Houston plans to restore bayou forests to combat urban heat

Welcome to Heat Week. From July 1-5, Chron examines how heat has defined our lives in Houston and Texas: the good, the bad, and the grueling.

If you’ve ever been out for a walk on a hot summer day and happened to step under the shade of a beautiful, large tree, even if only briefly, then you know the difference shade can make in beating the Houston heat.

But in Houston, shade is scarce. An analysis by the Kinder Institute for Urban Research found that Harris County lost about 10 percent of its tree cover between 2011 and 2021. And that’s not all, thanks to climate change, the Earth is warming. Last year, the National Oceanographic and Atmospheric Administration recorded the hottest summer on record (in its 174-year history) at 3.4 degrees Fahrenheit (1.2 degrees Celsius) above average. And as we’ve all seen, this summer already looks set to be scorching hot (with a healthy dose of humidity).

As Texas summer continues to bring increasingly unavoidable heat, the urgency to reduce urban heat grows.

But the city of Houston has a plan to get there, starting with restoring natural forests near its waterways. According to the Texas General Land Office’s Resilience Master Plan, Houston aims to plant 200,000 trees along narrow strips of land adjacent to bayous as part of the Houston Parks and Recreation Department’s Riparian Restoration Initiative. Since YEARTK, the city has planted 35,000.

Riparian areas, or areas between land and a river, stream or bayou, act as buffers between upland areas and open water. Many of Houston’s riparian forests have been damaged, cleared or overgrown with non-native species, which not only hinders flood mitigation but also heat reduction efforts.

“These trees generally improve the heat in Houston, not just when an individual is standing under a tree,” said Kelli Ondracek, natural resources manager for the Parks Department. “Trees cool adjacent areas, so these trees help cool Houston.”

Trees absorb the sun’s rays in the summer, causing the areas directly beneath the tree to receive only 10 to 30 percent of the sun’s heat. Additionally, more trees help cool the area by transpiring water through their leaves, which has a cooling effect, and combined with the shade, can lower temperatures by 2 to 9 degrees Fahrenheit, according to a report from Grist.

The Parks Department has identified 70 parks and waterways in southeast Houston that need restoration. So far, 26 sites have been restored, according to TreePlotter.

But why not reach the target of 200,000? Well, it is always due to the lack of means and personnel.

The program has been in the works for years. Its first pilot projects began in 2017 when the department received funding to restore Milby Park and White Oak Parkway, Ondracek told the Chron.

After that, they were able to get funding from the Texas Environmental Quality Commission and the General Land Office to start new projects. However, according to the Resiliency Master Plan, the initiative as a whole was not fully funded, only some individual projects. The total cost of the project is estimated at $4 million.

And as the department takes on new projects, there aren’t enough staff to go back and maintain sites. The department has to be vigilant the first year after a site is restored, but after a few years, older sites are only maintained once a year. But as the department adds sites, it’s hard to keep tabs on many of the younger sites.

“As we add sites and get closer to 70 sites, we’re always going back to the sites that we’ve restored,” Ondracek said. “We’re adding additional (planting) sites every year without really adding additional staff… The biggest challenge is just making sure that all of these sites continue to function well and don’t get taken over by vines and invasive species.”

Riparian restoration projects include planting native trees including river birch, pecans, southern magnolias, American holly, sweet gum, American sycamore, taeda pine, cottonwood, black cherry, white oak, southern red oak and more. The Park Service is adding interpretive signage to all of its projects to identify and inform residents of native plant species.

The Houston Parks Department recently worked on a rare riparian restoration at Watonga Park, creating a “wooded bumper” on both sides of the bayou. Ondracek said the department will begin work at Hermann Brown Park next year to enhance its existing riparian forest.

As they continue to work on more sites, Ondracek believes they will reach the goal of 200,000 trees.

“I think we will reach at least that amount for the project,” Ondracek said.