Data Details Page

This is a raster with 1-ft cell resolution representing a detrended version of the ArcGIS Terrain dataset, "2016 Trinity River Focal Reach Digital Terrain" (GMA 2017), which is posted at http://www.trrp.net/library/data/?id=99 . For any further details of the source data, the Terrain format data package should be referenced.

A .lyr file is included that scales coloring from -25 ft to +25 ft. 

Detrending used the DTM's "Focal_Reach_Waters_Edge_Polygon" data with a few upland impoundments removed (e.g. Union Hill Pond), plus a regional buffer to create a "hydro-planar" Terrain surface that represents the water surface from the source data (derived mainly by LIDAR, therefore representing the November 2016 water surface with 300cfs dam release. The regional buffer was created by buffering the "Focal_Reach_Terrain_Extents_Polygon" by 1,000,000 feet. Elevation for the regional buffer was set to a uniform 1596.69 ft*. Both the original DTM and this hydro-planar surface were converted to 1 ft resolution rasters. The hydro-planer raster was then subtracted from the DTM-derived raster (a DEM) to yeild this Detrended Digital Elevation Model (DtDEM). This process is detailed in the lineage section of these metadata.

* = This elevation is the midpoint between the elevation at the lower end of the DTM and the elevation of the water's edge immediately below Lewiston Dam. While this uniform elevation theoretically could make water flow out of the river near the dam (river is higher than the value of 1596.69) and into the river near the North Fork, the slope created by this is minescule. At the upper and lower ends of the river where this potential slope would be greatests, it could account for only about 0.025 ft elevation per 100 feet lateral to the river.