S. Taylor Jarnagin

Changes in anthropogenic impervious surfaces, precipitation and daily streamflow discharge: a historical perspective in a mid-atlantic subwatershed

Aerial photography provides a historical vehicle for determining long-term urban landscape change and, with concurrent daily streamflow and precipitation records, allows the historical relationship of anthropogenic impervious surfaces and streamflow to be explored. Anthropogenic impervious surface area in the upper Accotink Creek subwatershed (near Annandala, Virginia, USA) was mapped from six dates of rectified historical aerial photography ranging from 1949 to 1994. Results show that anthropogenic impervious surface area has grown from approximately 3% in 1949 to 33% in 1994. Coincident to this period, analysis of historical mean daily streamflow shows a statistically significant increase in the streamflow discharge response (per meter of precipitation) associated with “normal” and “extreme” daily precipitation levels. Significant changes were also observed in the frequency of daily streamflow discharge at given volumes above and below the historical daily mean. Simultaneously, the historical magnitude, frequency and pattern of precipitation values ≥ 0 mm, ≥ 6.0 mm and ≥ 35.0 mm show either no statistically significant change or influence on streamflow. Historical changes in streamflow in this basin appear to be related to increases in anthropogenic impervious surface cover. Historical aerial photography is a viable tool for revealing long-term landscape and ecosystem relationships, and allows landscape investigations to extend beyond the temporal and spatial constraints of historical satellite remote sensing data.

A Modeling Approach for Estimating Watershed Impervious Surface Area from National Land Cover Data 92

We used National Land Cover Data 92 (NLCD 92), vector impervious surface data, and raster GIS overlay methods to derive impervious surface coefficients per NLCD 92 class in portions of the Mid-Atlantic physiographic region. Sample areas for the study were thirty-six subwatersheds ranging in size from 2 km 2 to 150 km 2 . A three-category rural-to-urban gradient design was utilized due to the changing sub-pixel relationship of impervious surface areas within developed/nondeveloped areas. A gradient rule based on the NLCD 92 DEVELOPED% defined the sample areas as “rural” (� 18 percent ‘developed’), “intermediate” (18 percent‐40 percent ‘developed’) and “dense suburban” (40.01 percent‐80 percent ‘developed’). The gradient scheme produced three separate sets of coefficients per NLCD 92 Level 1 and Level 2 class. Results show distinct per-class coefficient groupings across the rural-to-urban gradient with coefficients directly related to the increasing level of development in a subwatershed. We also developed a linear equation between the NLCD 92 DEVELOPED% and truth percent impervious area. Results show a relative accuracy of approximately 80 percent and a mean absolute TIA% estimate error of approximately 2.0 percent � 1.0 percent for both the Level 1 coefficients and the Level 2 coefficients. Results derived from the linear regression model show a relative accuracy of 70 percent with a mean absolute TIA% estimate error of approximately 2.0 percent � 1.0 percent. This suggests that a linear model can be used as a rapid assessment tool to approximate TIA% from NLCD 92 data. Results are based on a spatial aggregation of pixels to the subwatershed or “whole-area” scale and are most applicable to “pour-point” models utilizing a single percent impervious surface area parameter. The models reported here have been tested only in the Mid-Atlantic region (USEPA Federal Region 3).

Regional and Global Patterns of Population, Land Use, and Land Cover Change: An Overview of Stressors and Impacts

This paper provides an overview of land use and land cover (LULC) change and regional to global patterns of that change and responses. Human activities now dominate the Earths global ecosystem and LULC change is one of the most pervasive and influential activities. LULC change alters nutrient cycling, hydrology, ecology, ecosystem and community functioning, species diversity, and enhances the spread of invasive species and communicable disease. Drivers of LULC change and methods of quantification are discussed. The discussion does not attempt to examine in detail the specific consequence of each potential change in land use and land cover at a global scale. Rather, it concentrates on the human drivers of land use and land cover change, regional patterns of change, and their resulting stressors and ecological impacts.

Mapping spatial thematic accuracy with fuzzy sets

Common thematic map accuracy measures (e.g., error matrix and kappa coefficient) are inadequate for analyzing the spatial variation of thematic map accuracy. This paper presents a method of mapping spatial accuracy of thematic land cover maps using fuzzy sets. First, we define a multi-level agreement between reference data and corresponding pixels on the map. Next, we formulate a discrete, multi-level agreement fuzzy set regarding a particular land-cover type for each pixel on the map. Then, we construct spatial accuracy maps based on information from the multi-level agreement fuzzy sets. We illustrate the method by constructing accuracy maps of several land cover types for the Mid-Atlantic Regionregion. Results show that thematic map accuracy is not spatially homogenous, but varies across a landscape and different land cover types having different spatial patterns of accuracy. The method provides valuable information about thematic map accuracy for both scientists and decision makers, such as in designing adaptive sampling schemes, deriving landscape indicators, or thematic map-based modeling.

Effectiveness of landscape-based green infrastructure for stormwater management in suburban catchments

U.S. Environmental Protection Agency ORD/ NERL/SED/Ecological and Human Community Analysis Branch, Research Triangle Park, NC 27711, USA National Socio‐Environmental Synthesis Center (SESYNC), Annapolis, MD 21401, USA Correspondence Sean A. Woznicki, U.S. Environmental Protection Agency ORD/NERL/SED/ Ecological and Human Community Analysis Branch, Research Triangle Park, NC 27711, USA. Email: woznicki.sean@epa.gov