421 - Comparing Stream Network from High-Resolution 3DEP DEM with NHDPlus HR Flowline: A Case Study in a West Tennessee HUC12 Subwatershed

The National Hydrography Plus (NHDPlus) Dataset was developed in 2006 and has been widely used to identify the nation’s waterbodies. An updated and high-resolution version of NHDPlus is currently under development called NHDPlus High Resolution (NHDPlus HR). According to a NHDPlus HR fact sheet, it is based upon integration of high-resolution National Hydrography Dataset (NHD) and Watershed Boundary Dataset with 3D Elevation Program (3DEP) 10-meter digital elevation model (DEM). However, the currently available NHDPlus HR flowlines do not precisely align with the stream networks observed in higher resolution DEMs such as a 1m 3DEP or LiDAR DEM. Stream networks derived from such DEMs are more suitable for extracting stream lengths, meander ratio, channel slope, etc. It is especially important for small streams that are often overlooked in large dataset such as the NHDPlus or NHDPlus HR due to their source data. Therefore, a comparison of stream network derived from 1m 3DEP DEM with NHDPlus HR is conducted in a HUC12 watershed in West Tennessee. It shows that NHDPlus HR underestimates total stream length by 40% and channel slope by 50% compared to stream network derived from 1m 3DEP DEM. Additionally, the NHDPlus HR flowlines are less sinuous along the channel meanders, hence likely underestimate the meander ratio too. The stream network derived from 1m 3DEP DEM provides attributes such as drainage area, stream order, and meander ratio which can be linked with regional regression formulas to calculate design parameters for in-stream hydraulic structures. Finally, the availability of 1m 3DEP DEM across West Tennessee presents a promising opportunity to expand the coverage of the high-resolution stream network for the entire region.