Where did all the sand come from?

Our San Jacinto River is clogged with sand that impedes the flow of water and contributes to flooding. Where did all the sand come from? When? Under what conditions? Are there ways to reduce the volume of sand coming downstream? As the U.S. Army Corps of Engineers prepares to dredge the San Jacinto for the first time, we should ask ourselves these questions.

The river has eight tributaries that affect the Lake Houston Area: Spring Creek, Cypress Creek, Lake Creek and the West Fork on the west; and Peach Creek, Caney Creek, Luce Bayou and the East Fork on the east. All produce sand naturally.

They send sand downstream at different rates at different times, depending on the location of rainfall within the watershed, the volume of flow, the speed of flow, and management of the flood gates at Lake Conroe.

San Jacinto River Watershed Map. Tributaries affecting the Humble/Kingwood area include: Cypress Creek, Spring Creek, Lake Creek, West Fork, Peach Creek, Caney Creek, East Fork, and Luce Bayou.

Other factors include the percentage of sand content in soil and the health of vegetation along stream banks. Vegetation retains and slows runoff, reducing erosion.

The Natural Resources Conservation Service of the USDA produced this soil map of Montgomery County. Blue colors indicate highest percentage of sand; red colors indicate the lowest. Note huge concentrations of sand on Spring Creek and West Fork.

The map above helps us understand why so many sand miners chose to locate along the West Fork – lots of sand. The West Fork is also sparsely populated compared to Spring Creek as you can see in the satellite image below. It shows the sand mines around the Humble/Kingwood area highlighted in red. One is located on Caney Creek (right); the rest are on the West Fork (left).

Satellite image from Google Earth with sand mines around Kingwood outlined in red. Image dated 10/28/2017.

While sand has been coming down the river and streams for thousands of years, rapid sedimentation in the West Fork between Humble and Kingwood didn’t become an issue until the growth of sand mining on the West Fork in the late 1980s.

Notice how most of the areas in red above are filled with natural vegetation in the 1985 image below.

Satellite photo of Kingwood area in 1985 before rapid growth of sand mining. Compare areas in red to previous image.

Today, mines expose approximately 20 square miles of loose sand on the West Fork alone between I-45 and US59.

Aerial photo taken on 9/14/18 of sand mining operation on West Fork.

Dikes around the mines are supposed to keep sand from being discharged into the river. However, Harvey inundated the mines.

Harvey’s floodwaters topped the dikes of sand mines. Image taken 8/30/2017.

An analysis of satellite images before, during and after Harvey shows massive loss of sand from stockpiles within many of these mines.

During floods like Harvey when the SJRA releases water from Lake Conroe, dikes are overtopped and broken. I suspect that sand then comes down the West Fork in tremendous volumes that dwarf Spring Creek’s contribution.

To test this hypothesis, I looked at USGS flow data for both tributaries. I also reviewed all my aerial photos and Google Earth’s historical images.

Under normal conditions, Spring Creek flows at 80 cubic feet per second (cfs) and the West Fork of the San Jacinto at 150 cfs. These are not sufficient flow rates to suspend sediment the size of sand. (For an excellent discussion of sedimentation, see Fundamentals of Sediment Transport at Fondriest.com.)

However, during Harvey, Sring Creek flowed at 78,200 cfs; and the West Fork at  55,000 cfs. Then the San Jacinto River Authority opened the gates at Lake Conroe. That flipped the ratio dramatically. With the flood gates open, Spring Creek still flowed at 78,200 cfs, but the West Fork increased to 130,000 cfs. Flow rates that high can (and did) move houses off their foundations.

Four hundred and fifty aerial photos in the gallery of this web site show a bright, white trail of sand between sand mines and the sand clogging the East and West Forks around Humble and Kingwood. Flood waters swept that sand from a to b. The giant sand deposits at River Grove Park and elsewhere grew exponentially during recent floods.

This tells me that when discussing the origins of the sand, we need to primarily evaluate the river during floods. More water is moving faster under greater pressure. That’s when erosion and deposition happen quickly. That’s when the river overtops and ruptures dikes. And that’s when twenty additional square miles of exposed sand surface on the West Fork make their major contribution to our sediment and flooding problems.

We can’t control sand coming down rivers naturally. However, with better sand mining practices, we may be able to reduce mankind’s contribution to our flooding problem, not to mention the related cleanup costs borne by taxpayers.

In upcoming posts, I will discuss my research into sand mining best practices.

Posted May 22, 2018 by Bob Rehak

266 Days since Hurricane Harvey

New Water-On-The-Go App Enhances Situational Awareness

The United States Geological Service (USGS) has introduced a new, real-time, web-based, all-purpose water app called “Water On the Go” that enhances situational awareness. The new GPS-aware, web app locates flood gages in 360 degrees around your current location within a user-defined radius.

Water On The Go provides real-time information throughout Texas for:

  • stream flows
  • lake levels
  • rainfall

User-Defined Alerts

Water On the Go also allows users to have alerts sent to them whenever the gages exceed user-defined parameters. For instance, if the gage at the West Fork and US59 exceeded X feet in height or Y cubic feet per second, the app would text an alert to your cell phone or email you (your choice).

How Water On the Go Works

The app automatically finds data near your current location (or any chosen location in Texas) for rapid access to water information. When you first enter the app, you are in preference pane that lets you define the type of information you are looking for. From there, you enter a map view like the one below. The app finds your location (or lets you select one. Then it automatically locates gages around you. Icons pop up representing each of the gages.

When you first enter Water on The Go, the app finds gages around you within a user-defined radius.

Special icons indicate rapidly rising streams and lakes or heavy rain that may pose a flood risk. Note the red triangles in the image above.

When you click on a gage in the radius view, detailed information from the gage pops up. You can designate it to display the type of information most important to you.

When you click on any gage, you can dig down to more information about the water at that location, including current water levels, a graph of levels in recent days, and links to more data and information.

Deceptively Deep (No Pun Intended)

The Water on the Go app is deceptively deep. It provides a wealth of historical information in graphic formats that make it easy to understand and convenient to use.

This is definitely a site that you will want to bookmark during hurricane season. In one place you can find information that used to be scattered all over the web.

I have only one suggestion. The mobile experience needs to be enhanced. Smaller screen sizes hamper functionality somewhat. The app works like a dream on desktops and laptops. It works well on tablets. But on cell phones, it can be a bit of a struggle to pinpoint locations with fat fingers. Of course, I had GPS tracking on my phone turned off for privacy reasons. I’m sure it works much better with GPS tracking turned on.

For Flood Warnings, Fishermen and More

I expect that most members of the public would find this app especially valuable in several situations.

  • When approaching storms dump massive rainfalls upstream, you could see floods coming downstream at you and monitor the closest gages to determine whether and when you should evacuate..
  • When boating, you can set lake an stream level alerts to warn you when water levels drop below minimums.
  • When traveling vacationing, as I was during Harvey, you could use the app to navigate around trouble spots and check whether your home is in danger.
  • When you have friends, relatives or children whom you are concerned about in another location, you can check their safety at a glance.

The app even lets you monitor water temp, oxygen levels and turbidity – factors that fishermen could find valuable.

This application was developed by the U.S. Geological Survey Texas Water Science Center Data and Spatial Studies group and is fueled by USGS Water Services.

My thanks to Diane Cooper for alerting me to this new tool. Diane is a FEMA employee who has more than 20 years of experience forecasting floods and weather for the National Weather Service.

A Testimonial

As I was composing this post on Sunday evening, I received a text alert from Jeff Lindner of Harris County Flood Control. He warned that parts of Spring and Little Cypress Creeks might be coming out of their banks. I checked them with the app about an hour later. Sure enough, the gages for those creeks indicated trouble exactly where he indicated.

Check out Water on the Go. Better yet, bookmark it and sign up for alerts.

https://txpub.usgs.gov/water-onthego/

Posted May 21, 2018 by Bob Rehak

265 Days since Hurricane Harvey

A Personal Flood-Control Wish List For the Lake Houston Area

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.

San Jacinto River Watershed Flow Rates

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