Case Study: Using Plants to Stabilize UT’s Hills

ADA ramp near stadium with erosion control

 

Just two years ago, every storm swept inches of mud onto ramps and sidewalks where the natural topography of campus—namely, an increase in elevation of about 100 feet on both sides of Waller Creek—was not in sync with the footprint of buildings. But a recent addition of plants, gravel, and straw is stabilizing hillsides in several areas of campus.

“Water wants to follow its original path and end up in the creek,” says Lisa Lennon, UT Austin’s Landscape Architect. “There are usually two solutions to mitigate erosion: constructing new infrastructure, which can be expensive and time-consuming, or adding selective plant material to slow the flow of water naturally.”

Lennon and the installation team in Landscape Services have recently completed several projects that demonstrate how simple alterations to hills can both reduce erosion and beautify campus. Both case studies are from the steep terrain rising east of Waller Creek, as anyone looking at E. 23rd Street between San Jacinto and Robert Deadman Drive can see.

At the Darrell K Royal-Texas Memorial Stadium, the problem stemmed from the location of ADA ramp built at the bottom of precipitous drop. After every storm, mud was cleared from the path to provide a safe and usable ramp. One proposed solution was to increase the size of an existing retaining wall, but Landscape Services was able to eliminate erosion at about a fifth of the cost. The team dug a long trough and filled it with gravel, creating what is in essence a long raingarden for water to pool instead of flowing onto the path. The raingarden also provided a steady source of moisture so that new plants like inland sea oats could thrive without additional irrigation. The new plants also have deeper roots that function as a plant-based retaining wall.

The second case study is just north of the stadium: the outdoor space between the Music Building and Recital Hall (MRH) and Performing Arts Center (PAC). Water routinely pooled between the buildings, eroding so much soil that tree roots were exposed, the paths were often unusable, and the original infrastructure meant to redirect water was no longer functioning.

“There are problems in some parts of campus created by topography and drainage,” says Lennon. “The large, shady area between MRH and PAC is really a bathtub.”

Landscape Services drained this bathtub with methods similar to those used at the stadium. The addition of straw coir logs—an environmentally safe way to hold soil that degrades over time—to slopes with obvious erosion worked to increase soil volume so that plants could have deeper, more vigorous roots. Hundreds of native and drought tolerant plants were added to the grounds, including inland sea oats, little blue stem, and white mistflower.

“It’s important that plants not only beautify the landscape but also perform a function, as is the case with these plants we choose for erosion-prone areas,” says Jim Carse, Manager of Landscape Services. “We hope that everyone on campus can see the benefit of the outdoor spaces that we create and maintain.”

“And all the credit goes to my team who worked so diligently to complete these projects!” adds Lennon.