Levees and Revetments
Over 500 levees and revetments exist along King County rivers. Inspections and maintenance occur regularly on these river facilities.
Levee and revetment monitoring and maintenance activities include:
Some levee and revetment access roads and slopes are mowed to allow crews to inspect these facilities during and after flood events. This mowing is generally done in the late fall, just before the winter flood season.
Access Control and Maintenance
Gates and gravel roads are maintained on most river facilities. Access road resurfacing is rare, and is usually accomplished in conjunction with a major maintenance project. Gates that limit public access to river facilities are occasionally repaired or replaced.
Control of Invasive Plant Species at Project Sites
In order to improve the success of bioengineered facility repairs, comply with state noxious weed regulations, and in some cases, meet specific permit requirements, invasive species are removed from project repair sites and areas where listed noxious weeds are present. The species most commonly encountered include Blackberries, Japanese and/or Giant Knotweed, Knapweed, Tansey, and Scot's Broom. In most cases weeding has been accomplished through hand labor, however in limited cases herbicides are used. A licensed technician does all of the herbicide application.
In order to improve the success of bioengineered facility repairs, most projects are irrigated weekly during summer and early fall for two years after the completion of each project. A one or two person crew typically does the irrigation using a gasoline-powered pump to withdrawal water from the river. The pump intake is screened in accordance with WDFW standards and all withdrawals are documented per a water withdrawal permit issued by the Washington State Department of Ecology.
Annual inspection of recent facility repair sites is used to determine revegetation needs. Revegetation is accomplished by hand crews and typically involves transplanting native species from one- or two-gallon pots. Revegetation needs are identified in late summer and planting occurs in the fall or winter.
Hazardous Tree Removal
Trees do occasionally fall across access roads or pose a threat to those using the roads. These trees are either removed entirely, or moved to the riverward side of the facility.
Facility Inventory and Assessments
Levees and revetments are inspected on a regular basis. Routine facility assessments help identify and prioritize maintenance needs.
Logjams are removed only if they pose a direct threat to certain types of property, and can be removed without endangering personnel or equipment. When logjams are moved, the woody debris is usually dislodged and but back into the river.
For questions about Levee and Revetment Maintenance, please contact John Koon, Engineer, River and Floodplain Management Section.