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Zafer Defne, PhD

My research finds its form in providing answers to questions related to coasts and ocean, based on my knowledge of physical oceanography and experience in data sciences.

Dr. Zafer Defne received his PhD in Coastal and Ocean Engineering from Georgia Institute of Technology, with a minor in Information Technology Applications in Oceanography. His expertise includes computational fluid dynamics and data analysis. His work on numerical modeling of coastal ocean has been used to assess storm surge, residual circulation, sediment transport and water quality, as well as marine renewable energy. His recent research is on assessment of the physical state of coastal wetlands using geospatial data.

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Science and Products

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sunset over wetland

Estuarine Processes, Hazards, and Ecosystems

Estuarine processes, hazards, and ecosystems describes several interdisciplinary projects that aim to quantify and understand estuarine processes through observations and numerical modeling. Both the spatial and temporal scales of these mechanisms are important, and therefore require modern instrumentation and state-of-the-art hydrodynamic models. These projects are led from the U.S. Geological...
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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Chesapeake Bay Activities, Woods Hole Coastal and Marine Science Center, Hurricane Sandy, USGS Science in Long Island Sound and its Watershed
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Estuarine Processes, Hazards, and Ecosystems

Estuarine processes, hazards, and ecosystems describes several interdisciplinary projects that aim to quantify and understand estuarine processes through observations and numerical modeling. Both the spatial and temporal scales of these mechanisms are important, and therefore require modern instrumentation and state-of-the-art hydrodynamic models. These projects are led from the U.S. Geological...
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Bathymetry of the New England inner shelf and south shore of Martha’s Vineyard with model grids

Coastal Model Applications and Field Measurements- Field Measurements and Model Applications

Several components of this project are applications to evaluate the model against critical field measurements or to test new model components. Data from field measurements is described in our publications and available in our databases.
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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center
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Coastal Model Applications and Field Measurements- Field Measurements and Model Applications

Several components of this project are applications to evaluate the model against critical field measurements or to test new model components. Data from field measurements is described in our publications and available in our databases.
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Model development output

Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Hurricane Sandy, USGS Science in Long Island Sound and its Watershed
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Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
Learn More
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Model development output

Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Hurricane Sandy, USGS Science in Long Island Sound and its Watershed
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Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
Learn More
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Model development output

Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
By
Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Hurricane Sandy, USGS Science in Long Island Sound and its Watershed
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Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
Learn More
link
Model development output

Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
By
Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Hurricane Sandy, USGS Science in Long Island Sound and its Watershed
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Estuarine Processes Model Development

We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
Learn More
Filter Total Items: 41

Geospatial characterization of salt marshes in Connecticut

This data release contains coastal wetland synthesis products for the state of Connecticut. Metrics for resiliency, including the unvegetated to vegetated ratio (UVVR), marsh elevation, tidal range, wave power, and exposure potential to environmental health stressors are calculated for smaller units delineated from a digital elevation model, providing the spatial variability of physical factors th
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Woods Hole Coastal and Marine Science Center

Inventory of Managed Coastal Wetlands in Delaware Bay and Delaware's Inland Bays

This data release contains areas within Delaware Bay and Delaware Inland Bays that are within tidal elevations, as determined by the Highest Astronomical Tide (HAT), but that are classified as non-tidal or managed wetlands by the National Wetlands Inventory (NWI) or as non-estuarine by the 2016 Coastal Change Analysis Program (C-CAP) land cover dataset. These areas have been assigned the classific
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Woods Hole Coastal and Marine Science Center

Lifespan of Massachusetts salt marsh units

Lifespan of salt marshes in Massachusetts (MA) are calculated using conceptual marsh units defined by Ackerman and others (2022). The lifespan calculation is based on estimated sediment supply and sea-level rise (SLR) predictions after Ganju and others (2020). Sea level predictions are local estimates which correspond to the 0.3, 0.5, and 1.0 meter increase in Global Mean Sea Level (GMSL) scenario
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Woods Hole Coastal and Marine Science Center

Geospatial characterization of salt marshes on the Eastern Shore of Virginia

This data release contains coastal wetland synthesis products for the Atlantic-facing Eastern Shore of Virginia (the data release for the Chesapeake Bay-facing portion of the Eastern Shore of Virginia is found here: https://doi.org/10.5066/P997EJYB). Metrics for resiliency, including unvegetated to vegetated ratio (UVVR), marsh elevation, and tidal range are calculated for smaller units delineated
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Woods Hole Coastal and Marine Science Center

Lifespan of Chesapeake Bay salt marsh units

Lifespan distribution in the Chesapeake Bay (CB) salt marsh complex is presented in terms of lifespan of conceptual marsh units defined by Ackerman and others (2022). The lifespan calculation is based on estimated sediment supply and sea-level rise (SLR) predictions after Ganju and others (2020). Sea level predictions are present day estimates at the prescribed rate of SLR, which correspond to the
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Coastal and Marine Hazards and Resources Program

Geospatial characterization of salt marshes in Chesapeake Bay

This data release contains coastal wetland synthesis products for Chesapeake Bay. Metrics for resiliency, including unvegetated to vegetated ratio (UVVR), marsh elevation, and tidal range are calculated for smaller units delineated from a digital elevation model, providing the spatial variability of physical factors that influence wetland health. The U.S. Geological Survey has been expanding natio
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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Lifespan of marsh units in Assateague Island National Seashore and Chincoteague Bay, Maryland and Virginia

The sediment-based lifespan of salt marsh units in Assateague Island National Seashore (ASIS) and Chincoteague Bay is shown for conceptual marsh units defined by Defne and Ganju (2018). The lifespan represents the timescale by which the current sediment mass within a marsh parcel can no longer compensate for sediment export and deficits induced by sea-level rise. The lifespan calculation is based
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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

An Unvegetated to Vegetated Ratio (UVVR) for coastal wetlands of the Conterminous United States (2014-2018)

This USGS Data Release represents geospatial data sets which were created to produce an Unvegetated to Vegetated Ratio (UVVR) for coastal wetlands of the conterminous United States (2014-2018). The following listed image products were generated 1) Annual spatial datasets (rasters) from 2014 to 2018 each containing 4 bands (Band 1: Unvegetated land fraction; Band 2: Vegetated land fraction; Band 3:
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Chesapeake Bay Activities, Wetland and Aquatic Research Center

Climatological Wave Height, Wave Period and Wave Power along Coastal Areas of the East Coast of the United States and Gulf of Mexico

This U.S. Geological Survey data release provides data on spatial variations in climatological wave parameters (significant wave height, peak wave period, and wave power) for coastal areas along the United States East Coast and Gulf of Mexico. Significant wave height is the average wave height, from crest to trough, of the highest one-third of the waves in a specific time period. Peak wave period
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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Tidal Datums, Tidal Range, and Nuisance Flooding Levels for Chesapeake Bay and Delaware Bay

This U.S. Geological Survey data release provides data on spatial variations in tidal datums, tidal range, and nuisance flooding in Chesapeake Bay and Delaware Bay. Tidal datums are standard elevations that are defined based on average tidal water levels. Datums are used as references to measure local water levels and to delineate regions in coastal environments. Nuisance flooding refers to the sp
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Coastal and Marine Hazards and Resources Program, Chesapeake Bay Activities, Woods Hole Coastal and Marine Science Center

COAWST model of Barnegat Bay creeks to demonstrate marsh dynamics

The COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modeling framework was extended to add two key processes that affect marshes, erosion due to lateral wave thrust (LWT) and vertical accretion due to biomass productivity. The testing of the combined effects of integrating these two processes was done by modeling marsh complexes within Forsythe National Wildlife Refuge and the Barnegat B
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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Unvegetated to vegetated marsh ratio in Assateague Island National Seashore and Chincoteague Bay, Maryland and Virginia

Unvegetated to vegetated marsh ratio (UVVR) in the Assateague Island National Seashore and Chincoteague Bay is computed based on conceptual marsh units defined by Defne and Ganju (2018). UVVR was calculated based on U.S. Department of Agriculture National Agriculture Imagery Program (NAIP) 1-meter resolution imagery. Through scientific efforts initiated with the Hurricane Sandy Science Plan, the U
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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center
USGS logo, U.S. Coastal Wetland Geospatial Collection title and intro text on left. Links to interactive maps on the right
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U.S. Coastal Wetland Geospatial Collection homepage
Collection viewer interactive map with swipe tool to compare data layers
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U.S. Coastal Wetland Geospatial Collection
animated gif showing pre and post storm sediment transport and overwash along the coast
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Pre and Post Hurricane Dorian Aerial Imagery
Example from development of an atmospheric model for Hurricane Florence.
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Hurricane Florence atmospheric model
The animation shows the changing atmospheric pressure and wind fields during the storm as simulated by the model. Arrows display wind direction, colors indicate atmospheric pressure ranging from 97,500 pascals (red) to 102,460 pascals (blue).
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Hurricane Florence atmospheric model
USGS streamflow and rain gages, and Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) gages are shown.
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Hurricane Florence numerical modeling
Hurricane Florence numerical modeling
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Hurricane Florence numerical modeling
offshore surge and offshore waves coastal models
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Model output of offshore surges and waves
Photo of a boardwalk over a saltmarsh creek showing people
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Social benefits of marshes
Photo showing floating cages for oyster farming in a marsh creek exposed at low tide.
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Economic benefits of marshes
Photo showing different species of salt tolerant plants near a saltmarsh
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Saltmarsh vegetation
Photo of a saltmarsh platform showing vegetation on on top of the banks of a tidal creek.
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A saltmarsh platform
dynamic image of offshore flooding in the Cape Fear River Estuary
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Compound Flooding in the Cape Fear River Estuary
Edwin B. Forsythe National Wildlife Refuge, New Jersey Study SIte
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Study site for Edwin B. Forsythe National Wildlife Refuge, New Jersey
Browse graphic of Edwin B Forsythe National Wildlife Refuge study area
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Edwin B Forsythe National Wildlife Refuge study area
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Horizontal integrity a prerequisite for vertical stability: Comparison of elevation change and the unvegetated-vegetated marsh ratio across southeastern USA coastal wetlands

Surface elevation tables (SETs) estimate the vertical resilience of coastal wetlands to sea-level rise (SLR) and other stressors but are limited in their spatial coverage. Conversely, spatially integrative metrics based on remote sensing provide comprehensive spatial coverage of horizontal processes but cannot track elevation trajectory at high resolution. Here, we present a critical advance in re
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Neil K. Ganju, Zafer Defne, Caroline Schwab, Michelle Moorman
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Woods Hole Coastal and Marine Science Center

Development and application of Landsat-based wetland vegetation cover and unvegetated-vegetated marsh ratio (UVVR) for the conterminous United States

Effective management and restoration of salt marshes and other vegetated intertidal habitats require objective and spatially integrated metrics of geomorphic status and vulnerability. The unvegetated-vegetated marsh ratio (UVVR), a recently developed metric, can be used to establish present-day vegetative cover, identify stability thresholds, and quantify vulnerability to open-water conversion ove
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Neil K. Ganju, Brady Couvillion, Zafer Defne, Kate Ackerman
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Ecosystems Mission Area, Coastal and Marine Hazards and Resources Program, Wetland and Aquatic Research Center , Woods Hole Coastal and Marine Science Center

Modeling marsh dynamics using a 3-D coupled wave-flow-sediment model

Salt marshes are dynamic biogeomorphic systems that respond to external physical factors, including tides, sediment transport, and waves, as well as internal processes such as autochthonous soil formation. Predicting the fate of marshes requires a modeling framework that accounts for these processes in a coupled fashion. In this study, we implement two new marsh dynamic processes in the 3-D COAWST
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Tarandeep S. Kalra, Neil K. Ganju, Alfredo Aretxabaleta, Joel A. Carr, Zafer Defne, Julia Moriarty
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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Quantifying slopes as a driver of forest to marsh conversion using geospatial techniques: Application to Chesapeake Bay coastal-plain, USA

Coastal salt marshes, which provide valuable ecosystem services such as flood mitigation and carbon sequestration, are threatened by rising sea level. In response, these ecosystems migrate landward, converting available upland into salt marsh. In the coastal-plain surrounding Chesapeake Bay, United States, conversion of coastal forest to salt marsh is well-documented and may offset salt marsh loss
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Grace Damore Molino, Zafer Defne, Alfredo Aretxabaleta, Neil K. Ganju, Joel A. Carr
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Ecosystems Mission Area, Climate Research and Development Program, Land Change Science Program, Eastern Ecological Science Center, Chesapeake Bay Activities, Woods Hole Coastal and Marine Science Center

A geospatially resolved wetland vulnerability index: Synthesis of physical drivers

Assessing wetland vulnerability to chronic and episodic physical drivers is fundamental for establishing restoration priorities. We synthesized multiple data sets from E.B Forsythe National Wildlife Refuge, New Jersey, to establish a wetland vulnerability metric that integrates a range of physical processes, regulatory information and physical/biophysical features. The geospatial data are based on
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Zafer Defne, Alfredo Aretxabaleta, Neil K. Ganju, Tarandeep S. Kalra, Daniel Jones, Kathryn Smith
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Woods Hole Coastal and Marine Science Center

Are elevation and open-water conversion of salt marshes connected?

Salt marsh assessments focus on vertical metrics such as accretion or lateral metrics such as open-water conversion, without exploration of how the dimensions are related. We exploited a novel geospatial dataset to explore how elevation is related to the unvegetated-vegetated marsh ratio (UVVR), a lateral metric, across individual marsh “units” within four estuarine-marsh systems. We find that ele
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Neil K. Ganju, Zafer Defne, Sergio Fagherazzi
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Woods Hole Coastal and Marine Science Center

Understanding tidal marsh trajectories: Evaluation of multiple indicators of marsh persistence

Robust assessments of ecosystem stability are critical for informing conservation and management decisions. Tidal marsh ecosystems provide vital services, yet are globally threatened by anthropogenic alterations to physical and biological processes. A variety of monitoring and modeling approaches have been undertaken to determine which tidal marshes are likely to persist into the future. Here, we
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Kerstin Wasson, Neil K. Ganju, Zafer Defne, Charlie Endris, Tracy Elsey-Quirk, Karen M. Thorne, Chase M. Freeman, Glenn R. Guntenspergen, Daniel J. Nowacki, Kenneth B. Raposa
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Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Western Ecological Research Center (WERC), Woods Hole Coastal and Marine Science Center

Hydrodynamic and morphologic response of a back-barrier estuary to an extratropical storm

We investigated the hydrodynamic and morphologic response of Barnegat Bay-Little Egg Harbor, New Jersey, USA to Hurricane Sandy. We implemented a three-dimensional, coupled ocean-wave-sediment transport model of the estuary and explored the role of offshore water levels, offshore waves, local winds and waves by systematically removing forcings from a series of simulations. Offshore water levels ha
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Zafer Defne, Neil K. Ganju, Julia M. Moriarty
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Woods Hole Coastal and Marine Science Center

Identifying salt marsh shorelines from remotely sensed elevation data and imagery

Salt marshes are valuable ecosystems that are vulnerable to lateral erosion, submergence, and internal disintegration due to sea-level rise, storms, and sediment deficits. Because many salt marshes are losing area in response to these factors, it is important to monitor their lateral extent at high resolution over multiple timescales. In this study we describe two methods to calculate the location
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Amy S. Farris, Zafer Defne, Neil K. Ganju
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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Spatial distribution of water level impact to back-barrier bays

Water level in semi-enclosed bays, landward of barrier islands, is mainly driven by offshore sea level fluctuations that are modulated by bay geometry and bathymetry, causing spatial variability in the ensuing response (transfer). Local wind setup can have a secondary role that depends on wind speed, fetch, and relative orientation of the wind direction and the bay. Inlet geometry and bathymetry p
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Alfredo Aretxabaleta, Neil K. Ganju, Zafer Defne, Richard P. Signell
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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Pacific Coastal and Marine Science Center

Estimating connectivity of hard clam (Mercenaria mercenaria) and eastern oyster (Crassostrea virginica) larvae in Barnegat Bay

Many marine organisms have a well-known adult sessile stage. Unfortunately, our lack of knowledge regarding their larval transient stage hinders our understanding of their basic ecology and connectivity. Larvae can have swimming behavior that influences their transport within the marine environment. Understanding the larval stage provides insight into population connectivity that can help strategi
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J.D. Goodwin, D.M. Munroe, Zafer Defne, Neil K. Ganju, James Vasslides
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Woods Hole Coastal and Marine Science Center

Role of tidal wetland stability in lateral fluxes of particulate organic matter and carbon

Tidal wetland fluxes of particulate organic matter and carbon (POM, POC) are important terms in global budgets but remain poorly constrained. Given the link between sediment fluxes and wetland stability, POM and POC fluxes should also be related to stability. We measured POM and POC fluxes in eight microtidal salt marsh channels, with net POM fluxes ranging between −121 ± 33 (export) and 102 ± 28
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Neil Kamal Ganju, Zafer Defne, Tracy Elsey Quirk, Julia M. Moriarty
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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Hurricane Florence Numerical Modeling

The U.S. Geological Survey (USGS) has partnered with North Carolina State University (NCSU), Louisiana State University (LSU) and University Corporation for Atmospheric Research (UCAR) to investigate hurricane-induced compound flooding and sediment dispersal using coupled hydrology and ocean models. 

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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Hurricane Florence, Hurricanes

National UVVR Map

This map shows the unvegetated and vegetated area of coastal wetlands and adjacent land (inland and shorelines) for the Conterminous United States computed from 2014-2018 Landsat imagery at ~30 meter horizontal resolution.  

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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Sea Level Change

An Interactive Guide to Global and Regional Sea Level Rise Scenarios for the United States

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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Sea Level Change: An Interactive Guide to Global and Regional Sea Level Rise Scenarios for the United States

In collaboration with USGS researchers, The Sea Level Rise and Coastal Flood Hazard Scenarios and Tools Interagency Task Force convened by the U.S. Ocean Policy Committee and the U.S. Global Change Research Program has developed two products that provides users with information and a tool to visualize, interact with, and explore 2017 sea-level rise scenarios.

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Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Hurricanes
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Now Available: First CONUS-wide Coastal Wetland Collection

Scientists from across USGS have created the first CONUS-wide collection of key tidal wetland metrics. These metrics provide data on habitat quality...

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Assessing Salt Marsh Vulnerability Nationwide

Salt marshes are among the most productive and valuable ecosystems in the world. The vegetation in these coastal systems acts as a buffer between land...

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