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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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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, Coastal and Marine Hazards and Resources Program, Chesapeake Bay Activities, Woods Hole Coastal and Marine Science Center
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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, 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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Filter Total Items: 34

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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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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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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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, 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

Geospatial Characterization of Salt Marshes for Massachusetts

This data release contains coastal wetland synthesis products for Massachusetts. 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 nation
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Wave thrust values at point locations along the shorelines of Massachusetts and Rhode Island

This product provides spatial variations in wave thrust along shorelines in Massachusetts and Rhode Island. Natural features of relevance along the State coast are salt marshes. In recent times, marshes have been eroding primarily through lateral erosion. Wave thrust represents a metric of wave attack acting on marsh edges. The wave thrust is calculated as the vertical integral of the dynamic pres
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Wave thrust values at point locations along the shorelines of Chesapeake Bay, Maryland and Virginia

This product provides spatial variations in wave thrust along shorelines in the Chesapeake Bay. Natural features of relevance along the Bay coast are salt marshes. In recent times, marshes have been eroding primarily through lateral erosion. Wave thrust represents a metric of wave attack acting on marsh edges. The wave thrust is calculated as the vertical integral of the dynamic pressure of waves.
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Chesapeake Bay Activities, Woods Hole Coastal and Marine Science Center

Coastal wetlands of the Blackwater region, Chesapeake Bay, Maryland

This data release contains coastal wetland synthesis products for the geographic region of Blackwater, Chesapeake Bay, Maryland. Metrics for resiliency, including unvegetated to vegetated ratio (UVVR), marsh elevation, and others, 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.
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Chesapeake Bay Activities, Woods Hole Coastal and Marine Science Center

Coastal wetlands of Hudson Valley and New York City, New York

This data release contains coastal wetland synthesis products for the geographic region of Hudson Valley and New York City, New York. Metrics for resiliency, including unvegetated to vegetated ratio (UVVR), marsh elevation, and mean tidal range, are calculated for smaller units delineated from a Digital Elevation Model, providing the spatial variability of physical factors that influence wetland h
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Woods Hole Coastal and Marine Science Center

Coastal wetlands of north shore Long Island, New York

This data release contains coastal wetland synthesis products for the geographic region of north shore Long Island, New York. Metrics for resiliency, including unvegetated to vegetated ratio (UVVR), marsh elevation, and mean tidal range, are calculated for smaller units delineated from a Digital Elevation Model, providing the spatial variability of physical factors that influence wetland health. T
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Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Slope Values Across Marsh-Forest Boundary in Chesapeake Bay Region, USA

The marsh-forest boundary in the Chesapeake Bay was determined by geoprocessing high-resolution (1 square meter) land use and land cover data sets. Perpendicular transects were cast at standard intervals (30 meters) along the boundary within a GIS by repurposing the Digital Shoreline Analysis System (DSAS) Version 5.0, an ArcGIS extension developed by the U.S. Geological Survey. Average and maximu
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Coastal and Marine Hazards and Resources Program, Chesapeake Bay Activities, Woods Hole Coastal and Marine Science Center
Filter Total Items: 17

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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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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Ecosystems, Climate Research and Development Program, Land Change Science Program, Eastern Ecological Science Center, Chesapeake Bay Activities, Patuxent Wildlife Research Center, 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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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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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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Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Patuxent Wildlife Research 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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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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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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Natural Hazards, 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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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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Natural Hazards, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Physical response of a back-barrier estuary to a post-tropical cyclone

This paper presents a modeling investigation of the hydrodynamic and sediment transport response of Chincoteague Bay (VA/MD, USA) to Hurricane Sandy using the Coupled Ocean-Atmosphere-Wave-Sediment-Transport (COAWST) modeling system. Several simulation scenarios with different combinations of remote and local forces were conducted to identify the dominant physical processes. While 80% of the water
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Woods Hole Coastal and Marine Science Center

Spatially integrative metrics reveal hidden vulnerability of microtidal salt marshes

Salt marshes are valued for their ecosystem services, and their vulnerability is typically assessed through biotic and abiotic measurements at individual points on the landscape. However, lateral erosion can lead to rapid marsh loss as marshes build vertically. Marsh sediment budgets represent a spatially integrated measure of competing constructive and destructive forces: a sediment surplus may r
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Woods Hole Coastal and Marine Science Center

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, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center

Coastal Wetlands: The State and Future of a Precious Resource

Coastal wetlands, and salt marshes specifically, are simultaneously geomorphic and biologic systems. They proliferate across a narrow range of elevation, water level, and salinity conditions. Salt marshes rely on their own growth and sediment input to maintain or increase their extent, whereas physical forces such as waves and sea-level rise tend to reduce it. 

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