Halls Bayou Illustrates Cost, Difficulty of Flood Mitigation in Overdeveloped Areas

Flooding within the Halls Bayou watershed illustrates what happens when development, density, lack of detention and insufficient distance from streams put people and their property in harms way. Instead of protecting a strip of green space near the bayou years ago, developers built right up to the edge. As density increased and developers built further upstream without sufficient detention, people who crowded the Bayou then started to flood repeatedly.

As the images below show, once developed, the cost and time of mitigation increases exponentially.

All of that argues for better planning and the protection of green spaces that can accommodate future floods and flood mitigation projects throughout the region.

Halls Bayou Not Unique

This same scenario happened repeatedly in other Houston watersheds: Greens Bayou; Braes Bayou, White Oak Bayou, and Cypress Bayou, for instance. But let’s save those for future posts. For now, let’s go back.

Solution Well Known for More than a Century

In 1913, recognizing the potential for continued growth, a well-known landscape architect, Arthur Comey created the first comprehensive plan for the Houston Park Commission. He observed that Houston ranked far behind other major U.S. cities in parkland. It had one acre of park for every 685 residents. Seattle was a distant second at 224 residents per acre.

To address this inequity, Comey’s plan included a visionary idea. Noting that the city’s network of bayous were already “natural parks,” he proposed a series of linear and large parks along their lengths.

As he wrote, the “bayous and creek valleys readily lend themselves to trails and parks and cannot so advantageously be used for any other purpose.”…

Unfortunately, developers ignored him.

About Halls Bayou

The Halls Bayou Watershed encompasses a city within a city.

• Older homes and businesses are densely packed.
• Many are built right up to the edge of the Bayou.
• 70% of the population is low-to-moderate income.
• You see far more signs in Spanish than English

Economically, the area looks poor. Culturally, it feels rich.

Frankly, as I drove through it last weekend to photograph flood mitigation projects, it felt much more vibrant than more affluent neighborhoods father to the north or south.

For the most part, people have fixed their homes since the last big flood. These folks may be poor, but the vast majority take great pride in what they have.

The map below shows the route of Halls Bayou through surrounding mid-north neighborhoods. Homes are packed so close to the bayou that it’s hard to see it in places, so I outlined the route in red.

Now, let’s superimpose floodplains over the same area.

North to south along US 59 (on right), the floodplain extends almost 3 miles. And it will extend even farther when new maps based on Atlas 14 are officially released based on Harvey data.

Below, see how that area looks today where Halls Bayou crosses under US 59. Note the large detention ponds where the subdivisions used to be.

Each took about three years to build.

Time, Costs of Buyouts

Before HCFCD could construct the detention ponds, it had to buy out homes in adjacent subdivisions and demolish them. Buyouts in this area began in 2002 when HCFCD received a large grant from the federal government after Allison. That took at least another three years.

Then Flood Control had to get permits from the City of Houston to demolish the streets. That took years.

So from 2002 until completion of construction took 13 to 16 years (2015 and 2018). But the construction itself took only 3 years.

Thus, the total project took 4-5X longer than construction.

$1 of Prevention Worth a $1000 of Cure

This area started to develop in the 1940s. The earliest image in Google Earth (1944) shows that it was the edge of the City then. With more wetlands and farm land to absorb rainfall, the flooding problems were probably not as bad. A few scattered subdivisions pressed against the edges of the bayou. But the lots were large.

Compare again the shot above with the one below for a dramatic example of infill development. It’s nothing like today.

Just looking at these two maps, you can see how the dramatic increase in density limits flood mitigation possibilities and raises costs. We no longer have any easy solutions.

To make matters worse, despite flooding, people often fight buyouts. They fear leaving neighborhoods, friends, family and support networks.

Should Have Known Better

People knew or should have known the area was flood prone. But they built or bought there at great risk to themselves, and ultimately at great cost to the community.

That raises the question: Why were people allowed to build so close to the bayou in the first place? Why wasn’t sufficient green space left along the bayou to widen it or build detention ponds?

There are no simple answers to that question. Residents may not have felt at risk until upstream development sent more water downstream faster. They may not have been knowledgeable enough about flooding to ask the right questions.

Some just wanted to live close to work. Some wanted to be near family and friends. Some needed neighborhood support groups. And some just pushed their luck because they liked the view or location and the lots were cheap. Now, we’re all paying the price.

Posted by Bob Rehak on April XX, 2021

13XX Days since Hurricane Harvey

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