HR: 1340h
AN: H13E-1365    [Abstracts]
TI: Flow resistance from self formed step pool bedforms
AU: * Curran, J C
EM: jc49@txstate.edu
AF: Texas State University, Dept. of Geography 601 University Drive, San Marcos, TX 78666 United States
AB: Step pool bedforms are commonlz found in steep channels, where they increase the local channel roughness through the formation of tumbling jet flows over step crests into pools. Recognition of the abilitz of step pool sequences to increase channel roughness and thus dissipate flow energy has led to an increased use of step pools in stream restoration efforts. Steps are created wherever a disconnect is observed in the vertical profile of a river. Such disconnects often occur in highly eroded channels, locally increasing the channel slope. These channels have degraded in response to an increase in the flow volume input and the competance of the channel to transport sediment. Streams in areas of suburban developments provide an example of a situation where step pools are constructed in an effort to stabilize the channel bed. When constructing step sequences, the question remains of what spacing to use when setting step locations. Traditionally steps have been constructed with equal spacing, resembling a staircase in the channel. This is in an effort to maximize the flow resistance and energy dissipation due to the steps. However, natural steps have been shown to follow a modified Poisson distribution, where steps are equally likely to have any spacing beyond a specified minimum. A step configuration closer to the spacing measured in freely set steps may provide a more stable bedform for restoration projects. Steps were created in a series of flume experiments during which the steps were free to establish spacing. The flow resistance created by these steps is different from that produced by equally spaced step sequences. This research analyzes the resistance from the freely deposited steps and compares it to what has been measured from equally spaced steps.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1834 Human impacts
DE: 1862 Sediment transport (4558)
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: Fall Meeting 2005