HR: 08:30h
AN: NB31C-01 INVITED     [Abstracts]
TI: Restoration of Sinuous Channels with Pool Riffle Morphology in Floodplains Impacted by Mill Dams
AU: * Oberholtzer, W
EM: Ward@Landstudies.com
AF: LandStudies, Inc., 315 North Street , Lititz, PA 17543
AB: The association of fine-grained alluvial sediments with agricultural period land-use in the Piedmont of the mid-Atlantic United States is well documented; however, the impact of small dams, primarily for mills has not been considered fully. Research of historic documents has revealed over 500 mills and associated dams in Lancaster County, Pennsylvania, directly impacting 300 km of valley. Examination of historic sediments indicated fine-grain sediment deposits up to 5.8 m. Although many dams have been partially or completely breached, the legacy effects of these structures persist and, in some cases, control channel grade. The high frequency of small dams on some streams has severely altered the interaction of the floodplain and channel, channel dimensions and transport characteristics, bed and valley profiles, bed substrate, and bank materials. Channel response to contemporary land-use can be highly affected by the legacy effects. Stream assessments and restoration designs should consider the important legacy effects of past mill operations. In design of stream restorations, several questions arise about dominant discharge, bank heights, local base level control, floodplain levels, potential excavation requirements and potential long-term channel lateral and vertical responses. These questions have been addressed in several stream restoration projects completed by the author.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
DE: 1821 Floods
DE: 1824 Geomorphology (1625)
DE: 1829 Groundwater hydrology
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly