OAR 141-086-0210
Inventory Development Process and Standards
(1)
Wetland determinations conducted for the purpose of developing the LWI must be conducted according to the criteria, methodologies and guidance currently accepted by the Department (OAR 141-090 et seq.).(2)
Sources of inventory information must include:(a)
U.S.D.A. Natural Resources Conservation Service county soil survey and county list of hydric soils and soils with hydric inclusions, or other available soil surveys;(b)
NWI maps;(c)
USGS topographic maps;(d)
Federal Emergency Management Act floodplain maps, where available;(e)
Other available local wetlands inventories or wildlife habitat inventories that include wetlands;(f)
Department wetland determination/delineation files; and(g)
High resolution (1 meter or finer) color and color infrared (where available) aerial photos taken within five years of inventory initiation. The minimum photo scale must be 1 inch = 200 feet unless another scale is approved by the Department.(3)
Sources of inventory information may include but are not limited to:(a)
LIDAR (Light Detection and Ranging) topographic data;(b)
Irrigation drainage district maps;(c)
Local knowledge of area (e.g., residents);(d)
Oregon State University Institute for Natural Resources Oregon Explorer data;(e)
Department permit files; and(f)
Resource agencies, including the Oregon Department of Fish and Wildlife and U.S. Fish and Wildlife Service.(4)
Before beginning fieldwork, prepare a field map using an aerial photograph and include the approximate location of:(a)
Any wetlands, deepwater habitats, and streams from the NWI;(b)
Any wetlands from the Department’s wetland determination/delineation files or from other inventories;(c)
Hydric soils and soils with hydric inclusions (each coded separately);(d)
Wetlands or potential wetlands identified on aerial photos;(e)
Sites to visually confirm based on other leads; and(f)
Properties where access was granted.(5)
Aerial photo interpretation must be tested early in the inventory process by interpreting several wetland types, ground truthing the interpretations, and then completing the aerial photo interpretations.(6)
The local government must be responsible for requesting property access permission from landowners in the study area for parcels identified by inventory staff and/or the Department as possibly containing wetlands.(7)
All potential wetlands that are not assessed with a sample plot and other waters identified through the process described in OAR 141-086-0210 (Inventory Development Process and Standards)(1) through (4) must be visually confirmed to the extent practicable.(8)
Where property access is granted, sample plot data must be provided according to the following minimum standards:(a)
Verify each wetland with at least one sample plot that best characterizes the wetland;(b)
Verify with at least one sample plot each potential wetland where land use activities such as ditching, water diversion, or agricultural practices are likely to have significantly altered site conditions, making observations from a distance or a site walk-over unreliable; and(c)
Verify with at least one-sample plot potential wetlands with unreliable indicators (e.g., one dominant plant that grows in both wetlands and non-wetlands, such as Phalaris arundinacea).(9)
If the LWI will be used for a WCP, in addition to the requirements in OAR 141-086-0210 (Inventory Development Process and Standards)(7) and (8), a minimum of one sample plot must be provided that best characterizes each dominant wetland plant community.(10)
If the landowner denies access permission and if visual confirmation from an adjacent property or road is not possible, employ off-site wetland determination methods.(11)
All wetlands greater than or equal to one half of an acre and all wetlands identified in a Department-approved wetland delineation report must be identified and mapped as polygons. Wetlands that are less then one half of an acre may be mapped as polygons or as probable wetlands. Probable wetlands must be represented as points on the appropriate parcel(s) and should be labeled as "PW” on the maps. No further characterization or assessment is required for probable wetlands in the LWI. Probable wetlands will trigger cities and counties to notify the Department of proposed land use activities affecting mapped wetlands and other waters (ORS 215.418 (Approval of development on wetlands) and 227.350 (Notice of proposed wetlands development)). For a WCP, all wetlands one-tenth acre and larger shall be identified and mapped as polygons.(12)
The aim of the LWI is to map the location of wetlands at an accuracy of approximately 5 meters (16.4 feet). However, the actual accuracy may be less for some wetlands such as seasonal or forested wetlands that could not be visually confirmed.(13)
Each wetland must be assigned a unique identification code.(14)
All previously delineated wetlands from the Department’s files must be field-verified, if possible, to determine if wetlands are still present and are approximately the same size and configuration as when delineated.(15)
All identified wetlands must be classified:(a)
To the class level of Cowardin (and to subclass for scrub-shrub and forested classes) and must include water regime and special modifiers (e.g., “farmed” or "diked/impounded); and(b)
By dominant HGM class and subclass.(16)
When a wetland contains more than one adjoining Cowardin classification, different classes or subclasses greater than 0.25 acres in size must be mapped and labeled as separate polygons.(17)
Artificially created wetlands or other waters (such as irrigation canals and drains, industrial ponds, log ponds, golf course features, and storm water detention ponds that are greater than one half of an acre in size) must be included in the inventory regardless of their jurisdictional status, and their original purpose must be labeled on the inventory maps.(18)
Where a wetland mosaic occurs, the site must be labeled as a wetland/upland mosaic on all inventory maps and so described on the wetland summary sheet.(19)
Streams and other waters must be mapped, but no further documentation such as wetland summary sheets or OFWAM assessment is required. If an existing stream geospatial dataset is used, it may be necessary to adjust the layer to align with riparian or other linear wetlands.(20)
Using OFWAM, each wetland in its entirety must be assessed for all four ecological functions: water quality, hydrologic control, wildlife habitat and fish habitat. Any wetlands that may qualify as a Locally Significant Wetland due to education or recreation use must also be evaluated for those social functions (values) in OFWAM. The remaining functions and conditions in OFWAM do not need to be applied to any of the wetland assessment units. Contiguous wetlands or those in close proximity and assigned different codes may be grouped into a single OFWAM assessment unit based upon the guidance in OFWAM and/or in consultation with the Department.
Source:
Rule 141-086-0210 — Inventory Development Process and Standards, https://secure.sos.state.or.us/oard/view.action?ruleNumber=141-086-0210.