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
Estuarine Processes, Hazards, and Ecosystems
Coastal Model Applications and Field Measurements- Field Measurements and Model Applications
Estuarine Processes Model Development
Estuarine Processes Model Development
Estuarine Processes Model Development
Estuarine Processes Model Development
Geospatial characterization of salt marshes in Connecticut
Inventory of Managed Coastal Wetlands in Delaware Bay and Delaware's Inland Bays
Lifespan of Massachusetts salt marsh units
Geospatial characterization of salt marshes on the Eastern Shore of Virginia
Lifespan of Chesapeake Bay salt marsh units
Geospatial characterization of salt marshes in Chesapeake Bay
Lifespan of marsh units in Assateague Island National Seashore and Chincoteague Bay, Maryland and Virginia
An Unvegetated to Vegetated Ratio (UVVR) for coastal wetlands of the Conterminous United States (2014-2018)
Climatological Wave Height, Wave Period and Wave Power along Coastal Areas of the East Coast of the United States and Gulf of Mexico
Tidal Datums, Tidal Range, and Nuisance Flooding Levels for Chesapeake Bay and Delaware Bay
COAWST model of Barnegat Bay creeks to demonstrate marsh dynamics
Unvegetated to vegetated marsh ratio in Assateague Island National Seashore and Chincoteague Bay, Maryland and Virginia
Horizontal integrity a prerequisite for vertical stability: Comparison of elevation change and the unvegetated-vegetated marsh ratio across southeastern USA coastal wetlands
Development and application of Landsat-based wetland vegetation cover and unvegetated-vegetated marsh ratio (UVVR) for the conterminous United States
Modeling marsh dynamics using a 3-D coupled wave-flow-sediment model
Quantifying slopes as a driver of forest to marsh conversion using geospatial techniques: Application to Chesapeake Bay coastal-plain, USA
A geospatially resolved wetland vulnerability index: Synthesis of physical drivers
Are elevation and open-water conversion of salt marshes connected?
Understanding tidal marsh trajectories: Evaluation of multiple indicators of marsh persistence
Hydrodynamic and morphologic response of a back-barrier estuary to an extratropical storm
Identifying salt marsh shorelines from remotely sensed elevation data and imagery
Spatial distribution of water level impact to back-barrier bays
Estimating connectivity of hard clam (Mercenaria mercenaria) and eastern oyster (Crassostrea virginica) larvae in Barnegat Bay
Role of tidal wetland stability in lateral fluxes of particulate organic matter and carbon
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.
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.
Sea Level Change
An Interactive Guide to Global and Regional Sea Level Rise Scenarios for the United States
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.
Science and Products
- Science
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...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.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.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.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.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. - Data
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 thInventory 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 classificLifespan 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) scenarioGeospatial 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 delineatedLifespan 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 theGeospatial 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 natioLifespan 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 basedAn 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: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 periodTidal 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 spCOAWST 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 BUnvegetated 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 - Multimedia
- Publications
Filter Total Items: 20
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 reAuthorsNeil K. Ganju, Zafer Defne, Caroline Schwab, Michelle MoormanDevelopment 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 oveAuthorsNeil K. Ganju, Brady Couvillion, Zafer Defne, Kate AckermanModeling 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 COAWSTAuthorsTarandeep S. Kalra, Neil K. Ganju, Alfredo Aretxabaleta, Joel A. Carr, Zafer Defne, Julia MoriartyQuantifying 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 lossAuthorsGrace Damore Molino, Zafer Defne, Alfredo Aretxabaleta, Neil K. Ganju, Joel A. CarrA 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 onAuthorsZafer Defne, Alfredo Aretxabaleta, Neil K. Ganju, Tarandeep S. Kalra, Daniel Jones, Kathryn SmithAre 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 eleAuthorsNeil K. Ganju, Zafer Defne, Sergio FagherazziUnderstanding 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, weAuthorsKerstin 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. RaposaHydrodynamic 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 haAuthorsZafer Defne, Neil K. Ganju, Julia M. MoriartyIdentifying 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 locationAuthorsAmy S. Farris, Zafer Defne, Neil K. GanjuSpatial 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 pAuthorsAlfredo Aretxabaleta, Neil K. Ganju, Zafer Defne, Richard P. SignellEstimating 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 strategiAuthorsJ.D. Goodwin, D.M. Munroe, Zafer Defne, Neil K. Ganju, James VasslidesRole 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 ± 28AuthorsNeil Kamal Ganju, Zafer Defne, Tracy Elsey Quirk, Julia M. Moriarty - Web Tools
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.
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.
Sea Level Change
An Interactive Guide to Global and Regional Sea Level Rise Scenarios for the United States
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.
- News