What are Key Conditions for Marsh Survival Amid Rising Seas?
USGS Scientists Use 3D Modeling to Understand Sediment Dynamics in Coastal Marshes
As sea levels continue to rise, coastal marshes face increasing risk of inundation and erosion. These wetlands rely on a steady supply of sediment to keep up with rising waters, but the suite of conditions that control sediment accumulation are difficult to predict.
A new study led by USGS scientists uses advanced 3D modeling to identify the key factors that determine whether a marsh gains or loses sediment—findings that could improve efforts to protect these vital ecosystems.
How Marshes Keep Up with Sea-Level Rise
For a marsh to keep pace with sea-level rise, it must build up enough sediment via accretion to counteract erosion. This sediment can come from nearby rivers, bays, and mudflats, but the process of sediment transport is complex and often poorly understood. In the study, researchers used on-the-ground observations from China Camp Marsh in San Francisco Bay to create a numerical model incorporating flow, waves, vegetation, and sediment movement in order to better understand which conditions help or hinder marsh survival.
Their analysis found that marshes accumulate sediment the fastest when two of the following occur simultaneously:
Large waves stir sediment higher into the water column.
Loose, easily eroded sediment is available on the seafloor.
Slow sediment settling allows more particles to drift into marsh areas before sinking.
By simulating these interactions, researchers were able to fine-tune their model parameters and improve predictions about sediment accretion, and thus marsh resilience.
Why It Matters
Coastal marshes provide critical habitat for fish and wildlife, buffer shorelines from storm surges, and help store carbon, making their survival essential in the face of climate change. This study highlights the importance of adjacent mudflats in delivering sediment to marshes, and underscores how small variations in wave activity and sediment behavior can play an outsized role in marsh resilience.
By improving how models capture these dynamics, scientists can better predict how marshes will respond to sea-level rise and identify strategies for their protection. These findings could help guide future restoration efforts and inform coastal management policies.
Read the study, Sensitivity Analysis of a Dynamic Vegetation-Sediment Transport Model Using Equadratures: Exploring Inorganic Accretion on a Marsh Platform, in the Journal of Geophysical Research: Earth Surface.
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