Attributes for NHDPlus Version 2.1 Catchments and Modified Routing of Upstream Watersheds for the Conterminous United States: NLCD 2011 Percent Imperviousness

This tabular data set represents NLCD 2011 percent imperviousness 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 source data is the "NLCD 2011 Percent Developed Imperviousness (2011 Edition, amended 2014) - National Geospatial Data Asset (NGDA) Land Use Land Cover" which was produced by the United States Geological Survey (Yang and others, 2011). Units are percent. 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).

本表格数据集针对美国本土，基于NHDPlus第二版数据集套件（NHDPlusv2）的两类空间分量，编译得到2011年全国土地覆盖数据库（National Land Cover Database, NLCD）不透水面百分比数据。两类空间分量分别为：1）单个河段集水区；2）经河网向上游汇流累积的河段集水区。本数据集可通过唯一标识符COMID与NHDPlus第二版数据集套件建立关联。其源数据为美国地质调查局（United States Geological Survey）于2011年编制的《2011版（2014年修订）开发用地不透水面百分比（NLCD 2011）——国家地理空间数据资产（National Geospatial Data Asset, NGDA）土地利用/土地覆盖》（Yang等，2011）。数据单位为百分比。单个河段集水区信息表征局地尺度的数据特征；经河网向上游汇流累积的河段集水区则表征上游累积的水文条件。网络累积值通过两种方法计算得到：1）分流汇流法（divergence-routed）；2）总累积汇水面积法（total cumulative drainage area）。两种方法均采用经过改进的汇流数据库，遍历NHDPlus河段网络以聚合（累积）源自河段集水区尺度的指标（Schwarz与Wieczorek，2018）。