HR: 0800h
AN: H41D-0768    [Abstracts]
TI: Measuring the Erosion of River Channel Widths Impacted by Watershed Urbanization Using Historic Aerial Photographs and Modern Surveys
AU: * Galster, J C
EM: galsterj@mail.montclair.edu
AF: Department of Earth and Environmental Studies Montclair St. University, 1 Normal Ave. Mallory Hall, Room 252, Montclair, NJ 07043, United States
AU: Pazzaglia, F J
EM: fjp3@lehigh.edu
AF: Department of Earth and Environmental Science Lehigh University, 31 Williams Dr., Bethlehem, PA 18015, United States
AU: Germanoski, D
EM: germanod@lafayette.edu
AF: Department of Geology and Environmental Geosciences Lafayette College, Van Wickle Hall, Easton, PA 18042, United States
AB: Land use in a watershed exerts a strong influence on trunk channel form and process. Land use changes act over human time scales which is short enough to measure their effects directly using historic aerial photographs. We show that high-resolution topographic surveys comparing channel form for paired watersheds in the Lehigh Valley, PA are indistinguishable, but have channel widths that have changed dramatically in the past five decades. The two watersheds, Little Lehigh Creek and Sacony Creek, are similar in all respects except they have different amount of urban land use. Aerial photographs of the urbanized Little Lehigh Creek show that a majority of the measured widths (67 of 85) were statistically wider in 1999 than in 1947. In contrast, the measured widths from the agricultural Sacony Creek are more evenly distributed among those that widened (18), narrowed (28), and those that were statistically unchanged (6) from 1946 to 1999. From 1946 to 1999 the only section of Sacony creek that widened was that reach downstream of the only sizable urban area in the watershed. The current land use in Sacony Creek watershed resembles that of 1946, while the Little Lehigh Creek watershed has more than tripled its urban area. These data suggest that the increase in urban areas that subsequently increases peak discharges is the mechanism behind the widening that occurred in the Little Lehigh Creek. These wider channels can affect water quality, aquatic habitat, suspended sediment loads, and river aesthetics.
DE: 1815 Erosion
DE: 1819 Geographic Information Systems (GIS)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1856 River channels (0483, 0744)
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2007 Fall Meeting