Tag Archive for: proximity

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 harm’s 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; Brays Bayou, White Oak Bayou, and Cypress Creek, for instance. But let’s save those for future posts. For now, let’s go back in time.

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 comprises 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.

Route of Halls Bayou through mid-north part of Houston. Airline Drive is on left, I-45 in middle and US 59 on right.

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

Floodway = cross hatch, 100-year floodplain = aqua, and 500-year floodplain =tan. Map last updated in 2007 based on data from Tropical Storm Allison.

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. The image below shows what the area around US 59 and Halls looked like in 2002 shortly after Tropical Storm Allison.

Note subdivisions built right next to bayou.

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

Note the two large detention ponds, one on either side of the freeway. The one on the left was substantially completed in 2015 and the one on the right in 2018.

Each detention basin 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 near the detention areas above began in 2002 when HCFCD received a large grant from the federal government after Allison. Google Earth images show that the buyouts took at least another three years.

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

So from 2002 until the 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 Flood Mitigation

This area started to develop in the 1940s. The earliest image in Google Earth (1944) shows that it was at 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. And had green space been set aside then, the story today might be different.

Halls Bayou in 1944. Note: only two subdivisions started to encroach on the bayou. Rest was rural.

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

Compare the dramatic increase in density with the decrease in bayou width.

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. Most people in neighborhoods like this depend on support networks of friends and family. They fear leaving those networks. Many date back generations.

Should Have Known Better

Developers and home buyers knew or should have known this area was flood prone. But still, they built or bought here 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 the support. And some just pushed their luck because they liked the view or location and the lots were cheap. Regardless, everyone is paying the price for decisions often made decades ago.

Posted by Bob Rehak on April 28, 2021

1338 Days since Hurricane Harvey