PSMFC has, via the StreamNet project, made several major enhancements in the PNW River Reach file which are now incorporated in the system. The major enhancement has been the addition of a new attribute which allows for the development and use of a stream based routing system.
The impetus and methodology for deriving the new stream based identifier was developed by an interagency committee that was formed under the President’s 1993 Forest Plan. The Interorganizational Resource Information Coordinating Council (IRICC), comprised of representatives from federal, state, tribal, and local entities, was tasked with developing data standards that could be used across agency boundaries that would facilitate implementation of the Forest Plan. They recognized that for stream related data, a comprehensive and regionally standard hydrologic system was necessary to ensure that data could be readily collected and shared between agencies. They further recognized that the utility of such a system would be greatly enhanced if a method for identifying a given stream within the hydrologic coverage was available. After looking at the various options available in the region, the IRICC group officially adopted the PNW Reach File system as the base hydrologic layer and developed a new attribute called the Longitude/ Latitude ID (LLID) for use in uniquely identifying streams. This attribute consists of the longitude and latitude of the mouth of the stream. All reaches (or arcs) that comprise a given stream were to be assigned a unique LLID. Longitude would precede latitude to conform with standard x,y ordering. The code will be 13 characters long, with 7 for decimal degrees of longitude and 6 for decimal degrees of latitude, with implied decimal points. After the IRICC decision, a fast track effort was put in place to add the new LLID field to the PNW Reach File and this effort is largely complete (all streams in OR and WA, all named streams in ID and MT). In the PNW Reach File a stream is defined a series of contiguous arcs comprising a waterway with identical values in the FEAT_NAME field. Only arcs representing the transport path of water (stream, braided stream, some canals, and centerlines and connector arcs within lakes and reservoirs) with a SAVENEG value of NO were included. For features that were unnamed, stream ID’s were applied visually using best professional judgment.
StreamNet has used the new LLID as the basis for building a regionally consistent stream routing system. By using this routing system, one can exploit the benefits of ArcInfo’s dynamic segmentation, including the use of event tables for data collection and sharing. We believe this is a significant enhancement to the reach file which will greatly facilitate its use.