Fiscal Year: 2022

Project Description: The aim of this project was to examine how physical conditions in Jamaica Bay including water level, waves, and sediment transport respond to extreme storm events. To address this, we developed a coupled, nested modeling framework for the domain and simulated a range of forcing conditions. The work was highly collaborative with project team members at the USGS and the Stevens Institute.

The modeling efforts had several distinct applications. We ran simulations of Jamaica Bay and the surrounding region including New York Bight and the Hudson River for Hurricane Ida in 2021 as well as several other storm event periods. The model was adapted to represent the combined effects of coastal storm surge along with pluvial flooding from the intense precipitation during Ida. The addition of drainage rates in the watershed was a novel and essential contribution to represent the effects of rainfall and overland flow on coastal flooding. Analysis of model results quantified the increase in flooding associated with the rainfall contribution and tested the sensitivity of flooding to storm track and timing (Kasaei et al. 2025). The coupled model was also used to evaluate the effect of rainfall on the 100-year coastal flood event using a set of realistic scenarios from historical tropical storms. Results showed significant expansion of the flood zone, particularly for certain urban landform types like coastal landfill. The results are presented in a paper that has been accepted for publication (Kasaei et al. 2025).

The other major thread of the study was to examine how sediment transport in Jamaica Bay is affected by storm surge mitigation measures. A storm protection measure that is being actively considered for Jamaica Bay is the construction of storm surge barriers in the entrance channel. Surge barriers would isolate the bay from high water events during major storms but the gates would otherwise remain open to tidal exchange. We used the coupled modeling system to evaluate how the fixed barrier infrastructure in the inlet might impact the tides, salinity conditions, and sediment transport in Jamaica Bay. We developed a high resolution nested grid (~5 m grid spacing) to represent the alterations to the velocity and sediment transport from a surge barrier design proposed by the US Army Corps of Engineers. Fixed infrastructure to house barrier gates would partially obstruct tidal flow through the inlet. As a result, the cross-sectional area open to flow with the barrier decreases to 62% of the original inlet conditions. The constriction accelerates velocities in the inlet, resulting in increased drag due to a form drag and bottom friction. This would decrease the total tidal amplitude in the bay slightly (~1%) and cause a much larger decrease in in the M4 tidal constituent (~10%) that is primarily responsible for the landward sediment transport into the bay.

Sediment supply for Jamaica Bay comes predominantly from tidal exchange with the coastal zone outside the estuary rather than from watershed inputs. Consequently, the decrease in tidal amplitude results in a decrease in sediment import to the bay. Fine sand transport into the estuary is particularly impacted, decreasing by about 20% compared to conditions without the barrier infrastructure. Finer sediments in the medium and fine silt size-classes have more modest reductions in import due to their slower settling velocities. These alterations to sediment transport during typical tidal conditions do not consider any additional impacts to sediment supply by surge barrier closure during storm events. The reductions in sediment supply with the barrier could adversely impact salt marsh resilience and restoration efforts that also protect against storm surge in the bay.

Lead Principal Investigator: David Ralston, Woods Hole Oceanographic Institution

Partner Institution: Woods Hole Oceanographic Institution

Federal Agency: U.S. Geological Survey

Federal Agency Technical Contact: Britt Raubenheimer

Federal Involvement: The project involved close collaboration with colleagues at the USGS Woods Hole who provided expertise in numerical modeling and coastal processes. This included approximately bi-weekly meetings and resulted in several co-authored papers.

Project Type: Research

Start Year: 2022

End Year: 2024

Initial Funding Amount: $200,000.00

Federal Grant Number: G22AC00398

Location: Jamaica Bay, New York

State(s): Massachusetts

Massachusetts Counties: Barnstable

Student and Other Involvement:

• Staff: 1

Summary of Student Involvement: The project included collaboration with and mentoring of a Ph.D. student at Stevens Institute of Technology, but not direct support. The collaboration resulted in two papers that were led by the student.