Stream Habitat Quality Assessment
Portland State University Senior Capstone Project
Why our project is important.
Measuring the overall health of the stream is important to record over time in order to see how the surrounding environments (neighborhoods, city projects, construction, etc.) are affecting the health and quality of stream and riparian habitats. Factors such as runoff pollution, physical interferences, culverts, sewage lines, ect., can have dramatic impacts on the stream’s health. Surrounding urban environments can alter stream beds and bottoms, decrease oxygen levels, cause flash floods and change the flow of the stream.
Ultimately all of this effects the plant and animal life that depends on this habitat. These changes are recorded by the work done in our surveys and other work by the Tryon Creek Water Council. The stream’s health affects not only its inhabitants, but people’s ability to use and enjoy the park safely. Ultimately it is T.C.W.C.’s goal to get Tryon creek healthy enough to support healthy salmon populations once again.
What we assessed.
- Stream habitat surveys can help the Friends of Tryon Creek plan projects to improve habitat, such as tree planting, culvert removal, creation of slow-moving areas by placing logs in the creek or altering flow by reshaping the channel, or stabilizing banks to prevent erosion.
- These assessments are also important tools to determine the general health of a stream, and relate to salmon habitat as described below.
- Large logs create pools where young salmon live, and adults returning to spawn can rest on their journey upriver.
- Salmon need gravel for spawning: pea sized to melon sized, depending on species.
- Sediment embeds gravel, eliminating spawning areas by preventing clean water and oxygen from reaching eggs laid in gravel redds. If silt invades gravel nests, where eggs or alevin develop before emerging into the stream as fry, they can be smothered and die.
- Young salmon shelter in cobble and boulders to avoid predators and extremely cold temperature. Prey species also live in areas where the water penetrates the gravel beds. When silt embeds these areas, salmon lose shelter and food.
- Forests provide shade, drop organic material into the stream for salmon prey insects to feed on, and fallen logs to create pools
- Where the canopy opens up, sunlight allows algae to grow, which feeds different prey species
- Invasive plants can successfully eliminate native species, out competing for resources such as nutrients and sunlight as well as eliminating understory.
- Some species that grow in, or at the edge of the water produce thick, matted roots that eliminate places for salmon to feed and shelter.
- Altering flow with culverts or by removing meanders (bends) and beaver dams eliminates slow areas where young salmon live and feed
- Stream restoration activities to slow water flow can improve salmon survival
You can help improve the chances of salmon returning to thrive in Tryon Creek.
Parks and natural areas cover only about 21% of the total watershed, family housing dominates most of the rest.
Point sources of pollution in the creek include two major upper-watershed storm water outfalls draining 368 acres of the upper watershed and contributing about half of the creek’s total suspended solids.
- With the dangers posed to watershed health from urban runoff, neighborhoods can help to alleviate some of the problems through at home solutions and by pressing the city to add green streets as a replacement to impervious sidewalks.
- Green street solutions include sidewalk planters, adding more trees, or bioswales.
- Bioswales are especially good at slowing the flow of water but also help remove pollutants within the runoff through plant uptake.
- Green streets also add a much more pleasant view over the concrete jungles.
Homeowners can help on their own properties as well.
- Homeowners can disconnect their downspouts by installing rain barrels, which not only prevent water runoff from gutters instantly reaching streams but can also save money by eliminating the need for outdoor hoses.
- Solid concrete driveways and patios can be replaced with more permeable solutions, such as pavers.
- Invasive species also grow on private property. Homeowners can help by controlling invasive weeds, or by not planting invasive species in yards and gardens.
We can work together to improve the health of Tryon Creek!