AUSTIN (KXAN) — Meteorologist Sean Kelly spoke with Doctor Brent Bellinger at Emma Long Park along Lake Austin to discuss how runoff from flooding rain plays a role in erosion and lake quality. Doctor Brent Bellinger is the Conservation Program Supervisor with the city of Austin’s Watershed Protection Department. Dr. Bellinger said Central Texas is located in ‘Flash Flood Alley’ our waterways are a haven for changing frequently and quickly.
“And those types of large events, mobilize a lot of sediments and other material off of the landscape into our waterways.” Dr. Bellinger said that runoff flowing into our lakes from heavy rain events is inevitable. It is, after all, a vital part of filling up our Highland lakes which is critical in maintaining our water supply. It is, however, very important to make sure the pace at which runoff is flowing isn’t too fast. Bellinger’s mantra, ‘slow the flow'”.
How can this be done? Runoff can naturally be slowed down by vegetation. Private shorelines however have played a role in ridding their lawns of its natural vegetative state and therefore increasing the speed of runoff which overall is negatively influencing the health of our lakes. There is a strong connection between the quality of a waterway and the number of residential developments there are along the coast.
“It’s where you’ve disturbed the landscape, through lawns, removal of vegetation, and you’re mobilizing not just sediments, but also fertilizers, herbicides, pesticides, everything else that goes kind of with it, when you have lawns or, you know, runoff of parking lots, that are bringing in other contaminants moving into our systems,” Bellinger said.
The result is a change in health and overall quality of the water, which has major impacts on aquatic life.
Doctor Bellinger said, “Your lakes become imbalanced, ecologically speaking, and so then you get nuisance plant growth, you get nuisance and potentially toxic algae growth. And that’s being fed by all these large inputs coming off of the landscape.”
Another negative result of fewer native plants and vegetation along a coast is increased coastal erosion. As Austin’s population continues to grow, and boating activity within our lakes increases, erosion has been found to be more of an issue, especially along private properties that removed their vegetation buffer. Native vegetation along a coast is crucial to not only block and filter what’s flowing into the water (runoff) but acts as a buffer to absorb much of the movement and wake that’s coming from boats inside the water. Being able to absorb a boat’s wake on the edges not only limits coastal erosion but it helps preserve the aquatic plant and marine habitat that thrives in these areas.
Doctor Bellinger said there was a time when vertical concrete seawalls were able to be constructed on properties. This only exacerbated the wake energy, which further stirred the sediment and made aquatic life inhabitable. “What it does instead is it re-suspends the fine material and moves it away. What you’re left with is just a lot of sand that doesn’t support much animal life. It’s very abrasive to the bugs… The waves will keep eroding back those shorelines and it’s going to transport that sediment material that you have a shoreline somewhere else in your water” Dr. Bellinger said.
Luckily the city now requires property owners to have more of a 45-degree angle leading up to their shoreline in combination with using natural materials.
“And then we also require native vegetation get planted. And this provides a great reduction in the wave energy. So you’re not getting that resuspension, you now have a lot of microhabitats for algae for plants for bugs for little fish that are here. And then along the shoreline, with that natural vegetation, you’ve kind of reconnected, the lake and the land.”