Delaware River Basin Catchments Based on Strahler Stream Order 1 from National Hydrography Dataset (NHD) Stream Centerline Features for 8-digit HUC

In 2012, catchments were generated in the Delaware River Basin for 8-digit HUCs in the areas underlain by the Marcellus Shale (all of 02040101, 02040102, 02040103, 02040104; and headwater areas of 02040106 and 02040203) based on the National Hydrography Dataset (NHD) Strahler first- and second-order streams. There were areas that did not have a catchment generated so another methodology needed to be used in an attempt to fill in the 'gap areas'. A 900-cell, flow accumulation raster generated for the Pennsylvania StreamStats application was used as a surrogate stream layer with the same Strahler ordering system applied to help fill in the 'gap areas'. Points were manually placed at the downstream end of the Strahler Order 1 and 2 reaches using the surrogate streams as a guide. This manual point placement is different from the automated method used to develop the catchments generated from the NHD flowlines. The manual placement of the catchment pour points does not include a point downstream of a confluence, therefore, not as many catchments are generated in the 'gap-area' processing. The naming convention of directories housing the geospatial datasets is based on 8-digit Hydrologic Unit Code (HUC) designations. Directories 02040101 through 02040106 correspond to HUCs in the Upper Delaware Basin and directories 02040201 through 02040207 correspond to HUCs in the lower Delaware Basin. The directories and corresponding descriptions are: 02040101 - Upper Delaware. NY, PA; 02040102 – East Branch Delaware. NY; 02040103 – Lackawaxen. PA; 02040104 – Middle Delaware-Mongaup-Brodhead. NJ, NY, PA; 02040105 – Middle Delaware-Musconetcong. NJ, PA; 02040106 – Lehigh. PA; 02040201 – Crosswicks-Neshaminy. NJ, PA; 02040202 – Lower Delaware. NJ, PA; 02040203 – Schuylkill. PA; 02040204 – Delaware Bay. DE, NJ; 02040205 – Brandywine-Christina. DE, MD; 02040206 – Cohansey-Maurice. NJ; 02040207 – Broadkill-Smyrna. DE. The naming convention for shapefiles is based on the following: 1) 8-digit HUC designation 2) str1_ (Strahler stream order 1) or str2_ (Strahler stream order 2) _mgp (manual gap dataset using interactive processing) 3) _new (new dataset using automated processing) 4) 18 (shapefile projected into Universal Transverse Mercator (UTM), Zone 18, North American Datum (NAD) 1983, projection). The following four names are examples: 02040101str1_mgp18; 02040103str2_mgp18; 02040206str1_new18; 2040207str2_new18. The two processing times are “new” which is an automated process, documented in the metadata for each shapefile, to generate catchments based on 1:24,000-scale NHD streams and “mgp” which is a manual, interactive process, documented in the metadata for each shapefile, to generate catchments to fill in the gaps (created by new processing) based on a flow raster from the PA StreamStats application. Not all directories have “new” and (or) “mgp” datasets. In 2012, automated processing for Strahler order 1 and 2 catchments was completed for 8-digit HUCs with Marcellus Shale (02040101 – 02040104, 02040106, headwaters of 02040203). Additional processing was completed between September 1, 2015 and September 30, 2016 for HUCs 02040101 through 02040104 and 02040106. As a result HUCS 02040101 through 02040104 and 02040106 have only mgp datasets for Strahler order 1 and 2. Due to the large tidal areas with low relief in HUCs 02040201, 02040202, and 02040205 through 02040207 only new processing was conducted. HUC 02040204 is the Delaware Bay water body. Non-tidal areas in HUCs 02040105, 02040201, 02040202, and 02040205 have both new and mgp datasets. HUC 02040105 had a very small tidal area with more measurable relief, therefore, new and mgp processing were completed. FGDC-compliant metadata specific to each shapefile can be found in files with the .xml extension.