Legacy sediment storage in New England river valleys: Anthropogenic processes in a postglacial landscape

Johnson, Kaitlin M.; Snyder, Noah P.; Castle, S.; Hopkins, A. J.; Waltner, Mason; Merritts, Dorothy J.; Walter, Robert C.

doi:10.1016/j.geomorph.2018.11.017

Cited by 26 publications

(24 citation statements)

References 30 publications

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“…Many of these Group 2 dams have been built atop natural bedrock knickpoints, with limited sediment storage as evidenced by cobble or bedrock channels upstream of the dam. Dated millpond sediments from three watersheds across the glaciated Northeast US found that many of these dams, which are small relative to their watershed areas, filled with sediment rapidly after they were constructed (Johnson et al 2019).…”

Section: Geophysical Measurementsmentioning

confidence: 99%

Watershed Suspended Sediment Supply and Potential Impacts of Dam Removals for an Estuary

Ralston

Yellen

Woodruff

2021

Estuaries and Coasts

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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.

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Section: Geophysical Measurementsmentioning

confidence: 99%

Watershed Suspended Sediment Supply and Potential Impacts of Dam Removals for an Estuary

Ralston

Yellen

Woodruff

2021

Estuaries and Coasts

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“…Legacy sediments were then referred to as "modern sediment" or "post-settlement alluvium" (Happ et al, 1940, Knox, 1972Dearman and James, 2019). Multiple examples of such deposits were described in the USA, mostly in the Mid-Atlantic region (Walter and Merritts, 2008;Merritts et al, 2011;Hupp et al, 2013;Donovan et al, 2015, Johnson et al, 2018. As a result, both their characteristics and their formation mechanism are well-documented.…”

Section: Europe: a Comparison In The Anthropocene Periodmentioning

confidence: 99%

“…As a result, both their characteristics and their formation mechanism are well-documented. Legacy sediments in the USA are typically recognizable as an important accumulation of fine sediments (up to m high) on both sides of rivers, forming floodplain levels, even terraces that are mostly disconnected from the main channel (Walter et Merritts, 2008;Webb-Sullivan et Evans, 2014;Johnson et al, 2018). There is a consensus that such deposits were formed following European settlement in the 17 th century: the subsequent development of intensive agricultural practices led to accelerated upland erosion, generating an unnaturally large amount of sediments that settled in valleys and caused the watercourses to aggrade.…”

Section: Europe: a Comparison In The Anthropocene Periodmentioning

confidence: 99%

“…That is not the case of the infrastructure-induced LS on the Rhône River that form a relatively thin layer (up to 1 m observed in Vauclin et al, 2019 and up to 2.5 m according to Tena et al, 2020) that does not always stand out in comparison to the channel level. Regarding sedimentological characteristics, besides important sedimentation rates, American LS can sometimes also be distinguished from earlier alluvium by lower organic carbon contents (Weitzman et al, 2014;Johnson et al, 2018;Dearman and James, 2019), lower bulk density and lower stratification (Dearman and James, 2019). The grain-size, however, can be similar in both sediment units (Dearman and James, 2019) and therefore cannot be used as a discerning criterion.…”

Section: A Conceptual Comparison Between Synchronous Legacy Sedimentamentioning

confidence: 99%

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Legacy sediments in a European context: The example of infrastructure-induced sediments on the Rhône River

et al. 2020

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The concept of legacy sediments (LS) as sediments periodically produced by anthropogenic disturbances has been introduced in the early 2010s and has been increasingly used since then, primarily in the USA. It is a key concept to characterize river corridors health and design relevant restoration schemes. Surprisingly, examples of legacy sediments in European rivers remain scarce in the literature, despite the long history of human influences in this part of the world. In this viewpoint paper, we argue that while land-use changes within upstream basins seem to be mostly responsible for legacy sedimentation along downstream river sections in New World countries like the USA or Australia, reach-scale engineering is the main driver of legacy sedimentation along large Alpine European rivers during the Anthropocene era. We give an example of LS induced by navigation infrastructures (groynes and lateral training walls) present along the Rhône River downstream of Lyon (France), and assume that analogous LS might exist in most engineered rivers. Those infrastructure-induced sediments differ from the classic examples of American LS in terms of formation mechanisms and characteristics, which leads us to suggest a broadened definition of legacy sediments in order to make the concept more applicable to the European context.

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“…In fact, some sediment in paraglacial landscapes may never reach a large river because of natural sediment trapping in ponds and on lowrelief coastal plains (Kasprak et al 2013). Additionally, in New England and other areas with European-style agriculture, sediment may accumulate behind mill dams and on the upslope side of stone walls built by early Colonial farmers (Walter and Merritts 2008;Johnson and Ouimet 2016;Johnson et al 2018), further preventing sediment from reaching the coast.…”

Section: Distal Human and Natural Influences On Estuarine Sediment Acmentioning

confidence: 99%

Tidal erosion and upstream sediment trapping modulate records of land-use change in a formerly glaciated New England estuary

Shawler

Hein

Canuel

et al. 2019

Anthropocene Coasts

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Land clearing, river impoundments, and other human modifications to the upland landscape and within estuarine systems can drive coastal change at local to regional scales. However, as compared with mid-latitude coasts, the impacts of human modifications along sediment-starved formerly glaciated coastal landscapes are relatively understudied. To address this gap, we present a late-Holocene record of changing sediment accumulation rates and sediment sources from sediment cores collected across a tidal flat in the Merrimack River estuary (Mass., USA). We pair sedimentology, geochronology, bulk- and stable-isotope organic geochemistry, and hydrodynamic simulations with historical data to evaluate human and natural impacts on coastal sediment fluxes. During the 17th to 19th centuries, accumulation rates increased by an order of magnitude in the central tidal flat, likely in response to enhanced delivery of terrestrial sediment resulting from upland deforestation. However, the overall increase in accumulation (0.56–2.6 mm/year) within the estuary is subtle and spatially variable across the tidal flats because of coincident anthropogenic land clearing and dam building, upland sediment storage, and estuarine hydrodynamics. This study provides insight into the response of formerly glaciated fluvial-coastal systems to human modifications, and underscores the role of estuarine environmental conditions in modifying upland signals of land-use change.

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Legacy sediment storage in New England river valleys: Anthropogenic processes in a postglacial landscape

Cited by 26 publications

References 30 publications

Watershed Suspended Sediment Supply and Potential Impacts of Dam Removals for an Estuary

Watershed Suspended Sediment Supply and Potential Impacts of Dam Removals for an Estuary

Legacy sediments in a European context: The example of infrastructure-induced sediments on the Rhône River

Tidal erosion and upstream sediment trapping modulate records of land-use change in a formerly glaciated New England estuary

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