Tag Archive for: Mavera

West Fork Sludge Fest

The San Jacinto West Fork has turned into a sludge fest again. I took the picture below on 11/11/23. Not since the day that the West Fork turned white have I seen the contrast so dramatic at the confluence with Spring Creek.

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Looking NW from over US59 Bridge. Confluence of Spring Creek (left) and San Jacinto West Fork (right). Cypress Creek joins Spring Creek 2.7 miles west of this location.

In that prior case, the cause was obvious. Two sand mines were discharging process wastewater into the West Fork. The TCEQ determined that one, the Liberty Materials mine, dumped 56 million gallons of white sludge into the river.

This time, the cause is not so obvious. I can’t even be certain I determined the cause. After taking the photo above, I spent a whole day ruling out various possibilities while searching for others.

Ruling Out Causes

The dramatic difference was not caused by huge variation in rainfall totals across the region.

Rainfall totals from Harris County flood warning system. All of the rain fell in the previous 2.5 days and was relatively spread out.

The highest total on the West Fork was that 2.68 inches south of Conroe at SH242. Further investigation showed that 1 inch fell between 3 and 4PM on 11/09/23. That was the highest intensity at that gage in more than a month.

Uneven soil saturation across the region would also not cause the zebra pattern in the river. The entire region is still rated either “abnormally dry” or in “moderate drought.”

And Lake Conroe did not release any large volumes of water lately that would have scoured river banks. That eliminated another potential cause.

Now here’s where it gets really baffling.

SJRA Study Claims Most Sediment Comes from Spring/Cypress Creeks

The San Jacinto River Basin Master Drainage Study by Freese & Nichols claims that more sediment comes down Spring and Cypress Creeks than the West Fork.

In fact, they say, of all the sediment coming into Lake Houston, two thirds comes from Spring and Cypress Creeks while only 13% comes from the West Fork upstream of US59. So where is all the sludge coming from?

In my opinion, it most likely came from new developments or sand mines that move large volumes of loose sediment.

So the next day, I went out with my drone and found several possibilities.

Possible Sources for Sediment Pollution

Two sand mines had pits open to the river, but I did not see large volumes of sediment oozing out of them as I sometimes do.

The most interesting possibility: new developments very near that gage on SH242 that read 2.68 inches.

Two connected developments straddle FM1314 immediately north of SH242. Early plans called them both Mavera. But now, the one on the east has a sign that says Madera. The sign on the west section calls it Evergreen.

Both are being built on top of wetlands in a 10-year flood zone. Together, they have roughly 1400 acres of exposed soil.

Most of the development’s stormwater drains into Crystal Creek and then into the West Fork about a half mile downstream from where I took this photo.

Sediment-laden stormwater burst through the wall of this detention basin.
Enlarged detail from shot above shows water was strong enough to destroy the outfall pipe.

Now let’s see what’s upstream from this breach.

Evergreen drainage channel. Water flows toward camera and the breached detention basin.
Even farther up the channel. Note all recently exposed sediment.

The ditch above appears to be much wider than it was in January 2021, almost three years ago. Now, let’s jump back south to where this area drains into the West Fork.

Crystal Creek (middle) empties into the West Fork (bottom left). Note how milky water from Crystal compares to the West Fork.

Note that the picture above was taken two days after the heaviest recent rainfall, so the volume may not seem impressive.

There likely were other areas along the West Fork that contributed to the sedimentation you saw in the first photo at the top of this post. But I was not in a helicopter and it’s virtually impossible to cover the entire river with a drone. So I can’t say for sure.

How to Report Issues You May See

This is not the first time I have documented excessive sediment coming off the West Fork.

The zebra effect at the confluence is common.

The angle of the shots above varies. But in each instance, the West Fork is the most polluted branch.

Why is sediment so concerning? After all, it’s natural, right?

Remember the mouth bar that virtually blocked off the West Fork after Harvey? Also the one on the East Fork?

When sediment reduces the conveyance of rivers, they come out of their banks faster and higher on smaller rainfalls. The rivers flood more frequently and increase your flood risk.

So, if you see unnatural situations in rivers or streams, make sure you report them to the TCEQ, which investigates such matters.

Together, we may be able to improve our safety and water quality.

Posted by Bob Rehak on 11/13/2023

2267 Days since Hurricane Harvey

The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.

Mavera Clearing More Land West of FM1314

The Pulte Homes Mavera development at FM 1314 and SH 242 comprises approximately 2000 acres. Contractors first focused on clearing the 865 acres east of FM 1314. Photos taken on 7/22/2022 show they’re now also focusing on the 1150 acres west of FM 1314. Significant clearing in this western portion has already occurred. But more remains.

Map of Mavera At Ultimate Buildout

Map excerpted from developer’s 5/29/2020 memo to Montgomery County engineers.

Photos From West to East

Looking west from middle of western portion of Mavera. SH 242 in background. Channel drains into Crystal Creek which drains into West Fork San Jacinto by sand mine ponds in upper left.
Looking south from same position. SH 242 cuts left to right through upper middle of frame. Ponds in background are sand mines bordering the San Jacinto West Fork.
Looking east from same position at drainage coming from eastern portion of same development in distant background.
Moving farther east toward FM 1314. Still looking east. SH 242 cuts diagonally from middle right toward upper left.
Intersection of FM 1314 (bottom) and SH 242 (right). Looking east toward first section cleared and drained.
Eastern-most section of Mavera. Looking NE.

Hydrologic Timing Used to Reduce Detention Requirements

While Mavera will provide some linear detention in the main channel along with some small ponds, it relies heavily on a hydrologic timing study to avoid building all the floodwater detention capacity normally associated with a development of this size.

Hydrologic timing studies attempt to show that a development can get stormwater to a river, such as the West Fork, before the peak of a flood arrives. The theory: if you aren’t adding to the peak, you don’t need as much detention.

However, Harris County discourages the use of hydrologic timing. It encourages developers to get their water to the river as fast as possible. If enough developments do that, it can shift the peak. Regardless, Montgomery County still allows it.

In a hundred-year (1% annual chance) flood, this development claims it will not add to the peak. And therefore, it will have no adverse impact downstream. Yet it alone sends more than 16,300 cubic feet per second downstream toward West Fork sand mines and the Humble/Kingwood Area. That represents about 10% of the water that came down the West Fork during Harvey at this location.

Posted by Bob Rehak on 8/2/2022

1799 Days since Hurricane Harvey

The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.

Mavera Wetlands Bite the Dust

Mavera, a 1700-acre new development in southern Montgomery County at FM1314 and US242 has finished clearing a large section of land northwest of the intersection and started pouring concrete. Signs welcome visitors to model homes. The area, once laced with wetlands now has a massive linear detention pond and uses FM1314 for outflow control.

Looking east just north of US242 on right from over FM1314. Note wet areas in foreground. They correspond to wetlands in map below.
Large green area immediately east of 1314 (diagonal) and north of US242 (bottom) correspond to wet areas in photo above. From US Fish and Wildlife Service National Wetlands Inventory Map

Areas west of FM1314 to Crystal Creek are also being cleared, but their current state of development is not quite as advanced.

Looking west from over FM1314 at area being cleared. This area has not changed much since January when I last posted about the development.

Likewise, an area east of FM1314 has expanded north, almost to Gulf Coast Road. Neither is its drainage fully developed.

Looking NE at current limit of development. Gulf Coast Road runs diagonally from left to right just beyond tree line.

Long, Linear Detention

The development relies on a wide linear detention basin – more than a mile long! And that’s only the part east of FM1314!

Looking east toward upstream end of detention basin.

Two smaller basins also exist. One is currently by a small park and recreation center.

Looking WSW. Note small retention pond and rec center in upper right.

In the photo above, also note the small swales that outline lots. Will some drainage go overland? Or is underground drainage just not connected to the detention basin yet?

Same spot. Lower elevation. Looking west from eastern portion of Mavera. I’m not seeing any drainpipes from storm sewers entering pond yet.
Note three new model homes near center of frame.

The Mavera website by Centex homes says the swimming pool at the rec center will open late this summer. Pulte will also build homes in Mavera.

Name Changes and a “Beat the Peak” Drainage Analysis

I previously posted about Mavera in January. Compare the pictures taken then.

The development seems to have undergone a series of name changes. The land was originally known as the Denbury Tract. Later, construction plans and a drainage analysis refer to it as Madera. But now, the builders are marketing it as Mavera.

Screen capture of cover sheet from drainage plan showing first two names of development.

The drainage plans for Mavera (aka Madera/Denbury tract) rely on a hydrologic timing assessment (see last line in screen capture above).

Harris County has tried to discourage neighboring counties from using such analyses. They encourage developers to get stormwater to streams and rivers faster rather than slower. The theory is that if you can beat the peak of a flood then you aren’t adding to it. But if everybody tries to “beat the peak,” eventually you shift the peak and flood downstream neighbors. For a full discussion of drainage issues, see my previous post.

The drainage analysis claims the development will have no downstream impact, but engineers didn’t study those areas. Nor did they study how new development upstream may have already shifted the peak of a flood.

Impact on FM1314?

Long linear detention schemes typically accelerate the flow of water. This one will rely on one culvert under FM1314 to hold back more than a mile of water collected from hundreds of acres. That will put a lot of pressure on FM1314 in a heavy storm.

Looking NW over FM1314. East is to the right. Water will flow west toward Crystal Creek out of frame to the left.

The roadway will act as a dam to detain water collected from almost all of the area shown in the photo below.

Looking east. Virtually all of the cleared area will drain through one culvert under FM1314. FM1314 runs left to right through the bottom of the frame. US242 is on right. Notice how channel is being widened, making culvert off-center. Did someone initially miscalculate or did plans change?

Let’s hope all that water doesn’t blow out the road like Colony Ridge drainage blew out FM1010 in Liberty County.

For Potential Home Buyers

FEMA mapped most of this area in a ten-year flood zone. For the sake of potential home buyers, let’s also hope the engineers got the drainage calculations right.

Potential homebuyers may also be interested in reading about the risks of building homes over wetlands.

Posted by Bob Rehak on 7/16/2022

1782 Days since Hurricane Harvey

The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.