Defne, Z., N. K. Ganju, and A. Aretxabaleta
(2016), Estimating time-dependent
connectivity in marine systems, Geophys.
Res. Lett., 43, doi:10.1002/2015GL066888.
Neil Kamal Ganju, PhD
My research spans the multiple disciplines that converge in estuarine systems. Research projects include numerical model development, field observations of hydrodynamics and water quality, wetland and coastal vulnerability assessments, geomorphic change, and eutrophication. For more details, visit http://woodshole.er.usgs.gov/project-pages/estuaries/
Biography
I studied civil engineering at the University of Michigan (BSCE), the University of Florida (MSCE), and the University of California-Davis (Ph.D.). In 2001, I began working for the USGS at the California Water Science Center, on the San Francisco Bay Sediment Transport Project with Dr. David Schoellhamer. In 2008 I moved to the Woods Hole Coastal and Marine Science Center and began multiple projects throughout the northeast US. The Estuarine Processes, Hazards, and Ecosystems project, started in 2015, details the past and ongoing studies we are involved with.
Science and Products
Date published: August 6, 2019
Status: Active Coastal System Change at Fire Island, New York
Fire Island is a 50-km long barrier island along the south shore of Long Island, New York. The island is comprised of seventeen year-round communities; federal, state, and county parks; and supports distinct ecosystems alongside areas of economic and cultural value. In addition to providing resources to its residents, the barrier island also protects the heavily-populated mainland from storm...
Date published: May 2, 2019
Status: Active Back-barrier and Estuarine - Coastal System Change at Fire Island, New York
Regional-scale modeling forecasts how atmospheric forcing and oceanographic circulation influence estuarine circulation and water levels, sediment transport, and wetland change.
Contacts: Neil Kamal Ganju, PhD, Alfredo Aretxabaleta , PhD
Attribution: St. Petersburg Coastal and Marine Science Center
Date published: February 21, 2019
Status: Active Estuarine Processes, Hazards, and Ecosystems-Study Sites
Estuaries are dynamic environments where complex interactions between the atmosphere, ocean, watershed, ecosystems, and human infrastructure take place. They serve as valuable ecological habitat and provide numerous ecosystem services and recreational opportunities. However, they are modified by physical processes such as storms and sea-level rise, while anthropogenic impacts such as nutrient...
Contacts: Neil Kamal Ganju, PhD
Date published: February 1, 2019
Status: Active 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....
Date published: December 28, 2018
Status: Active Hurricane Sandy Response- Linking the Delmarva Peninsula's Geologic Framework to Coastal Vulnerability
The Delmarva Peninsula is a 220-kilometer-long headland, spit, and barrier island complex that was significantly affected by Hurricane Sandy. In order to better constrain controls on coastal vulnerability and evolution, the region’s sediment sources, transport pathways and sediment sinks must be identified. This project defines the geologic framework of the Delmarva coastal system through...
Date published: August 31, 2018
Status: Active 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.
Date published: August 28, 2018
Status: Active Coastal Model Applications and Field Measurements
Numerical models are used by scientists, engineers, coastal managers, and the public to understand and predict processes in the coastal ocean. This project supports the development and application of open-source coastal models and has several objectives: 1) improve the code of numerical sediment-transport models by implementing new or improved algorithms; 2) obtain measurements of coastal...
Date published: March 5, 2018
Status: Active Estuarine Processes Eutrophication
Increased loadings of nutrients to estuaries have altered ecosystem function by encouraging growth of phytoplankton and macroalgae while inducing large swings in dissolved oxygen and threatening the sustainability of seagrass meadows. We are measuring and modeling these processes to understand the future trajectory of estuarine ecosystems.
Date published: March 5, 2018
Status: Active Estuarine Processes Tidal Wetlands
Tidal wetlands are an important geomorphic and ecological feature of the coastal zone. Our projects deal with the physical forcings that affect wetland stability over event-to-annual timescales, including wave attack, sediment supply, and sea-level rise.
Date published: March 5, 2018
Status: Active Estuarine Processes Coastal Hazards
Extreme tides and coastal storms transfer high water levels to estuaries through natural and managed entrances. The size of the transfer depends on the duration of the event and the geomorphology of the estuary. We use observational data and modeling scenarios to understand and spatially map this transfer at our study sites.
Date published: March 5, 2018
Status: Active 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.
Date published: October 18, 2021
Idealized COAWST numerical model for testing marsh wave thrust and lateral retreat dynamics routines
There are two idealized domains developed in this work to test the marsh dynamics in the COAWST modeling framework.
1. First idealized domain is to test and verify the lateral thrust calculations.
2. Second idealized domain is to test the implementation of lateral retreat formulations
Date published: October 18, 2021
COAWST model of Barnegat Bay creeks to demonstrate marsh dynamics
The COAWST 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 Bay estuary, New Jersey.
Date published: September 30, 2021
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.
Date published: September 17, 2021
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.
Date published: September 17, 2021
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...
Date published: May 24, 2021
Coastal Wetlands of Blackwater salt marsh complex, 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.
Date published: February 17, 2021
Geochemical data supporting investigation of solute and particle cycling and fluxes from two tidal wetlands on the south shore of Cape Cod, Massachusetts, 2012-19
The U.S. Geological Survey and collaborators collected surface water and porewater geochemical data from a tidal wetland located on the eastern shore of Sage Lot Pond in Mashpee, Massachusetts, within the Waquoit Bay National Estuarine Research Reserve, between 2012 and 2019.
Date published: July 21, 2020
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...
Date published: June 2, 2020
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...
Date published: June 2, 2020
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...
Date published: March 31, 2020
Coastal wetlands of eastern Long Island, New York
This data release contains coastal wetland synthesis products for the geographic region of eastern Long Island, New York, including the north and south forks, Gardiners Island, and Fishers Island. 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.
Date published: November 26, 2019
U.S. Geological Survey hydrodynamic model simulations for Barnegat Bay, New Jersey, during Hurricane Sandy, 2012
We used the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST; Warner and others, 2010) model to simulate ocean circulation, waves, and sediment transport in Barnegat Bay, New Jersey, during Hurricane Sandy. The simulation period was from October 27 to November 4, 2012. We used a 2012 digital terrain model (Andrews and others, 2015) to prescribe the prestorm bathymetry.
Year Published: 2021
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...
Molino, Grace Damore; Defne, Zafer; Aretxabaleta, Alfredo; Ganju, Neil Kamal; Carr, Joel A.Attribution: Chesapeake Bay Activities, Eastern Ecological Science Center, Patuxent Wildlife Research Center, Woods Hole Coastal and Marine Science Center, Ecosystems, Climate Research and Development Program, Land Change Science Program, Region 1: North Atlantic-Appalachian, United States of America
Year Published: 2021
Sediment dynamics of a divergent bay–marsh complex
Bay–marsh systems, composed of an embayment surrounded by fringing marsh incised by tidal channels, are widely distributed coastal environments. External sediment availability, marsh-edge erosion, and sea-level rise acting on such bay–marsh complexes may drive diverse sediment-flux regimes. These factors reinforce the ephemeral and dynamic nature...
Nowacki, Daniel J. ; Ganju, Neil KamalAttribution: Coasts, Geology, Pacific Coastal and Marine Science Center, Woods Hole Coastal and Marine Science Center, Natural Hazards, Coastal and Marine Hazards and Resources Program, Region 1: North Atlantic-Appalachian, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Region 4: Mississippi Basin, Region 10: California-Great Basin, Alabama, Mississippi, United States of America
Year Published: 2021
Applying cumulative effects to strategically advance large‐scale ecosystem restoration
International efforts to restore degraded ecosystems will continue to expand over the coming decades, yet the factors contributing to the effectiveness of long‐term restoration across large areas remain largely unexplored. At large scales, outcomes are more complex and synergistic than the additive impacts of individual restoration projects. Here...
Diefenderfer, Heida L.; Steyer, Gregory; Harwell, Matthew C.; LoSchiavo, Andrew J; Neckles, Hilary A.; Burdick, David M.; Johnson, Gary E.; Buenau, Kate E.; Trujillo, Elene; Callaway, John C.; Thom, Ronald M.; Ganju, Neil Kamal; Twilley, Robert R.
Year Published: 2021
Sediment budget estimates for a highly impacted embayment with extensive wetland loss
External sediment supply is an important control on wetland morphology and vulnerability to storms, sea-level rise, and land use change. Constraining sediment supply and net budgets is difficult due to multiple timescales of variability in hydrodynamic forcing and suspended-sediment concentrations, as well as the fundamental limitations of...
Chant, Robert; Ralston, David K.; Ganju, Neil Kamal; Pianca, Casia; Simonson, Amy; Cartwright, Richard
Year Published: 2020
Development of a submerged aquatic vegetation growth model in the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST v3.4) model
The coupled biophysical interactions between submerged aquatic vegetation (SAV), hydrodynamics (currents and waves), sediment dynamics, and nutrient cycling have long been of interest in estuarine environments. Recent observational studies have addressed feedbacks between SAV meadows and their role in modifying current velocity, sedimentation, and...
Kalra, Tarandeep S.; Ganju, Neil Kamal; Testa, Jeremy M.
Year Published: 2020
Simulated estuary-wide response of seagrass (Zostera marina) to future scenarios of temperature and sea level
Seagrass communities are a vital component of estuarine ecosystems, but are threatened by projected sea level rise (SLR) and temperature increases with climate change. To understand these potential effects, we developed a spatially explicit model that represents seagrass (Zostera marina) habitat and estuary-wide productivity for Barnegat Bay-...
Scalpone, Cara; Jarvis, Jessie; Vasslides, James; Testa, Jeremy; Ganju, Neil Kamal
Year Published: 2020
Sediment delivery to marsh platforms minimized by source decoupling and flux convergence
Sediment supply is a primary factor in determining marsh response to sea level rise and is typically approximated through high‐resolution measurements of suspended sediment concentrations (SSCs) from adjacent tidal channels. However, understanding sediment transport across the marsh itself remains limited by discontinuous measurements of SSC over...
Coleman, Daniel; Ganju, Neil Kamal; Kirwan, Matthew
Year Published: 2020
A non-linear relationship between marsh size and sediment trapping capacity compromises salt marshes’ resilience to sea-level rise
Global assessments predict the impact of sea-level rise on salt marshes with present-day levels of sediment supply from rivers and the coastal ocean. However, these assessments do not consider that variations in marsh extent and the related reconfiguration of intertidal area affect local sediment dynamics, ultimately controlling the fate of the...
Donatelli, Carmine; Zhang, Xiaohe; Ganju, Neil Kamal; Aretxabaleta, Alfredo; Fagherazzi, Sergio; Leonardi, Nicoletta
Year Published: 2020
Representing the function and sensitivity of coastal interfaces in Earth system models
Along coastal interfaces, components of the Earth system interact to regulate ecosystem functions and Earth’s climate. Between the land and ocean, diverse coastal ecosystem types transform, store, and transport material. A dynamic two-way exchange of energy and matter is driven by hydrological and marine processes such as river and groundwater...
Ward, Nicholas; Megonigal, J. Patrick; Bond-Lamberty, Ben; Bailey, Vanessa; Butman, David; Canuel, Elizabeth; Diefenderfer, Heida; Ganju, Neil Kamal; Goni, Miguel; Graham, Emily B.; Hopkinson, Charles; Khangaonkar, Tarang; Langley, Adam; McDowell, Nate; Myers-Pigg, Allison; Neumann, Rebecca; Osburn, Christopher; Price, Rene; Rowland, Joel; Sengupta, Aditi; Simard, Marc; Thornton, Peter E.; Tzortziou, Maria; Vargas, Rodrigo; Weisenhorn, Pamela; Windham-Myers, LisamarieAttribution: Water Resources
Year Published: 2020
Spatiotemporal variability of light attenuation and net ecosystem metabolism in a back-barrier estuary
Quantifying system-wide biogeochemical dynamics and ecosystem metabolism in estuaries is often attempted using a long-term continuous record at a single site or short-term records at multiple sites due to sampling limitations that preclude long-term monitoring. However, differences in the dominant primary producer at a given location (e.g.,...
Ganju, Neil Kamal; Testa, Jeremy; Suttles, Steven E.; Aretxabaleta, Alfredo
Year Published: 2020
Determining the drivers of suspended sediment dynamics in tidal marsh-influenced estuaries using high-resolution ocean color remote sensing
Sediment budgets are a critical metric to assess coastal marsh vulnerability to sea-level rise and declining riverine sediment inputs. However, calculating accurate sediment budgets is challenging in tidal marsh-influenced estuaries where suspended sediment concentrations (SSC) typically vary on scales of hours and meters, and where SSC dynamics...
Zhang, Xiaohe; Fichot, Cedric; Baracco, Carly; Guo, Ruizhe; Neugebauer, Sydney; Bengtsson, Zachary; Ganju, Neil Kamal; Fagherazzi, Sergio
Year Published: 2020
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/...
Defne, Zafer; Aretxabaleta, Alfredo; Ganju, Neil Kamal; Kalra, Tarandeep S.; Jones, Daniel K.; Smith, KathrynPre-USGS Publications
Ganju, N. K., Brush, M. J., Rashleigh, B., Aretxabaleta, A. L., del Barrio, P., Grear, J. S., ... & Vaudrey, J. M., 2015, Progress and challenges in coupled hydrodynamic-ecological estuarine modeling, Estuaries and Coasts, 1-22.
Ganju, N.K., Jaffe, B.E., and Schoellhamer, D.H., 2011, Discontinuous hindcast simulations of estuarine bathymetric change: a case study from Suisun Bay, California. Estuarine, Coastal and Shelf Science, 93, 142-150.
Ganju, N.K., and Schoellhamer, D.H., 2006, Annual sediment flux estimates in a tidal strait using surrogate measurements. Estuarine, Coastal and Shelf Science, 69, 165-178.
Ganju, N.K., Schoellhamer, D.H., and Jaffe, B.E., 2009, Hindcasting of decadal-timescale estuarine bathymetric change with a tidal-timescale model. Journal of Geophysical Research-Earth Surface, 114, F04019, doi:10.1029/2008JF001191.
Ganju, N.K., Schoellhamer, D.H., Warner, J.C., Barad, M.F., and Schladow, S.G., 2004, Tidal oscillation of sediment between a river and a bay: a conceptual model. Estuarine, Coastal and Shelf Science, 60(1), 81-90.
Ganju, N.K., and Sherwood, C.R., 2010, Effect of roughness formulation on the performance of a coupled wave, hydrodynamic, and sediment transport model. Ocean Modelling, 33, 299-313.
Gartner, J.W., and Ganju, N.K., 2007, Correcting acoustic Doppler current profiler discharge measurement bias from moving-bed conditions without global positioning during the 2004 Glen Canyon Dam controlled flood on the Colorado River. Limnology and Oceanography: Methods, 5, 156-162.
Leonardi, N., Ganju, N.K. and Fagherazzi, S., 2016. A linear relationship between wave power and erosion determines salt-marsh resilience to violent storms and hurricanes. Proceedings of the National Academy of Sciences, 113(1), pp.64-68.
Kirincich, A. R., Lentz, S. J., Farrar, J. T., and Ganju, N. K., 2013, The Spatial Structure of Tidal and Mean Circulation over the Inner Shelf South of Martha's Vineyard, Massachusetts. Journal of Physical Oceanography, 43(9).
Miselis, J.L., Andrews, B.D., Nicholson, R.S., Defne, Z., Ganju, N.K. and Navoy, A., 2015. Evolution of mid-Atlantic coastal and back-barrier estuary environments in response to a hurricane: Implications for barrier-estuary connectivity. Estuaries and Coasts, pp.1-19.
Oestreich, W. K., Ganju, N. K., Pohlman, J. W., and Suttles, S. E., 2016. Colored dissolved organic matter in shallow estuaries: relationships between carbon sources and light attenuation, Biogeosciences, 13, 583-595, doi:10.5194/bg-13-583-2016.
Rosencranz, J.A., Ganju, N.K., Ambrose, R.F., Brosnahan, S.M., Dickhudt, P.J., Guntenspergen, G.R., MacDonald, G.M., Takekawa, J.Y, and Thorne, K.M., 2015, Balanced sediment fluxes in southern California’s Mediterranean-climate zone salt marshes, Estuaries and Coasts, DOI 10.1007/s12237-015-0056-y.
Date published: March 17, 2021
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 and sea. This natural buffer helps reduce flooding, erosion, and subsequent damage to property and infrastructure by slowing down the flow of water and dissipating waves during storms.
Date published: August 31, 2018
Raising Awareness in the Classroom about Natural Hazards Facing U.S. Coastal Communities
USGS scientists present newly developed education outreach materials at the Smithsonian Science Education Academy for Teachers (SSEATs) held at the USGS National Headquarters in Reston, Virginia.
Date published: May 3, 1999
Focus on Estuaries and Coastal Wetlands
Estuaries and wetlands provide a critical defense against storms and sea-level rise while providing economically valuable services. How well they protect coastal communities and host diverse ecosystems is largely a function of their shape (morphology), which is controlled by factors such as sediment movement and biological feedbacks.