Description: The RMZ is measured from the wider of the centerline (when the stream is represented by a line), stream edge (when the stream is represented by a polygon), or outside edge of an observed migration zone (OMZ). The OMZ was created specifically for this effort to map RMZs by combining existing data sources showing mapped stream locations which included (a) the National Hydrography Dataset (NHD) area polygons, (b) NHD waterbody polygons (e.g., lakes, ponds, sloughs, deltas) which intersect streams, (c) WDFW 2017 Visible Surface Water area polygons, and (d) areas marked as river in the NRCS soils data used to develop SPTH200. The OMZ is not a substitute for the channel migration zone (CMZ); rather, because no statewide dataset for CMZs currently exists, we created OMZs using existing data to enable the mapping of RMZs, knowing that in many instances the OMZ will be narrower than the CMZ. The dataset is subject to change as better base data becomes available. Caution: These data are a modeled representation of RMZs developed using GIS data and remote sensing datasets. As such they are estimates of RMZ locations and not surveys of known RMZ locations. This regional dataset was developed for analytical purposes and can be used to estimate the total area, distribution, or patterns of RMZs at a landscape scale (for example, county or watershed). This dataset is not intended to support site-scale land use decisions – other than for use as a flagging tool to determine where site surveys are necessary. True delineation of RMZ boundaries for any sitescale land use decisions require a field survey to verify a RMZ’s presence, boundary, and quality.
Copyright Text: Washington Department of Fish and Wildlife