The Technology of Harris County Flood Control

story by Taelor Smith

After enduring the 2015 Memorial Day flood, the 2016 Tax Day flood, Hurricane Harvey in 2017 and other catastrophic storms in recent years, Harris County residents know all too well the unpredictability of the weather here. Sun can turn to drenching rain, and storms can linger indefinitely, bringing a year's worth of rain in a few days.

To prepare for future sudden rain events, the Harris County Flood Control District has implemented innovative technologies and systems to reduce flooding through a series of projects meant to protect communities from severe damage. The 2018 Flood Bond Program approved by Harris County voters allotted $2.5 billion for stormwater detention basins, floodplain land acquisition, improvements to the flood warning system, and other necessary updates to the county’s flood control infrastructure.

Several of the current countywide projects fall under HCFCD’s budget for Emerging Technologies and are paid for through a $25 million allocation of bond money. Four of these projects, worth an estimated $1.5 million, are under way in Precinct 4.

DRAINAGE REUSE INITIATIVE (DRI) FEASIBILITY STUDY

The ongoing Drainage Reuse Initiative (DRI) Feasibility Study will evaluate the effectiveness of using underground aquifers for rainwater storage and flood mitigation. Although the technology hasn’t been used in Harris County before, researchers are hopeful it will one day help prevent flooding across the county. "Other cities, like San Antonio and Austin, capture [stormwater] into aquifers for the use of drinking water," shares Rob Lazaro, a communications specialist for the Harris County Flood Control District. "This is one of the first initiatives to do that [in the Houston area], and the pilot study is in Tomball."

The study will determine the best of three ways to inject groundwater into Harris County's existing detention basins. The test areas within the basin will measure groundwater captured through natural drainage, enhancing drainage using dry wells, and mechanically driving water into the ground. Researchers will also consider the cost-effectiveness of each method, with natural drainage as the least expensive method and mechanically driven drainage as the most expensive. Study results are expected this summer.

RAIN GARDEN DEMONSTRATION PROJECT

Green infrastructure is another way the district fights flooding. The Rain Garden Demonstration Project is widespread throughout the county, but even more so in Precinct 4. It includes educating homeowners, homeowners associations, and municipal utility districts about the importance of incorporating green infrastructure into their landscapes to capture and slow rainwater. "These rain gardens use native plants as a natural filtration system," says Lazaro. "It slows down the water, like our detention basins would do, so that it all doesn't rush into the channel system."

Runoff from paved surfaces flows into these gardens layered with sand, topsoil, and compost to improve drainage. Not only do these gardens serve a meaningful purpose, they also create gorgeous landscapes. "It cleans the water, and it also adds a beautification aspect to many communities," Lazaro says.

HCFCD also partners with local entities to preserve natural landscapes. In Precincts 1 and 4, Houston Wilderness and HCFCD work together to plant hardy native grasses to combat invasive species as part of the Native Grass Demonstration project. Native plants are essential to prevent erosion and channel damage. When they become established, the roots of native trees, plants, and grasses hold the soil together, stabilizing the banks. Public spaces such as parks, ponds, or trails along waterways are great places to see this concept in action.

DRONES AND HIGH-DEFINITION IMAGES

For the past five years, HCFCD’s infrastructure division has used drones for data collection, including channel inspections and assessments, and to capture before-andafter photos of construction projects. Shane Hrobar, HCFCD's vegetation management coordinator, shares how this technology helps the county manage floods. "If we do a de-silt in a channel or basin, channel repairs, and things like that, we'll capture before-andafter photos from the air, in addition to what our team is doing on the ground as part of the infrastructure division’s contractor management," says Hrobar. "It's an enhancement to the work that we're already doing. As interests increase in the program’s capabilities, we will support our other divisions."

Two licensed pilots operate the drones, and a separate team works on developing the technology used by engineers across the county. Hrobar says the technology is cost-effective and helps the team update data and prepare for future maintenance projects.

"In the past, we'd have to hire someone to capture aerial imagery," he says. " Having an in-house alternative gives us another benefit and can often be quicker. It has its benefits, but it also has limitations. The two major limiting factors in drone technology today are battery endurance and line-of-sight requirements."

The team’s successful use of drones has prompted them to generate flight patterns allowing the drones to capture hundreds or even thousands of high-definition images that are later stitched together to create aerial photos. To put that into perspective, a 30-acre basin could net up to 1,200 images. These aerial photos are then used as resources for various projects, including tree and wildflower plantings. "We can return to that area over the years and take those same sets of photos to see how that site has established and grown in," Hrobar says. "This also helps to capture any repair issues."

As HCFCD continues to use this technology, there’s hope that the use of detailed imaging will include more realistic and three-dimensional images within the next two years, giving a more accurate view of waterways and floodplains.

As Harris County grows, HCFCD continues to add new ways to protect residents from floods, shaping Precinct 4's future and redefining how we use nature to our advantage. Those exploring their community should take time to admire the waterways, landscapes, and even the sky above that help protect homes and communities from disaster.