Flow accumulation grid generated from 2011 LiDAR 1 meter bare earth DEM, Blue River Watershed

This dataset has been derived from the Blue River 1 meter LiDAR data. The values represnt the number of cells (1 meter by 1 meter) that drain to the cell. This data is used to derive stream and watershed layers. Output cells with a high flow accumulation are areas of concentrated flow and can be used to identify stream channels. Output cells with a flow accumulation of zero are local topographic highs and can be used to identify ridges.

This dataset represents the Blue River Watershed survey area in Linn and Lane County, OR. This bare earth digital elevation model (DEM) represent the earth's surface with all vegetation and human-made structures removed. The bare earth DEMs were derived from LiDAR data using TIN processing of the ground point returns. The DEM grid cell size is 1 meter. The elevation units are in meters. Some elevation values have been interpolated across areas in the ground model where there is no elevation data (e.g. over water, over dense vegetation). Watershed Sciences, Inc. collected the LiDAR and created this data set for the EPA and USFS.

In some areas of heavy vegetation or forest cover, there may be relatively few ground points in the LiDAR data. TINing the points produces large triangles and hence the elevations may be less accurate within such areas. Elevation values for open water surfaces are not valid elevation values because few LiDAR points are returned from water surfaces. Triangles were created across water surfaces by interpolating from the nearest land points.