Description

This tabular data set represents average topgraphic wetness index compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The Topgraphic Wetness Index is a steady state index that’s used to predict areas susceptible to saturated land surfaces and areas that carry the potential to produce overland flow. The index is represented by ln (a/tan(beta)), where ln is the Napierian logarithm, a is the upslope area per unit contour length, and tan/(beta) is the slope gradient (Wolock and McCabe, 1995). The source data for average topgraphic wetness index used here was produced by David Wolock (United States Geological Survey, written communic., 2012). Units are ln(m); where ln(m) = the Naperian logarithm of length, where length is measured in meters. Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

Resources

Name	Format	Description	Link
	55	The metadata original format	https://data.usgs.gov/datacatalog/metadata/USGS.56f97be4e4b0a6037df06b70.xml
	55	Landing page for access to the data	https://doi.org/10.5066/F7765D7V

Attributes for NHDPlus Version 2.1 Catchments and Modified Routing of Upstream Watersheds for the Conterminous United States: Topographic Wetness Index

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