Details:

Journal Title:
Earth Surface Processes and Landforms
Personal Author:
Cashman, Matthew J. ; Gellis, Allen C. ; Boyd, Eric ; Collins, Mathias J. ; Anderson, Scott W. ; ... More +
Cashman, Matthew J. ; Gellis, Allen C. ; Boyd, Eric ; Collins, Mathias J. ; Anderson, Scott W. ; McFarland, Brett D. ; Ryan, Ashley M. Less -
NOAA Program & Office:
NMFS (National Marine Fisheries Service)
Description:
In this study, we captured how a river channel responds to a sediment pulse originating from a dam removal using multiple lines of evidence derived from streamflow gages along the Patapsco River, Maryland, USA. Gages captured characteristics of the sediment pulse, including travel times of its leading edge (~7.8 km yr−1) and peak (~2.6 km yr−1) and suggest both translation and increasing dispersion. The pulse also changed local hydraulics and energy conditions, increasing flow velocities and Froude number, due to bed fining, homogenization and/or slope adjustment. Immediately downstream of the dam, recovery to pre-pulse conditions occurred within the year, but farther downstream recovery was slower, with the tail of the sediment pulse working through the lower river by the end of the study 7 years later. The patterns and timing of channel change associated with the sediment pulse were not driven by large flow or suspended sediment-transporting events, with change mostly occurring during lower flows. This suggests pulse mobility was controlled by process-factors largely independent of high flow. In contrast, persistent changes occurred to out-of-channel flooding dynamics. Stage associated with flooding increased during the arrival of the sediment pulse, 1 to 2 years after dam removal, suggesting persistent sediment deposition at the channel margins and nearby floodplain. This resulted in National Weather Service-indicated flood stages being attained by 3–43% smaller discharges compared to earlier in the study period. This study captured a two-signal response from the sediment pulse: (1) short- to medium-term (weeks to months) translation and dispersion within the channel, resulting in aggradation and recovery of bed elevations and changing local hydraulics; and (2) dispersion and persistent longer-term (years) effects of sediment deposition on overbank surfaces. This study further demonstrated the utility of US Geological Survey gage data to quantify geomorphic change, increase temporal resolution, and provide insights into trajectories of change over varying spatial and temporal scales.
Keywords:
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Dam Retirement Sediments (Geology) Aggradation Channel Evolution Dam Removal Deposition Dispersion Sediment Pulse Sediment Wave Specific Stage Translation
Source:
arth Surf. Process. Landforms. 2021; 46: 1145– 1159.
DOI:
https://doi.org/10.1002/esp.5083
Document Type:
Journal Article
Place as Subject:
Patapsco River (Md.)
Rights Information:
Public Domain
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:d25f7bad0c83451693dc3c8a787fe9147c8ac8fb364b3d1d05d5182d53f9b20a
Download URL:
https://repository.library.noaa.gov/view/noaa/29311/noaa_29311_DS1.pdf
File Type:

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