Browsing by Author "James Gregory, Committee Member"

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Impervious Surface Cover: Effects on Stream Salamander Abundance and A New Method of Classification Using Feature Analyst.
(2005-12-06) Miller, Jennifer Elizabeth; Christopher Moorman, Committee Member; James Gregory, Committee Member; Stacy Nelson, Committee Member; George Hess, Committee Chair
Increasing impervious surface cover associated with urbanization degrades water quality and alters wildlife habitat. Forested riparian buffers are one popular method of mitigating the effects of impervious surface cover. My study was designed to investigate the effects of impervious surface cover and forested riparian buffer width on the abundance of larval southern two-lined salamanders (Eurycea cirrigera). I sampled 50-meter reaches of 43 streams, representing the range of impervious surface cover and forested riparian buffer width combinations across Wake County, North Carolina, USA in 2004. Additionally, I measured physical and chemical stream properties to account for local habitat effects. Percent impervious surface cover in the catchment, percent detritus cover in the stream, percent pebble substrate in the stream, and average water conductivity were significant predictors of larval E. cirrigera abundance. Forested riparian buffer width was not a significant predictor. Larval E. cirrigera abundance was lower than anticipated in several streams that appeared to provide good habitat. I discovered that salamander abundance was low in intermittent streams with substrate that is highly sedimented below the surface layer. I suspect that intermittency combined with filled substrate interstices reduced the ability of salamanders to migrate with the water column during dry periods, resulting in low abundances. My research is consistent with a growing body of literature documenting the negative effects of impervious surface on stream biota. In my study, low flow events significantly affected larval E. cirrigera abundance. My findings also suggest that salamander abundance cannot be predicted by measuring the forested buffer width only at the sampling location. A catchment-wide quantification of the stream buffer system, accounting for culverts and other breaches, might yield a better predictive model. Environmental, economic, and resource management research and decision-making requires current, accurate spatial information. Mapping with aerial imagery can play an important role in providing such information, if it can be done in a cost effective and accurate manner. For my research, I needed an efficient technique for identifying impervious surfaces in urbanizing Wake County, North Carolina, USA. The objectives of my study were to develop an accurate classification of impervious surface using high-resolution aerial imagery and to provide insight into the practical application of Feature Analyst, an object-oriented classification extension within ArcGIS. Feature Analyst utilizes advanced, object-oriented classification algorithms that incorporate spatial context with color and tone to classify high-resolution imagery. I trained Feature Analyst to differentiate pervious and impervious surfaces and classified 111 United States Geological Survey images with a spatial resolution of 33-cm. My classification results yielded an overall accuracy of 92%, with a user's accuracy of 95.2% for the impervious surface class. These results show improvement over historical accuracies of 85% or less. Feature Analyst is most beneficial when spectral value alone will not distinguish classes, object-oriented output is desired, and the time or knowledge for developing complex, customized algorithms is unavailable. I recommend Feature Analyst for classification of high-resolution imagery when object-oriented output is desired and hand-digitizing is impractical.
Physical and Economic Constraints on Wetland Mitigation Sustainability
(2008-04-25) Doig, Sean; Toddi Steelman, Committee Co-Chair; Robert Abt, Committee Co-Chair; James Gregory, Committee Member
Using GIS and LIDAR to Map Headwaters Stream Networks in the Piedmont Ecoregion of North Carolina
(2005-03-03) Garcia, Valerie Cover; James Gregory, Committee Member; George Hess, Committee Member; Heather Cheshire, Committee Chair
A large percentage of nonpoint source pollution found in our Nation's waterbodies is suspected to occur through first- and second-order (headwaters) streams. Such streams drain a much greater proportion of watershed area and have a much greater length of riparian zone interaction with the land than the higher-order streams typically studied for nonpoint source water quality problems. The State of North Carolina and the U.S. EPA are interested in examining the contribution of lowerorder streams to the overall nonpoint source pollution problem; however, the mapping of first- and second-order streams is extremely poor. The recent availability of fine resolution Light Detection and Ranging (LIDAR) data for portions of the State of North Carolina provides the opportunity for developing improved methods of mapping lower-order streams using Geographic Information System (GIS) approaches. In this study, I investigated the state-of-science for mapping topography and extracting headwaters stream networks using LIDAR data and GIS approaches. I applied these techniques to map headwaters streams at a study site in the Piedmont Ecoregion of North Carolina. I found that LIDAR produced more accurate elevation maps (elevation accuracy within 1.2') than currently available maps, such as the USGS 7.5 minute Digital Elevation Models (elevation accuracy within 49'). The Triangulated Irregular Network (TIN) produced the best topographic maps, but the Digital Elevation Model (DEM) was better for automatically extracting headwaters streams. The best headwaters stream maps were derived by using a hydro-enforced TIN for generating the base DEM,and extracting the stream network from this base DEM using ArcHydro and the AGREE algorithm. These improved headwaters stream maps will enable decision-makers to assess and mitigate nonpoint source water quality problems.
What Factors Influence Freshwater Molluscan Survival in the Conasauga River?
(2005-06-28) Sharpe, Adam James; Elizabeth G. Nichols, Committee Chair; James Gregory, Committee Member; Chris Hofelt, Committee Member
Recent biological inventory data shows a consistent decline in molluscan abundance and biodiversity in the Conasauga River Basin in Northwest GA. This study was initiated to monitor sediment and water quality by stable nitrogen isotope ratio analyses (IRMS) of snails and sediments, permeable membrane devices (PMD), polar organic chemical integrative samplers (POCISTM), and conventional water quality analyses for the Conasauga River Basin. Atrazine, metalochlor, prometon, and simazine were the most frequently detected herbicides throughout the basin. Most of the ambient concentrations of detected organic contaminants are at or near the method detection limit and all are well below any aquatic life criteria. Recent evaluation of water quality criteria for ammonia and nitrate suggest that these criteria levels are not protective for mussels. Data suggests that a shift to livestock and row crop land-use results in greater water nutrient levels and increased δ15N signatures for aquatic snails. Mean δ15N values for snails collected at national forest sites are significantly different from δ15N in snails collected in agricultural areas of the Conasauga River Basin (Student t-test, p<0.05). δ15N signatures of cow manure (6.71‰ wet, 8.40‰ dry) and poultry manure treated soil (9.47?) were similar to those of the snails collected in the agricultural areas of the Conasauga. Dissolved nitrate had elevated δ15N signatures that reflected the upper range of δ15N signatures for the aquatic snails. Elevated nitrogen isotope signatures indicate the fact that a shift in land use within in the basin is impacting the dominant nitrogen source to the aquatic environment. Continued evaluation of water quality criteria levels are needed to determine if aquatic habitats are viable for mussel reproduction, growth, and survival.