Commons on Lake Houston Archives

3/25/25 – Almost eight years after Hurricane Harvey and a massive region-wide effort to update flood maps, FEMA still features maps on its website based on decades-old data that don’t come close to showing true flood risk. The old maps cause confusion among homebuyers who may not understand their limitations. And that helps developers pursue and profit from risky ventures in floodplains.

Three-Year Delay for New Maps and Still Counting

FEMA has yet to release maps based on recent Atlas-14 data developed after Hurricane Harvey. Harris County Flood Control District (HCFCD) anticipated release of FEMA’s new preliminary maps three years ago and release of the final maps by now. See the timeline below published in 2020.

*Source: Screen Capture from Harris County Flood Control District* *MAAPnext site in 2020.*

I requested the release date for the new maps from Harris County and Federal officials. However, they did not respond.

Delays Contribute to Confusion about Safety of New Developments

The delays have contributed to confusion about the safety of new developments near or in floodplains.

Take, for instance, the lawsuit between the City of Houston and one of the area’s largest developers. According to a Texas Supreme Court decision released last Friday, the Signorelli Companies want to develop more than 500 lots near the San Jacinto East Fork as part of The Commons of Lake Houston.

Plats show most of the lots outside the current 100-year floodplain. But floodplains will reportedly expand by 50-100% when the new flood maps come out. At that point, most if not all the lots will likely be deep in the floodplain.

So, the City imposed higher elevation requirements for homes in anticipation of the new flood maps. That triggered a property-rights lawsuit by the developer, which claimed the City’s requirements made the property “undevelopable.”

Sometimes We Just Never Learn

Sometimes, it feels as if we just never learn. I understand a company’s desire to make money from its land. But unsuspecting homebuyers could lose their life savings. Worse, more people could die.

Flood insurance is becoming unaffordable for many. Insurance companies are fleeing high-risk areas.

And we haven’t even mentioned yet the costs of flood mitigation, disaster relief, buyouts, and restoration of the natural ecosystems – that already protect people for free.

In my opinion, for the public good, some land just shouldn’t be built on.

The Commons of Lake Houston Proposal

The flood map for the Commons area on the East Fork was last updated in 2007. It is based on data acquired after Tropical Storm Allison in 2001. New Atlas 14 rainfall data is 30-40% higher than previous estimates and represents the current best efforts of scientists.

The map below shows the extent of those 100- and 500-year floodplains in 2007 maps as dotted lines superimposed over a proposed new section of the Commons called the Crossing.

*Close up of plat. *Floodway is to left of heavy dotted line. 1*00-year and 500-year floodplains are shown as lighter dotted lines farther right.*

Two Pictures Worth 2,000 Woods

These two pictures, sent to me by a nearby resident of an existing home on higher ground in the Commons, illustrate the problem.

*First image shows extent of the Harvey flood. Second shows Signorelli’s proposed development. High water mark during Harvey identified as Position 1.*

Think such a flood can’t happen again in your lifetime? That Harvey was a thousand-year storm?

It almost happened again in May 2024 during a no-name storm a month before the start of hurricane season. The screen capture below shows historical HCFCD data from a gage just upstream from the Commons. Note the last three entries.

*Historical flood heights from Harris County Flood Warning System Gage at East Fork and SH99.*

That no-name storm produced flooding almost five feet higher than Imelda and only about four feet lower than Harvey. It was the second highest flood at that location since HCFCD started keeping records!

Will We Repeat Mistakes of the Past?

The thing about floodplains is that they keep growing with upstream development – especially as other developers push into wetlands near rivers and streams. And the area upstream from the Commons is growing very quickly.

At some point (like now), it may make more sense to donate this land to an organization such as the Bayou Land Conservancy, Houston Parks, or Texas Parks and Wildlife. That would offer the developer some tax benefits. That could also help protect the public, protect lenders, help hold down insurance rates, provide recreation, and reduce future mitigation costs. It would even likely add value to homes on higher ground.

Posted by Bob Rehak based on 3/25/25

2765 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.

A resident of The Commons on Lake Houston contacted me about some severe erosion in her community. I can only describe it as stunning. It destroyed trails owned by the Property Owners Association that people used for hiking, biking and horseback riding. The loss of these trails limits recreational opportunities and has physically divided large parts of the community.

Sadly, it didn’t have to be that way. Infrastructure and ditch maintenance did not keep pace with development.

As development crept closer to the East Fork of the San Jacinto over the years, the erosion worsened. In older neighborhoods on higher ground, a series of small check dams in a major drainage canal reduced erosion.

A check dam is a small dam constructed across a drainage ditch to counteract erosion by reducing water flow velocity.

*Wide grassy, gentle slopes and check dams keep erosion at bay in areas first developed.*

*The last check dam. Downstream, it’s different.*

Below Check Dams, Uncontrolled Erosion

The dams stop short of the East Fork. A tiny swale that residents used to step over has expanded into a steep-sided gully approximately 20 feet deep and 50-75 feet wide. Not even concrete can stop the erosion now.

*Concentrated runoff below the check dams has peeled away concrete used to reduce erosion around this pipe.*

Trails used to run alongside and across this ditch. Now they’ve been swallowed. Residents have nicknamed the ditch “The Grand Canyon.” They fear walking near the edge because of potential for cave-ins.

*Water exits the other side of the pipe with the force of a fire hose. It has eroded a huge bowl, now eating trails and trees.*

*Further downstream, a shallow ditch has turned into what residents now call “The Grand Canyon.”*

*Resident points to where part of a horseback riding trail caved in.*

*Trees falling into the center force the water wider during floods, worsening erosion.*

*This tree created an eddy that ate away a foot path. It went from lower left to upper right.*

Causes of Erosion

Erosion can result from many things. Multiple factors played a role in the Commons.

As the developer built up land to elevate foundations, he increased the slope. That accelerated runoff.

Clearing land for a new subdivision along the ditch also accelerated erosion of soft, sandy soil.

Finally, concentration of runoff also played a major role. When runoff spreads out over over acres, it poses no threat. But concentrating it turns a thousand trickles into a firehose aimed at loose, sandy soil. The result: severe erosion every time it floods.

Residents of The Commons have already seen how that erosion can destroy recreational opportunities and infrastructure. They pray that their developer will fix the Grand Canyon before it starts eating homes.

Lessons for Kingwood

This Commons story contains timely lessons for the residents of Kingwood as we consider a potential high-rise development in the floodway and floodplain of the San Jacinto.

The Commons erosion reminded me of the Kingwood Rapids. Whitewater enthusiasts gave that name to the drainage ditch that runs between Kingwood and Forest Cove near Deer Ridge Park, just south of Walnut Lane (see below).

The drainage ditch between Walnut Lane and Deer Ridge Park has jokingly been dubbed the Kingwood Rapids by whitewater enthusiasts. Ditch erosion now threatens yards and fences. Image courtesy of Google Earth.

The proposed new high-rise development would use this ditch to drain hundreds of acres that they intend to pave with concrete.

*“Kingwood Rapids” in 2009 shows same processes at work here that threaten the Commons.*

High-Rise Concern: Erosion and Incision

As you can clearly see, the ditch can barely handle existing runoff during storms. It’s severely eroding.

Draining high-rise, high-density commercial space into these ditches will cause them to “incise.” Incise means “cut into.” Runoff will deepen and/or widen ditches. But ditch erosion already threatens nearby homes.

This same ditch runs through River Grove Park, which already cost Kingwood residents more than half a million dollars in repairs after major storms in 2015, 2016 and 2017. The soccer program at River Grove still has not fully recovered. The lacrosse league has abandoned its lease there. One shudders to think of the damage that the loss of River Grove to do to the entire community.

Impact on Water Quality

All this erosion also has a direct impact on water quality in several ways. First, the sediment flows into the lake. There, it reduces lake capacity. The sediment also increases turbidity, which increases water treatment costs and harms riparian vegetation. That vegetation helps stabilize banks, protect property and provide cover for fish which waterfowl and eagles feed on6

More food for thought as you compose your letters to the TCEQ and Army Corps.

Posted by Bob Rehak on 1/16/2019

506 Days since Hurricane Harvey

Tag Archive for: Commons on Lake Houston

What Happens When Flood Maps Don’t Illustrate True Risk