Glaciation has been one of the most significant geologic process to shape the landscape in much of the northern United States. Glaciers have repeatedly covered Illinois throughout the Pleistocene epoch (approximately 2,000,000 to 8,000 years ago). The erosion and deposition of sediment by glaciers has changed the landscape in Illinois by filling pre-glacial river valleys, changing the course of rivers, and by creating new landforms. Some of the most prominent landforms created by glacial deposition in Illinois are end moraines. End moraines are broad, low-relief ridges which mark the glacial ice-margin advance and readvance positions. The morphology of the moraines is highly variable and can be dependent on the length of time the glacial ice occupied a given position on the landscape, the amount of sediment carried by the glacier, and age of the moraine. Readily available surface elevation data (United States Geological Survey Digital Elevation Model data) combined with the analytical tools provided by the ArcInfo software helps geologists to visualize, analyze, and model the landscape. Functions within GRID, TIN, ARC, and ARCPLOT were used to characterize differences within moraine forms. Cross sections, slope analysis, and volumetrics were used to identify differences between previously mapped glacial moraines, and to locate previously unidentified features on the landscape that may be mapped as moraines.
Union Pacific Resources Company (UPR) is an independent domestic Oil and Gas Company that owns or manages in excess of 35,000 leases and contracts which cover approximately ten million acres throughout North America. Historically, UPR has managed its Land and Lease information in mainframe based textual databases while related spatial data has been captured separately as hand drafted and/or CAD maps. UPR and Amoco Corporation (Amoco), an integrated international Oil and Gas company who has experienced many of the same challenges, have formed a partnership with Eagle Information Mapping, Inc. and Innovative Business Solution, Inc. to re-engineer a desktop GIS solution for Land/Lease management. This paper will describe the ArcView-based ViewPoint-Land system including the basis for the design, an overview of hardware and software specifications and the system functionality. A case study will be presented to illustrate process improvement and functionality of the new system.
Physical habitat characteristics influence the structure and composition of biological communities. Habitat features of two reaches of the middle Platte River in central Nebraska were surveyed four times during 1993-1995. Measurements included channel cross-section profiles, longitudinal water-surface profiles, and planimetry of targeted in-stream habitat features. Biological communities also were sampled, twice in one reach and three times in the other. Survey data were converted to geospatial data sets using commercial GIS software. Spatial analyses were performed to derive parameters such as channel width, bank angle, stream-centerline stationing, and total shoreline length. Products include detailed maps of reach planimetry and channel cross-sectional graphs showing interannual variability in habitat conditions from 1993 to 1995. Natural creation and destruction of specific habitat types were documented. Channel features migrated both laterally and downstream. Most of the long-term change in stream habitat features occurs during the short periods when flow is near bankfull. Unusually high streamflows in 1995 provided an opportunity to estimate longer-term variability for some physical habitat characteristics.
The U.S. Geological Survey is studying channel stability of the Lower Virgin River from 1938 to the present. Aerial photography at scales ranging from 1:6000 to 1:66,000 and satellite imagery are being analyzed to determine quantitative changes in channel morphology using digital methods. For a 30-mile stretch of the river, eight separate reaches, each about 1 to 1.5 miles long, are being processed. Aerial photography from a combination of 29 dates and sources are optically scanned and registered to a standard coordinate system, using control points and image-processing techniques. Channel boundaries, sand bars, and the thalweg -- the deepest part of the channel -- are delineated onto prints of the registered images and then digitized into ArcInfo coverages. The coverages are checked for accuracy of locational coordinates and feature coding. These delineations are used as the base for further digital processing. All digital image processing is done using a combination of ArcInfo and FORTRAN programs. The entire process is controlled through an interactive menu, designed for rapid sequential processing of a large number of images for each reach. To begin processing, the overall reach orientation, or linear direction of the river within that reach, is delineated. That orientation is used in subsequent processing of each of the available images for that reach. Next, based on the feature coding, the area of the sand bars and the area of the channel are calculated for each image. The thalweg sinuosity and the maximum width of the channel meander belt, perpendicular to the reach orientation, are calculated. In addition, the reach is subdivided into a series of equal-width segments along the reach-orientation line. For each segment, lines are constructed that are perpendicular to the average orientation of the outer channel boundaries within that segment. These lines are used to calculate the width of the channel at the center of each segment. All of these statistics are tabled for further geomorphic comparison and interpretation. The digitized channel-area features for two selected images can be overlaid for planimetric analysis, showing changes from one date to another, including areas of scour and fill. Also, an overlay of all images for a reach provides an indication of channel stability over time. Regions with high frequency of occurrence represent greater channel stability. Stability maps and statistics are created both for thalwegs and channel-area features by overlaying the images and applying weighting factors based on the period of time each image represents. By using digital methods, a large data set can be processed and analyzed quickly and easily. These results can then be used to document channel changes through time and to help understand the processes of geomorphic change.