Research Interests

Predicting how the world’s coastlines will respond to future climate change and human development is complex. Rates of sea-level rise, patterns in storm activity, and the supply of sediment from both marine and fluvial systems will all likely be altered by human activities and changes to our climate. Our interests and expertise extend into a variety of disciplines including natural hazards, physical oceanography, hydrology, and geomorphology, yet the common theme that threads throughout our work is the sourcing, transport and trapping of sediment across coasts, estuaries, and catchments within estuarine and coastal systems.  We are particularly interested in both terrigenous and marine clastic sedimentology and the utilization of sedimentary records to gain insight on coastal flood hazards, beach/marsh complexes and estuarine/tidal-river systems. All of the above-mentioned research interests are framed on societally relevant issues with a focus on how science can improve our management and approach to coastal resilience.

Aerial view of Little River estuary in Wells National Estuarine Research Reserve, Maine

Sediment Dynamics for Coastal Systems  

Sediments serve as the fundamental building block for dynamic coastlines, including coastal bluffs, dunes, beaches, tidal flats, and tidal wetlands (e.g. saltmarshes and mangroves). We are interested in where these sediments come from, how they get from point A to point B, and their role in shaping our ever-evolving shorelines. Our focus is often on coastal resilience and the function of sediments in supporting the integrity of coastal environments and the communities and ecosystems that rely on them. 

UAS-derived DEM at Peggotty Beach, MA

Human modifications to coastal systems:

Coastal systems of the US Northeast are vulnerable to loss given the history of intensive anthropogenic alteration (e.g. coastal armaments, hydrologic alterations, intact marsh plain destruction, tidal restrictions), especially in conditions of accelerating sea level rise. Along exposed coasts, humans have built seawalls and other structures to protect homes and infrastructure from erosion. In salt marshes tidal restrictions, ditching and embankments are prevalent across the Northeast. We are interested in how this legacy infrastructure impacts the function and integrity of salt marsh systems, as well as the evaluation/efficacy of current and proposed restoration strategies.

Ditches

Salt marshes across the US Northeast (ME to VA) are heavily ditched. Ditches increase drainage of the salt marsh platform, resulting in lowered water tables, increased sediment oxygenation, increased decomposition of organic matter, and elevation loss. Additionally, decreased belowground biomass production, reduced sediment delivery, and ditch edge erosion contribute to whole marsh subsidence and loss. Ditching has been observed to decrease overall saltmarsh health. A comprehensive, regional assessment of the influence of ditching on Northeast salt marsh vulnerability to sea level rise is needed. Our overarching goal is to determine how the spatial patterns of salt marsh vulnerability to relative sea level rise across the Northeast US are controlled by ditching, and to assess restoration potential for these vulnerable sites.

Tidal Restrictions

Halophyte (salt-tolerant plant) establishment is key to salt marsh survival. However, halophyte establishment is threatened by accelerating sea level rise as well as built environment stressors; the most common of which are undersized bridges and culverts that restrict tidal flow. Restricted tidal flows freshen marsh soils, release large amounts of methane, and result in impounded conditions that lead to severe subsidence. Tidal flow restoration intended to improve salt marsh health upstream of restriction, in some cases, leads to unvegetated mudflats as the full expanse of tidal exchange is reintroduced. Our research evaluates the extent and causes of marsh vegetation dieback or conversion to mudflat following tidal flow restoration. By diagnosing the main causes of vegetation dieback, we can recommend additional adaptive measures to ensure vegetation recruitment, which local communities value.

Coastal Armoring

We hypothesize that reduced erosion due to coastal armoring has made it harder for salt marshes to survive along urbanizing, armored shorelines, as they no longer receive sediment from eroding coasts. We are testing this hypothesis using satellite imagery to observe how sediment in coastal waters along the Northeast US varies as a function of coastal armoring. Preliminary results suggest that suspended sediment is declining across most regions of the Northeast US. We are analyzing a network of sediment samples and cores from marshes with and without armoring to see if urban marshes receive less sediment following armoring. For marshes failing to keep pace with sea level rise, is coastal armoring and reduced sediment supply part of the problem? And if so, can we find creative solutions to restore this lost sediment that the marshes need? As part of this project, we are working closely with coastal decision-makers to address these questions. Learn more here on this project’s USGS ScienceBase page.

Blue Carbon Science

Blue carbon refers to the carbon that is stored within marine systems. Although coastal ecosystems such as marshes, mangroves, and seagrass beds cover only a small fraction of the global ocean area, they account for up to half of all carbon stored in marine environments, with most of it located in the sediments. Our lab has focused on determining how to leverage predictable spatial patterns in tidal wetland morphology to map blue carbon across intertidal landscapes. To study these spatial patterns, we have adopted remote sensing techniques, which allow us to capture key soil formation processes and control for season and tidal conditions. This is necessary for mapping soil properties and blue carbon across the regional and global spatial scales.

Cartoon of salt marsh blue carbon zonation showing general patterns in marsh soil formation and blue carbon content. Soils tend to be more inorganic (mineral-rich) close to creeks, and more organic-rich further from creeks.
Example maps of marsh soil properties – the maps above show the outputs of our blue carbon modeling work. We used remote sensing indices to model soil organic matter (%) and soil bulk density to derive soil carbon density. One exciting aspect of this work is that we were also able to map mineral sediment content of soils which helps us understand how much sediment is required to maintain marshes across the region.

To explore these geospatial products, you can view maps of soil properties here as a web map here, or download the data from NRCS’s AgDataCommons here.

Occurrence and Impacts of Extreme Flooding Events

Extreme flooding events, including those related to both coastal storm surges and high rainfall-runoff events, play a critical role in the erosion, transport, and redistribution of sediment within landscapes. Our research investigates how the magnitude and frequency of extreme flooding events is changing through time and aims to quantify the impacts of extreme events on sediment mobilization. We utilize sedimentary archives derived from cores collected in lakes, reservoirs, and wetland environments in combination with instrumental observations of modern processes. Past and ongoing research has focused on the western Pacific, Caribbean, and northeast United States. This work seeks to improve our understanding of the evolution of coastal systems, place constraints on flood related hazards, and support planning and management for more resilient coastal systems.

Sketch showing two modes of sediment erosion, transport, and deposition in landscapes from normal / background processes (left) versus extreme flooding events (right) such as hurricanes. We study the sedimentary archives collected with multiple coring techniques to assess the resulting stratigraphy after these flooding events.

Place and Community-Based Science

We are proud members of the new Center for Braiding Indigenous Knowledges and Sciences (CBIKS) and the USGS Northeast Climate Adaptation Science Center(NE CASC). As active participants in these centers we are committed to the mindful development of place-, community-, and indigenous- based research that ethically addresses urgent issues related to climate, food security, and cultural heritage.

Examples of Previous Research Projects Include:

  • Storm reconstructions in Puerto Rico following Hurricane Maria
  • Dams and sediment on the Hudson river (DaSH) investigating the impact of dam removal on the marshes of the Hudson River
  • Reconstructions of extreme flooding in the New York City region following Hurricane Sandy
  • Flood risk evaluations and characterizations for critical beaches of the Massachusetts coast
  • Tsunami and typhoon hazard assessments for southern Japan
  • Impacts and depositional signatures of extreme precipitation by Hurricane Irene
  • The relative impacts of climate change, sea-level rise and shoreline evolution on flooding by cyclones
  • Floodplain trapping of sediment and contaminants along the Connecticut River and estuary