| Two new watershed-delineation approaches are used to build statistical regression models that explain the variations in Qualitative Habitat Evaluation Index (QHEI) scores at hundreds of sites in the Eastern Corn Belt Plains ecoregion of Ohio. Hydrologically contributing areas upstream of the sampling stations are delineated using (1) non-overlapping watersheds up to the next upstream sampling station, and (2) custom watershed areas, called localsheds , delineated only up to a user-specified upstream flow-length. Both approaches provide an insight into the scale effects of various stressors. A large GIS-intensive database is developed with fine-resolution data on 30 m DEM, 1:24,000 scale roads and streams with network topology, proportionally allocated census block demography, and 30m land cover characteristics. Stream order, reach sinuosity, and upstream network distances are derived. The models explain about 40% of the variation in habitat quality using stressor-related data within hydrologically connected areas that are only a mile upstream of the sampling sites. The results confirm the utility of the localshed framework and suggest that riparian row crops, commercial, and urban land uses in narrow strips, relatively broad swaths of deciduous forest, stream channelization, reach sinuosity, and stream order have a significant impact on the habitat immediately downstream of stress locations. Further research is outlined for model structure, data resources, and GIS software. |
