Abstract

This data set was developed as part of the National Water-Quality Assessment (NAWQA) Program, Nutrient Enrichment Effects Topical (NEET) study. This report is concerned with three of the eight NEET study units distributed across the United States: Ozark Plateaus, Upper Mississippi River Basin, and Upper Snake River Basin, collectively known as Group II of the NEET study. Ninety stream reaches were investigated during 2006–08 in these three study units. Stream segments, with lengths equal to the base-10 logarithm of the basin area, were delineated upstream from the stream reaches through the use of digital orthophoto quarter-quadrangle (DOQQ) imagery. The analysis area for each stream segment was defined by a streamside buffer extending laterally to 250 meters from the stream segment. Delineation of landuse and land-cover (LULC) map units within stream-segment buffers was completed using on-screen digitizing of riparian LULC classes interpreted from the DOQQ. LULC units were classified using a strategy consisting of nine classes. National Wetlands Inventory (NWI) data were used to aid in wetland classification. Longitudinal riparian transects (lines offset from the stream segments) were generated digitally, used to sample the LULC maps, and partitioned in accord with the intersected LULC map-unit types. These longitudinal samples yielded the relative linear extent and sequence of each LULC type within the riparian zone at the segment scale. The resulting areal and linear estimates of LULC extent filled in the spatial-scale gap between the 30-meter resolution of the 1990s National Land Cover Dataset and the reach-level habitat assessment data collected onsite routinely for NAWQA ecological sampling. The resulting data consisted of 12 geospatial data sets: LULC within 25 meters of the stream reach (polygon); LULC within 50 meters of the stream reach (polygon); LULC within 50 meters of the stream segment (polygon); LULC within 100 meters of the stream segment (polygon); LULC within 150 meters of the stream segment (polygon); LULC within 250 meters of the stream segment (polygon); frequency of gaps in woody vegetation at the reach scale (arc); stream reaches (arc); longitudinal LULC transect sample at the reach scale (arc); frequency of gaps in woody vegetation at the segment scale (arc); stream segments (arc); and longitudinal LULC transect sample at the segment scale (arc).

First posted December 14, 2009