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All wetlands greater than or equal to one-half of an acre and all wetlands identified in a Department-approved wetland delineation report are required to be identified and mapped as polygons with a goal accuracy of +/- 25 feet (developed under pre-2009) or +/- 5 meters (developed under 2009 rules).SWCA used ArcGIS to prepare base mapping for the study area in accordance with the standards outlined under OAR 141-086-0210 (Inventory Development Process and Standards). Data were reviewed to identify tax lot parcels that contained potential wetlands, and to generate a list of landowners for which access requests were made by the city. For field use, D-size (22 × 34 inches) map series were printed at a scale of 1 inch = 200 feet, and included a selection of suitable mapping layers.Scanned DSL maps of wetland polygons that had previously been identified in the same township section and ranges as the study area were obtained directly from DSL by request. These maps were reviewed by the City, and wetlands that were found to be located within the study area were manually converted to digital format for incorporation into the project geodatabase. Where possible, these wetlands were visually confirmed, and where deemed necessary, additional sample plot data were collected.Subsequent to creating the base maps for the inventory, SWCA created an ArcGIS georeferenced database to house spatial data, attribute tables, and metadata for the study. The LWI geodatabase contains attributes that record expanded comments and data source information relating to each wetland. The geodatabase is projected using the Oregon Lambert conformal conic.Using the off- and on-site methods, wetland and water features were mapped and characterized. GPS-collected field data were post-processed to ensure sub-meter accuracy, and polygons that were sketched on printed field maps were digitized to an approximate accuracy of 5 meters (16.4 feet), where visibility was available.Further information on the LWI development and results can be found in the City of Medford Urban Reserve Local Wetlands Inventory report at https://www.oregon.gov/dsl/WW/Pages/Inventories.aspx. |