Geology topics

Michelle A. Hummel

Publications and source records attributed to Michelle A. Hummel.

3 recordsLinked to original sources

USGS2026

Ecogeomorphologic response of a tidally restricted salt marsh to tidal restoration and sea-level rise

Diked marshes with decades of restricted tidal flow exhibit fundamentally altered hydrologic and ecologic dynamics that result in limited vertical accretion, land subsidence, and underdeveloped tidal channels. These changes complicate marsh restoration efforts and constrain the marsh's ability to build elevation in response to future sea levels. In this study, we developed an integrated hydrodynamic and marsh accretion model to conduct the first assessment of the restoration potential of a diked marsh in response to reintroduction of tidal flow and sea-level rise (SLR). We applied our model to evaluate changes in biomass production in the Herring River estuary, Cape Cod, MA, USA—which has experienced significant ecological shifts due to more than a century of tidal restriction—in response to a range of SLR scenarios, tidal flow conditions, management interventions, and biomass production rates through 2100. We found that with restoration of tidal flow, the simulated marsh extent expanded in areas with efficient drainage, increasing biomass production by up to 4.4 times. However, when SLR was imposed, parts of the marsh gradually transitioned to open water, leading to a decline in marsh coverage from 19% to as low as 12%. Management interventions aimed at enhancing marsh elevation and improving the drainage capacity of tidal channels slowed marsh loss, supporting marsh area through 2100. Our findings provide insight into the key drivers of marsh resilience and loss, and our approach can be applied across tidally restricted and restored systems to develop targeted, adaptive restoration strategies that achieve desired ecological outcomes.

Massachusetts↗

USGS2024

Hydrodynamic and salinity tesponse to tidal restoration in the Herring River Estuary, MA, considering present and future sea levels

Coastal salt marshes are crucial ecosystems that provide habitat for a variety of species, improve water quality, and play a major role in the global carbon cycle. However, many salt marshes have been severely damaged by human activities such as diking and draining for urban development. Recently, there has been a noticeable shift toward the prioritization of coastal marsh restoration to re-establish their ecosystem services. The removal of anthropogenic barriers such as dikes, sluices, and culverts is a critical component of many projects because it allows for the restoration of tidal flow to support natural hydrologic regimes and salinity conditions, which play a dominant role in determining the ecological and biogeochemical functioning of marshes. This study examines how proposed removal of hydraulic structures will influence the hydrologic potential for marsh restoration in the Herring River Estuary in Cape Cod, Massachusetts, USA. Construction of dikes, roadways, and low-capacity culverts over the last century has substantially restricted tidal flow in the Herring River Estuary, leading to degradation of salt marsh habitat. The estuary is now undergoing the first phase of a restoration project to re-introduce natural hydrologic conditions, increase salinity, and restore salt marsh habitat. To assess how the Herring River Estuary will respond to human- and climate-driven modifications, we develop and apply a validated hydrodynamic model to simulate the complex tidal and salinity dynamics of the estuary under a range of restoration and sea level rise scenarios. We then quantify how salinity and critical hydrologic variables, including tidal range and depth of mean high water, will evolve for various restoration scenarios considering present and future sea levels. The results of this research can inform coastal management and restoration plans that re-create the natural functioning of the system while protecting critical infrastructure and reducing the risk of restoration failure.

Massachusetts↗

USGS2023

Future marsh evolution due to tidal changes induced by human adaptation to sea level rise

With sea level rise threatening coastal development, decision-makers are beginning to act by modifying shorelines. Previous research has shown that hardening or softening shorelines may change the tidal range under future sea level rise. Tidal range can also be changed by natural factors. Coastal marshes, which humans increasingly depend on for shoreline protection, are ecologically sensitive to tidal range. Therefore, it is critical to examine how changes in tidal range could influence marsh processes. A marsh accretion model was used to investigate the ecological response of a San Francisco Bay, California, USA marsh to multiple tidal range scenarios and sea level rise from 2010 to 2100. The scenarios include a baseline scenario with no shoreline modifications in the estuary, a shoreline hardening scenario that amplifies the tidal range, and 14 tidal range scenarios as a sensitivity analysis that span tidal amplification and reduction of the baseline scenario. The modeling results expose key tradeoffs to consider when planning for sea level rise. Compared to the baseline, the hardening scenario shows minor differences. However, further tidal amplification prolongs marsh survival but decreases Sarcocornia pacifica cover, an important species for certain threatened wildlife and an effective attenuator of wave energy. Conversely, tidal reduction precipitates marsh drowning but shows gains in Sarcocornia pacifica cover. These mixed impacts of tidal amplification and reduction shown by the model indicate potential tradeoffs in relation to marsh survival, habitat characteristics, and shoreline protection. This study suggests the need for a cross-sectoral, regional approach to sea level rise adaptation.

California↗