Those lucky enough to have a stream on their property know it can become a mixed blessing. Over time, changing stream conditions may bring erosion and related problems. Fortunately, there are methods to reverse a stream’s demise and bring it back to being a natural asset once more.
Two Penn State Extension specialists — Tyler Groh, an assistant research professor and watershed management specialist, and Danielle Rhea, a water resources educator in Jefferson County — conducted a webinar about stream issues during the virtual 2021 Pennsylvania Farm Show last week.
They reviewed how a healthy stream can develop eroded banks, with soil from the property turning into sediment swept away downstream. More importantly, they described ways to avoid or correct these concerns.
Groh said that, in an ideal natural environment, rainfall results in 50% deep infiltration into the soil, 40% evaporation into the atmosphere and 10% runoff into waterways.
As natural ground cover morphs into more impervious coverage due to compaction or hard manmade surfaces, that ratio of this “water budget” can change to just 5% shallow penetration, 30% evapotranspiration and 55% run-off, resulting in a major change in stream flow. As a result, channel evolution begins to occur.
What was once a relatively shallow stream flowing through a stable, gently terraced channel can gradually scour the stream’s bottom, so that the stream’s bank heights become taller.
Groh said that it only takes a 1-foot increase in streambank height for those banks to become unstable. As the scouring cycle continues, headcutting occurs, the stream bottom widens out within its steeper banks in an effort to restabilize, finally leading to a shallow stream once more. But it turns into a stream that flows within steep terraced embankments with a floodplain separating it from its new banks.
To halt this cycle, the initial step that Groh recommended is diagnosis using the First Evaluation of Stream Health or “FISH Protocol” available at https://fishprotocol.org/. This self-evaluation leads the stream owner through the process of looking at and recording several indicators.
“Water clarity” evaluates the stream water’s transparency by measuring soil particles and algae suspended in the water, using a transparency tube to determine the turbidity.
“Embeddedness” looks at stream bottom habitats to determine if stones and rocks there have bare spaces between them or the degree to which they are covered by mud and sand.
Looking for the number and types of macroinvertebrates present when rocks are flipped over provides a read on stream life; if only organisms like midge larva and pupae, aquatic worms and pouch snails are present, the stream is in trouble.
Since well-established vegetation on streambanks provides stability and can prevent bank erosion, the FISH Protocol also asks the property owner to evaluate the vegetation providing bank cover on both sides of the stream. Also recorded is vegetation like trees and shrubs in the riparian zone adjacent to the streambanks.
The FISH Protocol’s results will point the property owner to stream repair options for rehabilitating and stabilizing the streambank.
The simplest and cheapest option is to let the streambanks grow wild. But this approach can allow undesirable or invasive plants to take over, and it presents a weedy appearance initially. And, it takes longer for plants to mature and provide their stabilizing benefits.
A more proactive approach is to plant native vegetation buffers along the streambank. Although it takes time for a buffer to develop and start slowing water run-off entering the stream, providing pollution interception and offering wildlife habitat, its advantages are its cost effectiveness and that, generally, no environmental permits are required.
Another more complex option likely requires technical assistance and involves grading the streambank to a 3:1 slope. For example, a 2-foot existing streambank would require grading back 6 feet from the stream. Then, native vegetation is planted in prepared seedbeds and trenches are dug to secure erosion control matting. This type of stream disturbance requires permitting by the Pennsylvania Department of Environmental Protection.
Groh emphasized that — aside from cleaning litter and natural debris from streams and culverts without using heavy equipment, and adding trees or other plants on streambanks and in riparian buffers — most other stream restoration and stabilization work is subject to Pennsylvania’s Chapter 105 regulations regarding water encroachment permits issued by DEP.
If working on less than 500 feet of continuous stream banks, and adding rock or other non-polluting structures to a stream’s bank or channel, a General Permit 3 is required.
Groh suggested that property owners contemplating streambank work first touch base with their local Conservation District for further guidance.
Rhea discussed selecting the right plants for streambanks and buffers.
Since “not every plant is going to do well in every location,” she recommended matching plantings to the site’s characteristics and using native plants whenever possible, since they are more likely to survive, thrive and provide better habitat for wildlife and aquatic organisms.
Looking at existing plants along the stream also is a guide as to what will grow well there. And perhaps some of those types of plants can even be transplanted into the stream area.
When choosing plants for around streams, soil moisture tolerance, sun exposure needs and size at maturity are other important considerations, according to Rhea. Non-woody plants like ferns, grasses and perennials, such as blue flag iris and pickleweed, are able to bend and move, which allows them to withstand flooding conditions. This makes them ideal for placement near the water’s edge. Optimum planting time for these herbaceous plants is in spring after the last frost.
Rhea highlighted live stakes as a “lots of bang for your buck” way to introduce woody plants like silky dogwood, pussy willow, elderberry and American sycamore to riparian buffers. Live stakes, available from nurseries or harvested from existing healthy plants, are cuttings from dormant native trees and shrubs best planted in early spring or late fall. They root readily in moist soil if a pilot hole is dug at a 90-degree angle to the soil slope and the plants are then placed in a zigzag pattern at 2 to 3 feet spacing.
Rebar makes a good tool for making pilot holes, Rhea said.
In drier soil, Rhea suggests bare root and containerized plants like black-eyed Susans, butterfly weed, Eastern redbuds and Eastern white pine. These are available from nurseries or can be transplanted as seedlings. Bare-root tree and shrub seedlings should be planted in early to mid-spring, while containerized trees and shrubs can be planted in spring or fall.
The streambank plantings’ survival rates improve when using tree shelters with bird nets, landscape fabric mats around tree bases, and mulch around shrubs.
Ongoing maintenance includes periodic inspection of the streambank plantings’ status, being on the lookout for invasive plant species like tree of heaven, thistle and multiflora rose, along with weeding and/or herbicide applications. Mowing to 6 inches in height in late fall or early spring is also a good practice, Rhea said.
For more detailed information, Penn State Extension is offering a five-part Backyard Stream Repair webinar series Tuesdays between Feb. 9 and March 9 at 2 p.m. Go online to extension.psu.edu/backyard-stream-repair-series for complete details and registration.