Retention of alluvial sediment in the tidal delta of a river draining a small, mountainous coastal watershed

Watson, E. B.; Gray, Andrew B.; Pasternack, G. B.; Woolfolk, Andrea

doi:10.1016/j.csr.2019.05.015

Cited by 3 publications

(3 citation statements)

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“…A frequent premise of coastal research (22,38) and a message in the popular science press (39) is that dams have reduced river sediment loads to the US coast and jeopardized tidal wetlands dependent on that river sediment. In reality, dam removal can enhance coastal sedi-ment (40) and restore sediment conveyance across high gradient coastlines (11,41). Yet the effect of dams on a broader size range of rivers (most dams occur on small, not large rivers: (42) and resulting trends in coastal sediment delivery over time and space are not consistently negative (43)(44)(45)(46).…”

Section: Discussionmentioning

confidence: 99%

“…This paucity of river sediment data and the bias of disciplinary discourse focusing on large rivers has, not unexpectedly, swayed studies on estuaries and tidal wetlands to frame hypotheses based on the patterns observed for large rivers and their tidal wetland deltas. Given that smaller rivers exponentially outnumber large rivers at the coast ( 9 ) and provide a large cumulative sediment load on active margins ( 10 , 11 ), a coast-wide accounting of all rivers’ sediment fluxes and associated tidal wetland elevation change is needed to recenter expectations for the role rivers play in delivering sediment to tidal wetlands.…”

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Watershed sediment cannot offset sea level rise in most US tidal wetlands

Ensign,

Halls,

Peck

2023

Science

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Watershed sediment can increase elevation of tidal wetlands struggling against rising seas, but where and how much watershed sediment helps is unknown. By combining contiguous US datasets on sediment loads and tidal wetland areas for 4972 rivers and their estuaries, we calculated that river sediment accretion will be insufficient to match sea level rise in 72% of cases because most watersheds are too small (median 21 square kilometers) to generate adequate sediment. Nearly half the tidal wetlands would require 10 times more river sediment to match sea level, a magnitude not generally achievable by dam removal in some regions. The realization that watershed sediment has little effect on most tidal wetland elevations shifts research priorities toward biological processes and coastal sediment dynamics that most influence elevation change.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Watershed sediment cannot offset sea level rise in most US tidal wetlands

Ensign,

Halls,

Peck

2023

Science

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“…During the early 20 th century, sedimentation near the inlet was caused by erosion of cleared land in the watershed and diking of large parts of the adjacent, interconnected estuary, which decreased the tidal prism. However, construction of a marine inlet for a deepwater harbor in 1946 then dramatically increased tidal exchange to the Slough (Watson et al, 2019;Woolfolk, unpublished data).…”

Section: Study Sitementioning

confidence: 99%

Use of historical isoscapes to develop an estuarine nutrient baseline

Champlin,

Woolfolk,

Oczkowski

et al. 2023

Front. Mar. Sci.

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Coastal eutrophication is a prevalent threat to the healthy functioning of ecosystems globally. While degraded water quality can be detected by monitoring oxygen, nutrient concentrations, and algal abundance, establishing regulatory guidelines is complicated by a lack of baseline data (e.g., pre-Anthropocene). We use historical carbon and nitrogen isoscapes over ~300 years from sediment cores to reconstruct spatial and temporal changes in nutrient dynamics for a central California estuary, Elkhorn Slough, where development and agriculture dramatically enhanced nutrient inputs over the past century. We found strong contrasts between current sediment stable isotopes and those from the recent past, demonstrating shifts exceeding those in previously studied eutrophic estuaries and substantial increases in nutrient inputs. Comparisons of contemporary with historical isoscapes also revealed that nitrogen sources shifted from a historical marine-terrestrial gradient with higher δ15N near the inlet to amplified denitrification at the head and mouth of the modern estuary driven by increased N inputs. Geospatial analysis of historical data suggests that an increase in fertilizer application – rather than population growth or increases in the extent of cultivated land – is chiefly responsible for increasing nutrient loads during the 20th century. This study demonstrates the ability of isotopic and stoichiometric maps to provide important perspectives on long-term shifts and spatial patterns of nutrients that can be used to improve management of nutrient pollution.

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Anthropogenic impact on the organic carbon sources, transport and distribution in a subtropical semi-enclosed bay

Gao

Chen

et al. 2021

Science of The Total Environment

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Retention of alluvial sediment in the tidal delta of a river draining a small, mountainous coastal watershed

Cited by 3 publications

References 50 publications

Watershed sediment cannot offset sea level rise in most US tidal wetlands

Watershed sediment cannot offset sea level rise in most US tidal wetlands

Use of historical isoscapes to develop an estuarine nutrient baseline

Anthropogenic impact on the organic carbon sources, transport and distribution in a subtropical semi-enclosed bay

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