The Upper Chesapeake on NHDPlus HR: about 1.8 times the mapped flow paths
The Upper Chesapeake (HUC4 0206) lies in Delaware, Maryland and Pennsylvania. NHDPlus Version 2 (release 2.1) maps flow paths at 1:100,000 and NHDPlus HR mostly at 1:24,000 or finer. Over the five eight-digit basins (HUC8) compared, HR maps 17,027 km of network flow paths against 9,385 km in NHDPlus Version 2, about 1.81 times the length (02060001, HR only, and 02060008, a single 2.67 km Version 2 flowline, are left out). SWATGenX builds its SWAT+ models on NHDPlus HR; one of them sits here: Big Elk Creek at Elk Mills, Maryland (USGS 01495000).
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Transcript
This is the Upper Chesapeake, in Delaware, Maryland and Pennsylvania. Start in one of its eight-digit basins, the Chester-Sassafras. NHDPlus Version 2 maps its flow paths at one to one hundred thousand. NHDPlus HR maps them mostly at one to twenty-four thousand or finer. Across the 5 eight-digit basins both datasets carry, HR maps about one point eight times as many kilometers of flow paths: 17,027 against 9,385. We build on HR, and one of our models sits here: Big Elk Creek at Elk Mills. The Upper Chesapeake, on the network your model is built on.
Credits
Hydrography: USGS NHDPlus High Resolution; EPA/USGS NHDPlus Version 2 (release 2.1); watersheds: USGS Watershed Boundary Dataset. Map scales: EPA NHDPlusV2 User Guide; USGS Open-File Report 2019-1096. Model domain: SWATGenX model at USGS 01495000.