Stream channel incision of the Bluff’s Parcel Tributary, Delaware: sediment production caused by recent land use changes in Delaware’s coastal plain

Date
2012
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University of Delaware
Abstract
This study illustrates the use of dendrogeomorphic analyses of tree roots for determining time-averaged, channel incision rates at the Bluff’s Parcel Tributary, a Strahler second order stream located in the Coastal Plain of Delaware. A combination of both macroscopic and microscopic analysis of the cellular structure of roots from three trees are used to determine the year of exposure (i.e., the onset of erosion) and subsequent rates of incision in the channel. Results indicate that incision rates vary from 0.019 m yr^-1 to 0.022 m yr^-1 and suggest that the channel has been incising for approximately 50 years. The volume of sediment removed during this period is approximately 744 m^3, or an average of 14.9 m^3 yr^-1 of sediment delivered to Blackbird Creek since the onset of erosion. Analysis of land use land cover change observed in aerial photographs from A.D. 1937 to A.D. 1992 indicates a coincidence of increased urbanization in the watershed at the onset of incision. The results illustrate how minor amounts of urbanization in the uplands of a watershed can have significant impacts on small streams. Given the density of similarly sized tributaries undergoing an analogous channel response throughout the Blackbird Creek watershed, the sediment load contribution of these incising tributaries has the potential to negatively impact ecologically sensitive estuarine tidal environments.
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