Streamside Restoration

CreekCare

JCWC may be able to help you manage your streamside property with our CreekCare program, if you own or manage land in the Johnson Creek watershed.

JCWC’s Guide to Streamside Restoration

Site Assessment

The first step in for riparian restoration projects is an initial site assessment. Drawing a rough sketch of the property, noting where and what types of vegetation are currently growing, can be really helpful. During the site assessment, note important compentents, such as:

  • Square footage or acreage and dimensions of the restoration area
  • Land use – is the restoration area adjacent to agricultural fields, grazing cattle, houses, manicured lawn, etc?
  • Current shade cover/level of native canopy present over the stream (this can be measured using a densitometer or an estimation of cover percentage)
  • Aspect, and amount of sun reaching the restoration area
  • Level of invasive cover (Armenian [Himalayan] blackberry, English ivy, and clematis are common). Take note of how much ground each invasive covers and how mature it is.
  • Bank condition – note undercuts, landslides, or erosion
  • General soil type and quality – sandy, clay, loamy – topsoil depth, level of contamination (litter, etc.) Is the soil compacted?
  • Flood tendencies: Is the site inundated seasonally? How often does it flood?
  • Other considerations – Beaver/nutria present? What culverts, rip-rap, or other man-made structures are present?

Invasive Plants

With the site assessment complete, the plan for restoration can take shape. Often, the first step is to remove or control invasive species. The goal is to treat invasives during the time of year that is most conducive for eradication (species dependent), and thus have the site ready for planting during the late fall, winter, and early spring.

Here’s a helpful guide: http://www.kingcounty.gov/environment/animalsAndPlants/noxious-weeds/weed-identification

For information about avoiding nesting birds when removing invasives is from a Portland Bureau of Environmental Service document:

Bureau of Environmental Services. (October 2010). Terrestrial Ecology Enhancement Guidance: Avoiding Impacts on Nesting Birds During Construction and Revegetation Projects. Version 2.

Planting

Using the initial site assessment, choose the species and amount of plants that are appropriate for each restoration site. Some riparian areas, especially along the mainstem of Johnson Creek are disconnected from the water by rip rap, and behave more like upland areas vs. riparian land. In that instance, choosing upland species for canopy cover makes more sense. Green Seattle Forest Steward Guide has in-depth information on how to plant different types of stock – bare root, plug, container and live stakes. Mulching around new plants helps retain moisture and prevents weedy species from over-crowding. Plant orders should be placed in the early fall for best selection.

Plant Species

There are several useful sources for choosing appropriate native plants for restoration projects:

The Portland Native Plant List is a great resource for hyper-local plant information. The list breaks down into sections based on plant community (Western Hemlock-Douglas Fir Forest, Mixed Coniferous/Deciduous Riparian, etc.). Information is given on habitat type, water and light requirements, growth rate and mature height/spread. While this is not a restoration-specific document, the description of which native plants thrive under what conditions is extremely valuable. The plant list goes beyond trees and shrubs, to include forbs, grasses and groundcover.

Green Seattle Forest Steward Guide, Appendix C (pg.42-44) is a short list of trees and shrubs which characterizes plants by preferred soil texture, soil moisture, sunlight, suitability for slopes, and target forest type (riparian, etc).

The Oregon State University Extension Service Guide to Riparian Tree and Shrub Planting Tables 1 and 2 characterize plants according to tolerance for flooding, drought, and shade. The tables also provide information about each species, including growth rate.

Density

Sound Native Plants has an online plant calculator that is useful for determining the amount of trees, shrubs, live stakes, groundcovers, and emergents to plant in a given area.

Clean Water Services recommends 2,000-2,600 stems/acre, and the following calculations:
Tree Stems = square footage of planting area x 0.01
Shrub stems = square footage of planting area x 0.05

Timing

Most planting occurs in the late fall, winter, or early spring, when plants are dormant. Container plants are less time-sensitive, as long as they are kept in nutrient-rich soil and watered. Seeding is best during the late summer/early fall or early spring.

Monitoring

Monitoring is an important component of adaptive management and is essential for meeting project goals. Monitoring allows managers to assess current strategies and make adjustments, while also informing future projects. The initial site assessment is the first step in monitoring. This is where the baseline conditions are established and photo points are first taken. JCWC defines riparian reforestation project success as 50% survival of planted species after five years and 10% or less cover by invasives. Some non-invasive non-native cover is considered ok.

Monitoring should occur at least once annually during the growing season and include a description of current site conditions, photo points, and an assessment of the planting and invasive species treatments. Photo points are simply photographs taken from the same vantage point at set intervals (yearly, etc.) to help assess progress. Assessment tools include transect surveys, canopy cover measurements, and visual inspection of plant health/robustness. From there, further action in the form of continued invasive treatment, additional plantings, or both might take place.

Site Challenges

Beavers

Human/Beaver conflict can arise when beavers fell newly planted trees in restoration sites. Beavers fell the majority of trees in the fall and early spring. The use of welded metal wire caging can be effective at protecting saplings. The cages should be approximately 4 ft tall and staked into the ground. There’s no need for taller caging because beavers are not great climbers. Tree cages should be removed before plants begin to grow into them (typically several growing seasons).

Beavers are particularly fond of willow stakes. We sometimes plant bare-root willow stakes deeply in the ground, so that only a few nodes are visible above ground. This allows the stakes to grow roots before being browsed by animals. Once willows have roots, they can easily re-establish if they are cut down.

Beaver Impacts and Protecting Plants:

Compacted Soil

A cost-effective way to begin building soil is to mulch with wood chips. Mulch also prevents weeds from sprouting, holds moisture, and provides a temperature buffer for plants during cold weather. Mulching may be required over several seasons.

Rocky fill or heavily disturbed soils may be removed and replaced with native soil – this option is likely prohibitively expensive. Clean Water Services suggests that once invasives have been removed, you should till the soil to a depth of at least four inches. Then add 12 inches or more of compost-amended soil that is light in texture (it soil can pass through a one-inch screen) and 35% organic matter.

Erosion-prone Slopes

Minimizing erosion during restoration is important, and each site may require different tactics. You may want to remove invasives only in small patches to avoid large areas of bare soil. Alternatively, you can use a herbicide and leave the dead plant material in the ground to keep soil stable as you establish natives. Another option is to mulch heavily, and then to lay coarse woody debris perpendicular to the slope. Biodegradable fabrics, such as coir or coconut, can stabilize slopes, too.

When planting, you can use burlap to secure plant plugs in place. If you plant species that have both deep and laterally spreading roots, they ultimately will stabilize the entire soil profile. The native plant list from Green Seattle Forest Steward Guide, Appendix C (pg.42-44) is a great resource for plants that are suitable for steep slopes.

Remember to plant small-stature native grasses that will not out-compete newly planted trees and shrubs as a temporary measure. As a long-term strategy, plant vegetation that will provide multi-level canopy to best intercept and slow rainwater before it gets to the ground.

Additional Resources

Photo by John Hamil, 2006
Backyard Habitat Certication logo

Audubon Society of Portland and Columbia Land Trust offer the Backyard Habitat Certification Program to residents of Portland and Lake Oswego. This program provides technical assistance to small-lot, private property owners to create or improve native wildlife habitat in their backyards. The program focuses on the removal of aggressive weeds, naturescaping with native plants, stormwater management, and wildlife stewardship. Visit the Audubon Society website for more information.

Scroll to Top
Our Watershed Wide Event is Coming! March 2nd, 8:45-12noon
This is default text for notification bar