Thursday, officials with the Austin Watershed Protection Department are expected to provide an update on the work they’ve done since a landslide destroyed backyards and a popular trail in the center of Austin.
About two weeks ago, heavy rained wiped out four backyards and sent debris tumbling down the hill on to Shoal Creek Trail near North Lamar Boulevard.
What city officials call a “slope failure” destroyed hundreds of feet of the popular walking and biking path.
“It is a little scary that that could happen so close to us, especially since our house is on the hill,” said Misty Reid, who lives near the trail.
She told us she knows erosion is a big issue in that area, but was still surprised to see one night of heavy rain caused this much damage.
But experts like Joel Johnson, associate professor of Geological Sciences at UT Austin, say “It’s not entirely surprising that there was erosion there.” He said it’s disturbing that it happened, but that location is at higher risk of erosion.
Johnson showed us a map that demonstrates what kind of material the ground is made up of in different parts of Central Texas. We then compared that map to the Watershed Protection’s erosion risk map.
“The highest erosion risks are in the middle of town, away from resistant limestones,” explained Johnson.
He said movements dating back millions of years caused softer materials to shift toward the southeastern part of Austin, which means stronger materials like limestone remained in areas to the west.
According to Johnson, areas toward downtown and southeast Austin have “basically sediments, sand and gravel and clay that hasn’t even really yet turned into rock that was deposited by the Colorado River and tributaries.”
Johnson continued to explain while pointing toward the Hill Country, “The bedrock you see up through here is more resistant limestone that basically can support steeper slopes without failing.”
But even in higher risk zones, Johnson told us there’s no need for homeowners to panic.
He said there’s no perfect solution to erosion, but engineering work can help reduce risks.
Johnson said there are ways to divert the flow of water, so it doesn’t flow down the most vulnerable parts. Engineers could also drill into the slope and help with drainage.
“We definitely employed several engineers including a water expert, mainly because we do get so much water on our property,” said Reid.
Many homeowners told us they’re glad they took those steps, and they hope they will remain effective. “Whenever you do preventative work, you never think it’s going to be needed,” Reid said. “So to hear about this definitely makes me thankful that we took the time to do that.”