs coming down the heavily populated area between Kingwood, Humble and Atascocita where most of the damage occurred at the peak of the storm.
Both the West Fork and East Forks contain massive sand mines that were inundated by Harvey. As the photos elsewhere on this website show, those floodwaters swept up sand, carried it downstream, and deposited it at choke points that now create higher-than-expected floods on lower-than-normal rainfalls.
My Personal Flood-Remediation Wish List
1) Add upstream retention to reduce the amount of water coming downstream at peaks. Such retention would have to be built in unpopulated areas. That limits possibilities, however, it does not eliminate them. Lake Creek, Peach Creek and/or the East Fork of the San Jacinto all contain natural areas that could be considered as candidates. Ideally, the amount of extra detention would at least be sufficient to offset releases from the dam at Lake Conroe.
2) Regularly dredge the East Fork, West Fork, and drainage ditches. The frequency should be at least every 5 years, the interval recommended in 2000 by the Brown & Root Regional Flood Protection Study (page E-9). Sand mines continue to send huge volumes of sand downstream with every flood. The sand blocks drainage ditches and restricts the cross section of the river. That creates higher-than-expected flooding on relatively small rains. Regular dredging does not necessarily have to occur at public cost. Tax incentives could encourage sand mining companies to dredge the river at their own expense. They could sell the recovered material to help recoup costs. However, this would have to be done under government supervision to discourage excessive dredging that undermines river banks.
3) Add more flood gates to Lake Houston. This would allow the City to release water earlier and faster during major storms. This could create extra capacity in the lake to absorb flood water. Lake Houston has two small floodgates, but they have one tenth the capacity of the gates at Lake Conroe. In combination with the sand deposits mentioned above, this can create a bottleneck. (Note: the Harris County bond could not help with flood gates because the gates would be City of Houston assets. The City is currently securing funding for this project through the Texas Department of Emergency Management, FEMA and the Federal Government.)
4) Improve coordination/communication between the people who control dams at Lake Conroe and Lake Houston, and the public. This could improve public safety two ways. First, when the discharge capabilities of both lakes are balanced, they could release water in advance of major storms as a flood mitigation strategy. (Currently, SJRA fears that releasing water before storms could overload the downstream watershed and cause the very flooding that a pre-release strategy is designed to prevent. This is a complex issue.) Second, during Harvey, actual release rates seemed to lag public announcements, creating a false sense of security among residents downstream. Better communication could have given residents downstream time to evacuate in an orderly fashion and save their most valuable belongings.
5) Link real-time inundation mapping (currently being developed) to expected Lake Conroe release rates. Harris County is already working on a real-time inundation mapping system. This system will model flooding down to the block level. It would enable people to see how fast flood waters were rising in their neighborhoods, help them determine when to evacuate, and identify safe escape routes. Now imagine making this system available to the engineers who control the Lake Conroe dam. ALSO imagine adding features that enable them to preview and test the impact of different release strategies. For instance, “How many homes downstream will be flooded at different release rates? Which strategy would flood the fewest homes? How much water can we safely release without flooding any homes? If we have to flood homes, who should we warn? How much time will they have to evacuate?”
6) Add sensors and gages throughout the watershed to create a more detailed picture of what is headed inbound toward Lake Conroe and Lake Houston during severe events. Such sensors and gages would support the preview capabilities outlined in point #5 above.
7) Improve sand mine operations to reduce the amount of sand coming downstream. I would like to see a government/industry/public panel created (with public hearings) to review sand mine operations and suggest improvements. The objective would be to identify affordable best practices that could reduce sand losses, minimize dredging costs, and help protect the public. This could also reduce turbidity which would improve fishing and recreation while reducing water treatment costs. I can think of four potential strategies off the top of my head: a) replanting areas no longer actively being mined to reduce erosion, b) building walls around stockpiles that protect them from floods, c) strengthening dikes so they don’t collapse, and d) giving the river more room to expand during floods. In regard to the latter, the dikes are currently built right at the river’s edge, leaving no room for the river to expand before it floods the mines.
Sand mines by Sorters Road in Montgomery County west of Kingwood. Note how the placement of their dikes give the West Fork no room to expand during a flood. This contributes to dike collapse, mine inundation and loss of sand.
8) Temporarily lower the level of Lake Conroe. Lower the level up to one foot during the rainiest months in spring and up to two feet during the peak of hurricane season. While two feet may sound draconian to some Lake Conroe residents, on average, it’s really only 4.8 inches below the amount usually lost though evaporation during September. This is the only buffer that the upper Lake Houston area can have against flooding until we implement other mitigation measures. The SJRA board has already approved this proposal, but the City of Houston and the Texas Council on Environmental Quality have not yet done so. The Lake Conroe Association has vowed to fight a two-foot lowering.
9) Create more public green spaces near the river. I would like to see groups such as the Bayou Land Conservancy work with cities, counties and the state to buy up undeveloped and abandoned land along the river. They could then put conservation easements on it to help protect us all from future flooding. Keeping that land natural would reduce runoff; provide a buffer between homes and harm; preserve nature and wildlife; improve water quality; and create more recreational opportunities.
10) Improve communication during power outages. We need a way to warn people when power is knocked out during a storm, cell towers are overloaded, and people are sleeping. Simply publishing information is not enough if people cannot receive it. Perhaps we need sirens linked to back up generators, like those used to warn people of tornadoes throughout most of the midwest.
What are Your Ideas?
Please use the contact page on this web site to send me your ideas. I will add them to this list and present it to city, county, state, and river authority officials. This area probably has more geoscientists and engineers per square foot than anywhere in the world. Please help. Sound off. Let your voice be heard. Let’s show the world we can lick this problem together. If you wish, I will protect your privacy by publishing your thoughts anonymously.
Posted April 20, 2018, by Bob Rehak
Day 264 since Hurricane Harvey
