At the UTIA Ag Campus location, Dr. Andrea Ludwig introduces student participants to traditional challenges posed by landscapes at limiting detrimental impacts of stormwater events.
Photo courtesy of UTIA Ag

Editor’s note: This originally ran in TNA277 – Tennessee GreenTimes – Fall 2016

It’s probably no surprise that urbanization in Tennessee presents many challenges to the state and its residents as the population grows and residential areas expand through new residential and commercial developments.

The percentage of Tennessee streams listed by Tennessee Department of Environmental Conservation (TDEC) as impaired due to runoff from urbanized areas increased by 36 percent from 2004 to 2014.

Much of this impairment is due to sedimentation, or soil that is carried into surface water by stormwater.

Determining the precise source of this sediment pollution is difficult. In fact, it is commonly referred to as non-point source pollution.

So the description itself acknowledges that commercial, public and residential areas can all be expected to play a role.

One opportunity for landscape designers, municipalities and residential homeowners to reduce this pollution is by mitigating the effect of stormwater runoff on surface waters.

Where the water goes.

Designing and managing landscapes already includes horticultural and physical challenges ranging from altering sites that have poor soil quality to tailoring designs that meet a wide range of plant tastes or available light levels.

We constantly adapt to meet site and personal constraints. However, our focus is generally on plant survival and growth, aesthetics and efficiency of management, and we may not always consider the potential stormwater benefits the designed landscape can provide.

It is probably an uncommon occurrence when a resident or customer stipulates reduced water flow to a storm drain as an important landscape criterion. Indeed, this is an issue that I am becoming more and more aware of.

Before moving to Knoxville, I lived in a building that had a turf- and tree-covered, 2-acre lot able to retain almost all precipitation in most rain events.

Here, I live in a townhouse on a recently developed hillside. With every shower or storm, the storm drain right beside my living room window loudly declares that my surroundings were designed for moving water quickly away rather than mimicking nature and enabling it to infiltrate into the soil or be absorbed by plant material.

Yet infiltration into soil is really what optimal solutions are all about.

Below a campus parking lot, stormwater runoff plans were used to design an aesthetically appealing and functional water retention feature.
Photo courtesy of UTA AG

Conventional methods of managing stormwater rely on “grey infrastructure” that is sometimes called end-of-pipe.

These tools include buried pipes, culverts and concrete channels whose primary role is to redirect, concentrate and transport high volumes of stormwater runoff from yards, streets and parking lots into local waterways.

These systems usually accomplish their objective of effectively draining sites, but in the process, they have contributed to increasing stream degradation over time.

So, from landscape and stormwater professionals to residents and extension personnel, collaborative efforts addressing water management in both public and private spaces will be needed.

Often in the U.S., we use the term low-impact development (LID) to refer to the planning and practices, including bioswales, rain gardens, permeable hardscapes and green roofs, that help our built environments function more like natural ones.

Awareness of these opportunities creates chances not only for homeowners to make a difference, but also for landscape managers, designers and installers to build their business acumen while adding value to contracted installations.

From concept to reality.

To demonstrate this potential in practical field scenarios, a recent project undertaken by several collaborators on UT campuses has focused on rain gardens in underutilized spaces to illustrate the potential of LID practices to retain stormwater while enabling infiltration that reduces runoff while improving campus aesthetics.

Conventional methods of managing stormwater rely on “grey infrastructure” that is sometimes called end-of-pipe.

The goal of this project was to demonstrate the use of rain gardens and conservation landscaping techniques designed to mimic natural hydrology, prevent erosion and enhance the ecological function of the area, while also enhancing the appearance of underutilized campus landscape fragments.

Rain gardens are versatile enough to be used on a range of scales and in public and residential sites. The project was led Andrea Ludwig and Brad Collett. I had the opportunity to engage because of my outreach role to residents making decisions about managing their home landscapes.

The first site on the University of Tennessee Institute of Agriculture campus included the addition of natural stone terraces on a hillside and water-retention areas that reduce stormwater runoff to surface waters.

Building downspouts were even redirected to increase the water volume being infiltrated into the soil instead of being carried away by storm drains. The planting design mimicked a woodland plant community and emphasized use of native Tennessee plant species.

The second site, located at the downtown University of Tennessee, Knoxville campus focused on raising the height of a central storm drain to allow more water infiltration and designing a landscape that accentuated the pattern of water movement.

From landscape and stormwater professionals to residents and extension personnel, collaborative efforts addressing water management in both public and private spaces will be needed.

River rock was repurposed from another area on campus to help create a swirl pattern that provides year-round visual interest, particularly when combined with the innovative planting design.

Developing these LID sites on campus has provided the opportunity for many students, professionals and citizens to participate and experience multifunctional landscapes in action. 

Several undergraduate and graduate students across many disciplines were critical in installation as well as in maintenance of both of these sites.

Since installation, many audiences from stormwater managers to extension master gardener volunteers have toured the sites to better understand what conservation landscaping can be, and you are invited to do the same.

If you find yourself around the UTK campus, take a few extra minutes to visit these sites and see some landscapes hard at work addressing stormwater management and shifting perceptions of LID sites in Tennessee.

Bumgarner is an assistant professor and residential and consumer extension specialist, University of Tennessee plant sciences. Ludwig is associate professor, ecological engineering, biosystems engineering and soil sciences, UT AgResearch. Collett is assistant professor of landscape architecture, UT plant sciences and faculty of landscape architecture.