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<p>Studies of sedimentation in low-elevation coastal zones often focus on long-term average sediment accumulation rates. Although decadal and centennial sedimentation rates are key to understanding resilience to relative sea-level rise, they overlook short-term (often seasonal or shorter) fluctuations that complicate impacts on ecosystems. Using a combination of field observations and hydrodynamic model results, we examined event- to seasonal-scale sediment dynamics and deposition rates in the Coos estuary, Oregon, a small, strongly forced system representative of estuaries along the U.S. Pacific Northwest coast. During rainfall events, peaks in turbidity are followed by up to 3&#xa0;cm of mud deposition on tidal flats in the middle and upper estuary. Meanwhile, little or no deposition (0–1&#xa0;cm) occurs in the lower estuary. The spatial pattern of sedimentation on tidal flats is consistent across timescales (event to centennial) but is inconsistent with sedimentation patterns in higher-elevation marshes. Whereas deposition on tidal flats in the middle and upper estuary occurs 2–3 times faster than deposition in the lower estuary, deposition in marshes appears to be slowest in the middle estuary. After a storm, the sediment deposited on tidal flats in the middle and upper estuary is reworked on the scale of weeks to a month and thus is not preserved in the long-term record. Projected climate-driven increases in the frequency and intensity of rainstorms will likely increase event-driven peaks in turbidity, bed stress, and sediment deposition, heightening the importance of short-term events as drivers of long-term estuary change from both ecological and sedimentological perspectives.</p>

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Estuarine Sediment Dynamics and the Importance of Storms in Moving (and Removing) Mud

  • 期刊论文

  • 发表日期：

    2025年4月25日

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  • Molly E. Keogh,
  • David A. Sutherland,
  • Emily F. Eidam,
  • Tyler D. Souza,
  • Jenni Schmitt,
  • Alicia Helms,
  • David K. Ralston

摘要

Studies of sedimentation in low-elevation coastal zones often focus on long-term average sediment accumulation rates. Although decadal and centennial sedimentation rates are key to understanding resilience to relative sea-level rise, they overlook short-term (often seasonal or shorter) fluctuations that complicate impacts on ecosystems. Using a combination of field observations and hydrodynamic model results, we examined event- to seasonal-scale sediment dynamics and deposition rates in the Coos estuary, Oregon, a small, strongly forced system representative of estuaries along the U.S. Pacific Northwest coast. During rainfall events, peaks in turbidity are followed by up to 3 cm of mud deposition on tidal flats in the middle and upper estuary. Meanwhile, little or no deposition (0–1 cm) occurs in the lower estuary. The spatial pattern of sedimentation on tidal flats is consistent across timescales (event to centennial) but is inconsistent with sedimentation patterns in higher-elevation marshes. Whereas deposition on tidal flats in the middle and upper estuary occurs 2–3 times faster than deposition in the lower estuary, deposition in marshes appears to be slowest in the middle estuary. After a storm, the sediment deposited on tidal flats in the middle and upper estuary is reworked on the scale of weeks to a month and thus is not preserved in the long-term record. Projected climate-driven increases in the frequency and intensity of rainstorms will likely increase event-driven peaks in turbidity, bed stress, and sediment deposition, heightening the importance of short-term events as drivers of long-term estuary change from both ecological and sedimentological perspectives.