The Oregon Private Forest Accord and Forest Practices Act specified the methodology to develop and maintain the Statewide Flow Line data. Initial development of these data began with using best available Digital Elevation Models (DEMs) to model a synthetic stream network. Where available, lidar DEMs were resampled to a 2 meter resolution. Where lidar was not available, the National Elevation Dataset (NED, resolution of 10 meters) was used. After streams were model the Fransen fish model (Brian R. Fransen, Steven D. Duke, L. Guy McWethy, Jason K. Walter & Robert E. Bilby. 2006. A Logistic Regression Model for Predicting the Upstream Extent of Fish Occurrence Based on Geographical Information Systems Data, North American Journal of Fisheries Management, 26:4, 960-975, DOI: 10.1577/M04-187.1) was applied to predict fish presence for all streams across Oregon. Historic ODF data (maintained in the ODF Statewide Streams Fish Presence dataset) was then conflated to the synthetic streams to overwrite the fish model outputs with any valid fish survey. These data were checked by Oregon Department of Forestry (ODF) and Oregon Department of Fish & Wildlife (ODFW) GIS staff to meet minimum conflation success rates. Errors were identified and documented for future updates.

The Flow Line data will be continuously updated with fish and flow permanence surveys, following established protocols and workflows developed by ODF and ODFW. Errors in conflation with historic data, and errors in geometry from the DEM modeling will also continue to be corrected. This data should be treated as a dynamic layer, with any export product frequently updated to ensure the most current information is being used.