Why was the national database created on a HUC by HUC basis rather than creating the database in one large output file?
A. If software and hardware capabilities had been up to the task, processing of the EDNA Stage I layers would have been done in one pass; processing the entire NED into hydrologic derivatives in one large piece. However, the NED data, which forms the basis for the EDNA database, is a very large Digital Elevation Model (DEM), requiring almost 60 GB of disk space for the conterminous United States alone. The size of the problem required a unique solution.
