267-13 Channeling the Past: Restoring Healthy Hydrology in Historically Farmed Salt Marshes throughout New England

Session: Advances in Fluvial Processes and Sediment Transport (Posters)

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Abstract:

While salt marshes around the world struggle to keep pace with the ongoing threat of sea level rise, many are further burdened by a history of human disturbance and modification to their tidal channels. In marshes hosting a legacy of salt hay farming, persisting embankments and ditches continue to disrupt natural tidal channel systems even centuries after farming ceases. This history manifests throughout New England salt marshes, visible via satellite as linear and meandering tidal pathways, pools of standing water, and unnaturally abrupt zonation of vegetation. Between historic ditches, increased saturation causes portions of irregularly flooded marsh to shift from Spartina patens, Distichlis spicata, and Juncus gerardii dominance to Spartina alterniflora or to lose vegetation altogether. This loss of vegetation cover can lead to subsidence of the marsh platform and formation of megapools, further altering the marsh hydrology. 

In the face of this ecological threat, SMARTeams (Salt Marsh Adaptation & Resiliency Teams) has devised a four-tiered approach to restoration and management; 1) Halt subsidence trajectories, 2) Optimize accretion/elevation gain, 3) Tune marsh hydrology and vegetation to support obligate wildlife species, and 4) Tend to coastal marshes with adaptive management and long-term stewardship. Here, current monitoring efforts are detailed for pre- and post-restoration marshes in southern coastal Maine in accordance with the SMARTeams approach. 

At each site, transects are established as part of a BACI (Before, After, Control, Impact) design for monitoring vegetation (with point-intercept surveys) and sediment accretion (with feldspar horizons. Wells are also installed for yearly deployment of water level loggers. During restoration, a single channel hydrology network is established using a combination of existing channels, runnels, and ditch remediation. In the following years, runnel dimensions and vegetation responses are monitored to ensure that these built structures are shifting the marsh to an elevation building trajectory. This ongoing work seeks to secure the future of salt marshes as well as the habitat provisioning, climate regulating, and aesthetic services they provide. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8319

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