635-412-0045 Environmental Restoration Weirs Definitions; In addition to the definitions in OAR 635-412-0005, for the purpose environmental restoration weirs the following definitions shall apply: (1) “Ancient floodplain” means channel adjacent areas and surfaces constructed by fluvial processes that functioned as floodplains or areas for overbank deposition prior to channel incision. (2) “Applicant” means a person applying for the Department’s approval of the construction of an environmental restoration weir as defined in this section. (3) “Environmental restoration weir” means one or more structures that are constructed: (a) For the purpose of delaying or slowing, but not preventing, streamflow to promote restoration of stream and habitat conditions; (b) Such that the structures do not store or appropriate water in a manner that would require a permit from the Oregon Water Resources Department; (c) To be no larger than necessary to cause overbank flooding onto the lands constituting the ancient floodplain during ordinary periods of high streamflow. Ordinary periods of high streamflow are times when the water elevations would reach the ordinary high water line in an unaltered stream condition; and (d) From wood (including untreated fence posts), earth, dirt, rock or other natural materials. Treated wood, metal, concrete, gabions or other engineered material do not qualify as natural materials. (4) “Healthy native migratory fish population” means a population of native migratory fish that, as determined by the Oregon Department of Fish and Wildlife: (a) Demonstrates appropriate life stages throughout the year; and (b) Reproduces at sufficient levels to be a self-sustaining population into the foreseeable future. (5) “Incised or eroded stream” means a stream that has been scoured by erosion to the extent that the channel bed elevation has lowered relative to its ancient floodplain and the stream has lost connectivity with the ancient floodplain, as characterized by: (a) The loss of natural wetland, riparian or meadow conditions in the adjacent surfaces; (b) The absence of overbank flooding or deposition during ordinary periods of high streamflow; (c) The loss of historic diversity of native fish or other species; or (d) The presence of dry land species that have encroached from adjacent uplands, including but not limited to sagebrush, bunch grass, juniper and pine. (6) “Qualifying stream” means an incised or eroded stream, a designated reach of an incised or eroded stream or a designated set of adjacent reaches of an incised or eroded stream that, prior to commencement of a project approved by the Department: (a) Has an estimated median monthly natural streamflow of less than one cubic foot per second during at least two months of the year; (b) Has not had a healthy native migratory fish population for at least three years prior to the time of Department approval; and (c) Is incised or eroded to the extent that the channel bed elevation has lowered by two feet or more relative to the elevation of the ancient floodplain. (7) “Reach” means a section of a stream that is similar in flow topography and habitat characteristics and is between 50 and 500 feet in length. (8) “Summit of the Cascade Mountains” means a line beginning at the intersection of the northern boundary of the State of Oregon and the western boundary of Wasco County, thence southerly along the western boundaries of the counties of Wasco, Jefferson, Deschutes and Klamath to the southern boundary of the State of Oregon. Statutory/Other Authority: ORS 509.580, ORS 509.585 & HB2298 (2021) Statutes/Other Implemented: HB2298 (2021) History: DFW 31-2022, adopt filed 03/23/2022, effective 03/23/2022