Our Knotweed Control Projects - Beaver & Latourell Creeks
 Knotweed |
What is Knotweed and Why is it a Problem?
Knotweed is highly invasive and is a very difficult weed to control. It has an enormous root system, which makes manual control methods ineffective and time consuming. One study showed that even when the knotweed stems are cut back to the ground every 4 weeks all summer long for three years, the roots continue to live and send up new shoots. Other studies show that cutting the stems actually stimulates dense re-growth. For this reason, herbicides must be used to effectively control this plant. Knotweed prefers wet soil and causes the biggest problems near streams where it can quickly take over as high waters and floods distribute it throughout a watershed. Since herbicide use near streams is tricky, we offer help controlling knotweed in these areas. For more detailed information about knotweed's negative impacts and help identifying it, visit our knotweed page.
Where We Work
Our knotweed control work is focused in two watersheds: Beaver Creek, a tributary to the Sandy, and Latourell Creek, which flows into the Columbia.
We Need Your Help
If you live along either of these creeks we will be asking for your permission to look for knotweed and to treat it where we find it. Without the cooperation of landowners, we would not be able to protect these creeks from this devastating weed. If you have already granted us permission, thank you. If you have not, please contact us as soon as you can.
Beaver Creek
The Nature Conservancy has been working on knotweed control for several years in the Sandy River Watershed and their efforts have drastically reduced the amount of knotweed in this watershed. They approached us a few years ago to ask us if we could help out in one of the tributaries to the Sandy River, Beaver Creek. We agreed and began survey and control efforts in the Beaver Creek Watershed in 2007.
Beaver Creek Knotweed Mapping and Control Results |
|
| Creek side properties in the watershed | 359 |
| Creek side private properties in the watershed | 286 |
| Properties surveyed | 322 |
| Properties we are not able to survey (need permission) | 29 |
| Properties with knotweed | 25 |
| Landowners that gave us permission to treat knotweed | 22 |
| Properties treated to date | 22 |
| Square meters of knotweed before our project began | ~2375 |
| Square meters of knotweed treated to date | ~2350 |
| Percent decrease across all patches treated in 2007 | 96% |
| Average percent decrease per patch for patches treated in 2007 | 89% |
We began by contacting the owners of the 359 properties along Beaver Creek. So far we have conducted extensive, riparian surveys on 322 of these properties and knotweed was found in 25 locations. Luckily, knotweed's downstream spread from most of these patches was minor or had not yet occurred. By utilizing The Nature Conservancy's successful approach, we were able to reduce the amount of knotweed by 96% across all patches treated in the first year of our project. This project's survey and control efforts came just in time. The amount of knotweed found within the Beaver Creek Watershed can be controlled without a huge investment. It would have been much more costly if we had waited another two years or more before beginning our control work. If you have received a mailer from us requesting to survey your property for this weed and have not yet returned a permission form, please contact us as soon as you can. Look over the table below for detailed data on our knotweed control work in the Beaver Creek Watershed.
All knotweed patches that the District currently has permission to treat will be treated at least once between spring and winter 2009 and as needed in subsequent years. A strong effort will also be made in summer 2009 to gain permission to survey the remaining 29 properties that have not been surveyed and to obtain permission to treat the remaining knotweed patches.
Latourell Creek
The Latourell Creek Watershed is a small watershed located in the Columbia River Gorge draining just over 2,700 acres and flowing through only 36 properties, 17 of which are privately owned. The watershed's most well known feature is Latourell Falls, a 249 foot waterfall located just over 2 river miles above the confluence with the Columbia River. Just below the falls, the Creek flows through the eastern edge of the village of Latourell, into a large wetland area and then flows under Interstate 84, entering the Columbia River at the western edge of Rooster Rock State Park. Over 40 percent of the watershed lies within the Columbia River Gorge National Scenic Area.
Knotweed surveys were initiated during the summer of 2008. The owners of all 36 creek side properties were contacted and permission was obtained to survey the creek on all properties but two. Knotweed was found in only four patches on three properties and all patches were at the upper end of the watershed. Although the patches were near the creek, knotweed had not yet invaded the creek bank where it could be dislodged and spread by high waters. One patch was found just in time, a 680 square meter patch was growing just a few meters from one of the headwater springs.
Permission was obtained to treat all patches found within the watershed and all patches were treated. The four patches treated were all very large, totaling 2,246 square meters, nearly as much as was spread throughout the entire Beaver Creek Watershed prior to our knotweed control project there. All previously treated knotweed patches will be re-treated at least once between spring and fall 2009 and as needed in subsequent years. A strong effort will also be made in summer 2009 to survey the remaining two properties that have not yet been surveyed.
