Managing Aquatic Plant Overgrowth at Moorages: What Communities Are Learning
Dense aquatic plant growth is becoming a serious operational problem for several Columbia River moorages. During WOOO’s August 2026 Best Practices Forum, members compared firsthand experience with chemical treatment, cutting, tarping, and other possible control methods.
The discussion made one thing clear: there is no simple, one-time fix. Members reported that plant growth can obstruct side channels, clog boat intakes and propellers, interfere with navigation, and create an entanglement concern for swimmers. Cut fragments may drift downstream and take root in new areas, allowing a problem at one location to spread.
Approaches members have tried or discussed
- Targeted chemical treatment: One moorage reported that treatment slowed the growth but did not eliminate it. Chemical use in or near the water may require professional application and regulatory authorization.
- Cutting and harvesting: Cutting can temporarily reopen a channel, but loose plant material must be collected and removed when feasible to prevent it from drifting and re-rooting elsewhere.
- Bottom tarping: Members described tarping as labor-intensive. Plants began emerging through vent holes, gas accumulated beneath the material, and the weight used to hold the tarp in place made later removal difficult.
- Shared equipment: Participants discussed purchasing or renting harvesting equipment jointly, circulating smaller underwater cutting tools among moorings, or contracting with a commercial harvesting service.
- Increasing water movement: Because the heaviest growth appears in warm, shallow, slow-moving side channels, members wondered whether bubblers, circulators, or directional fans might help in selected locations. This idea requires technical review before use.
A practical cooperative model
Rick Nelson of The Islands Moorage is leading an effort involving seven moorages that are facing similar conditions. The group’s first goal is to compare what each community has tried, what it cost, and what results it produced. From there, the moorages can explore shared equipment, coordinated contracting, grant opportunities, and a more unified conversation with agencies.
Other waterfront communities could use the same approach:
- Identify the plant before choosing a treatment; native and invasive species can look similar.
- Photograph and map the affected area and record seasonal changes.
- Document each treatment, including cost, labor, permits, and results.
- Coordinate with nearby communities so one site’s cutting or disposal method does not worsen another site’s problem.
- Confirm permit and pesticide requirements with the appropriate agencies before beginning work.
Related resources
This entry grew out of the WOOO Best Practices Forum held August 5, 2026. It shares member experience and general planning ideas; it is not a treatment prescription or a substitute for site-specific technical and regulatory advice.
