Publication Date:
2022-05-26
Description:
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ralston, D. K., Yellen, B., & Woodruff, J. D. Watershed suspended sediment supply and potential impacts of dam removals for an estuary. Estuaries and Coasts, (2021), https://doi.org/10.1007/s12237-020-00873-3.
Description:
Observations and modeling are used to assess potential impacts of sediment releases due to dam removals on the Hudson River estuary. Watershed sediment loads are calculated based on sediment-discharge rating curves for gauges covering 80% of the watershed area. The annual average sediment load to the estuary is 1.2 Mt, of which about 0.6 Mt comes from side tributaries. Sediment yield varies inversely with watershed area, with regional trends that are consistent with substrate erodibility. Geophysical and sedimentological surveys in seven subwatersheds of the Lower Hudson were conducted to estimate the mass and composition of sediment trapped behind dams. Impoundments were classified as (1) active sediment traps, (2) run-of-river sites not actively trapping sediment, and (3) dammed natural lakes and spring-fed ponds. Based on this categorization and impoundment attributes from a dam inventory database, the total mass of impounded sediment in the Lower Hudson watershed is estimated as 4.9 ± 1.9 Mt. This represents about 4 years of annual watershed supply, which is small compared with some individual dam removals and is not practically available given current dam removal rates. More than half of dams impound drainage areas less than 1 km2, and play little role in downstream sediment supply. In modeling of a simulated dam removal, suspended sediment in the estuary increases modestly near the source during discharge events, but otherwise effects on suspended sediment are minimal. Fine-grained sediment deposits broadly along the estuary and coarser sediment deposits near the source, with transport distance inversely related to settling velocity.
Description:
This work was sponsored by the National Estuarine Research Reserve System Science Collaborative, which is funded by the National Oceanic and Atmospheric Administration and managed by the University of Michigan Water Center (NAI4NOS4190145). Additional support for participating graduate and undergraduates was provided by the Northeast Climate and Adaptation Center and the Hudson River Fund. Additional support for DKR was provided by the Hudson River Foundation (Grant No. 003/19A). Data from sediment cores that were collected in association with this manuscript are archived here: https://doi.org/10.7275/dh3v-0x33.
Keywords:
Dam removal
;
Suspended sediment
;
Watershed sediment yield
;
Sediment supply
;
Sediment trapping
Repository Name:
Woods Hole Open Access Server
Type:
Article
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