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Channel geomorphic evolution after dam removal; is scale important?


Post-dam removal geomorphologic adjustment of a stream channel has been documented in the scientific literature at watershed, hillslope and laboratory scales. Hillslope scale studies in channel-cross-sections are most common, and add significant value in the dam-removal literature. This study examines geomorphic stream channel adjustment following dam removal at the hillslope scale under natural climatic conditions. A sediment-filled silt fence dam (1 m tall, 12.65 m wide) was removed in three stages and the width and depth of the upstream developing channel was monitored at six transects for fifteen months. Headcut retreat and changes in channel sinuosity were also recorded. After the silt fence dam was removed, channel development was initiated by headcut formation which migrated upstream at a rate of 4 cm/day for about ten months and then gradually reached attenuation. The channel progressed through four distinct stages: Stage 1 [Initial conditions]; Stage 2 [Downcutting] -wide, shallow, meandering channel incised to a maximum depth of 0.52 m, and sinuosity decreased; Stage 3 [Floodplain development] -upon reaching base level, surface runoff began to meander within the channel, widening it through bank slumps and erosion; Stage 4 [Quasi-equilibrium] -channel development reached dynamic (quasi) equilibrium with only minor widening at downstream transects [maximum width of the incised channel reached 0.46 m] accompanied by sediment aggradation. The stages of upstream channel development and headcut retreat pattern in this study are consistent with other studies at the laboratory and watershed scales indicating that channel development after dam removal is scale independent.

ISSN: 1078-7275
EISSN: 1558-9161
Coden: ENGEA9
Serial Title: Environmental & Engineering Geoscience
Serial Volume: 23
Serial Issue: 3
Title: Channel geomorphic evolution after dam removal; is scale important?
Affiliation: East Tennessee State University, Department of Geosciences, Johnson City, TN, United States
Pages: 209-220
Published: 20170125
Text Language: English
Publisher: Geological Society of America, Association of Engineering Geologists, College Station, TX, United States
References: 54
Accession Number: 2017-034838
Categories: GeomorphologyEnvironmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
N35°00'00" - N36°45'00", W90°15'00" - W81°40'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Association of Engineering Geologists and the Geological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201720
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