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Coastal Adaptation Impacts on Water Quality and Flooding

Principal Investigators Philip Orton, Nickitas Georgas, Alan Blumberg, Stevens Institute of Technology; James Fitzpatrick, HDR, Inc.

Funding Agency:  Department of Interior, National Parks Service

Project Period:  November 2014 – October 2016

  1. Summary

Hundreds of thousands of NYC residents in Jamaica Bay’s watershed live on land vulnerable to flooding from a hurricane storm tide. Many types of coastal protective features, ranging from surge barriers to natural features like wetlands and oyster beds, have been suggested as solutions for coastal flooding around the bay. Water quality and storm damage avoidance are integrally linked research topics, as storm protection efforts can harm water quality and alter ecosystems. A project is outlined here to improve upon existing mathematical computer modeling capabilities for Jamaica Bay and to run experiments to study climate change, sea level rise and coastal adaptation impacts on water quality and storm damages. An important part of the project plan is to build Jamaica Bay Science and Resilience Institute consortium technical capacity by making these models available for consortium member use.

View of New York City's skyline, over Jamaica Bay wetlands (credit: Jeanne Hillary)

View of New York City’s skyline, over Jamaica Bay wetlands 

  1. Introduction

Hurricane Sandy was a painful reminder that coastal storms are among the world’s most costly and deadly disasters, capable of causing tens-to-hundreds of billions of dollars in damages and destroying entire neighborhoods. For New York City, hundreds of thousands of NYC residents live at low elevations (below 5 m) surrounding Jamaica Bay, a bay situated on the south-east edge of the city.

Jamaica Bay has an area of 107 km2, is ecologically rich, and has some of the largest remaining tidal wetlands in New York State. However, aerial photographs from 1974 to 1999 show that 2.5 km2 of marshes in the bay’s interior and nearly 80 percent of the interior islands vegetative cover disappeared over this period [Hartig et al., 2002]. The total loss of interior wetlands for the bay since the mid-1800s is estimated to be 12000 of the original 16000 acres [DEP, 2007], and the bay once supported a large oyster fishery producing 700,000 bushels of oysters per year in the early 1900s [Franz, 1982].

Many types of coastal protective features, ranging from surge barriers to natural features like wetlands and oyster beds, are being studied as solutions for coastal flooding. Decisions on which coastal protections to use require detailed studies using computer models that are not available or fully developed for most locations. These models must include many features in addition to physical storm surges, such as chemistry and water quality, to be able to evaluate whether water quality and ecosystems will be harmed by the protections.

Mathematical modeling is useful for understanding water circulation, waves, flooding, water quality, and ecosystem dynamics, among other topics.  Model experiments can reveal dynamics of each of these systems, within the constraints of a given model construct.  Modeling connects with observations, which are used for model development and validation, yet are also interpolated in time and space by the model, to provide a more complete picture a water body, such as Jamaica Bay.  As a result, modeling has major benefits for any comprehensive analysis of the bay, such as for quantification of flood damage reductions.  Modeling also connects with decision analysis, as it opens the door to experimentation to understand future changes due to climate change, sea level rise, and human alterations around and within the bay.

A project is outlined here to improve upon existing modeling capabilities for water quality, flooding and waves for Jamaica Bay, and to run experiments to study climate change, sea level rise and coastal adaptation impacts on water quality and storm damages. An important part of the plan is to build Jamaica Bay Science and Resilience Institute consortium technical capacity by making these models available for consortium member use at CUNY’s High Performance Computing Center (HPCC).

 The primary goals in the project will be to:

  • Improve the existing water quality modeling in Jamaica Bay (J-Bay) with enhanced model representations of wetlands, macro-algae, and wetland and benthic chemical/nutrient fluxes.
  • Improve hydrodynamic model representations of J-Bay wetlands and air-sea interaction
  • Utilize higher-resolution modeling in the bay and improve modeling of exchanges with the coastal ocean by coupling the J-Bay models with inputs from regional scale models
  • Calibrate the improved models using data collected by the consortium and USGS in J-Bay
  • Run experiments to study climate change, sea level rise and coastal adaptation impacts on flooding, waves, water quality and residence time

The two-year project brings together some of the best ocean and water quality modelers from the region, leveraging extensive experience with Jamaica Bay.  It will also include an educational research component and be carried out, in part, by a PhD student and a post-doctoral researcher.

References

DEP (2007), Jamaica Bay Watershed Protection Plan, Volume 1, New York, 128pp pp.

Franz, D. R. (1982), An historical perspective on mollusks in Lower New York Harbor, with emphasis on oysters, Ecological Stress and the New York Bight: Science and Management. Columbia SC: Estuarine Research Federation, 181-197.

Hartig, E. K., V. Gornitz, A. Kolker, F. Mushacke, and D. Fallon (2002), Anthropogenic and climate-change impacts on salt marshes of Jamaica Bay, New York City, Wetlands, 22(1), 71-89.

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Collaborative Climate Adaptation Planning for Urban Coastal Flooding

PIs:  Philip Orton, Alan Blumberg, Peter Rowe (New Jersey Sea Grant Consortium), Tanya Marione-Stanton (Jersey City Department of City Planning); Partners:  Sergey Vinogradov, Naomi Hsu, Steve Eberbach, Jeff Wenger

Funding agency:  NOAA Sea Grant

Project period:  July 2013 – January 2015 (completed)

IMG_5013

Photograph of Philip Orton presenting at City Hall, at one of the public meetings where Jersey City Planners and Stevens Researchers presented options for reducing the chances of storm surge flooding.

Coastal cities across the country are weighing their options for adapting to rising floods, yet there is limited quantitative information available to help make these decisions. This project was a collaboration between coastal flooding scientists and Jersey City planners to develop and test several options for adapting the region’s urban coasts to flooding and sea level rise. Jersey City (JC) is the second-most populous city in NJ, yet has 43% of its land within the new FEMA 100-year flood zones. We leveraged pre-existing storm surge modeling and flood zone mapping to quantify the performance of a set of storm surge protection measures for Jersey City.

Outcomes and outputs from the research included: (1) regional flood zone maps that account for future sea level rise and storm climatology changes, (2) model-based map animations of how floodwaters enter JC to help understand how the pathways can be blocked, (3) a report of a collaboratively determined set of coastal adaptation options, and their performance with sea level rise, (4) an outreach workshop where we presented the project’s results to additional regional stakeholders, and (5) a transferable, peer reviewed and published adaptation planning and evaluation framework. Lastly, and still an ongoing process, it is our goal to help Jersey City, and possibly additional area cities, to implement climate change planning policies to adapt to coastal flooding.

This framework can also be utilized for many other U.S. coastal regions – anywhere that hydrodynamic models are already being used to simulate storm surges or map flood zones. FEMA has embarked on an ambitious effort to re-evaluate the nation’s coastal flood zone maps, and many of these regional efforts are utilizing these models. Many areas also have storm surge forecast models in place that can be similarly used for adaptation studies.

Project Results Summary

Computer storm surge simulations were used to map the effect of projected sea level rise on 100-year flood zones and to show the water pathways that flooded Jersey City during Hurricane Sandy, all useful information for planning measures that can prevent flooding.

Animation of modeled Hurricane Sandy flooding entering downtown Jersey City

Street-valley resolving animation of modeled Hurricane Sandy flooding entering downtown Jersey City (Blumberg et al. submitted). Color shading indicates floodwater depths over ground (legend on bottom right).

In several collaborative meetings, a broad set of realistic coastal protection measures and broad strategies were developed. Here is one example, a surge barrier that helps block a storm surge but could also be closed at low tide to create a rainwater basin for helping reduce the more frequent problem of rainfall flooding at high tide.

Illustration of one of 27 flood protection components, a surge barrier at the Tidewater Basin, south of downtown Jersey City

Illustration of one of 27 flood protection components, a surge barrier at Morris Canal Basin (aka Tidewater Basin), south of downtown Jersey City

This image comes from a partner project by Michael Baker Jr. Inc, and the report for that project is available here and includes both visualizations of the adaptation strategies, as well as a scoping study of what would be needed to conduct a benefit-cost analysis for the plans.

The storm surge modeling was then used to evaluate the efficacy of each adaptation measure, as well as how sea level rise and climate change will affect performance.  A city-wide adaptation scenario that combines several of the individual adaptation measures is found to protect most areas of the city from all storm events tested, ranging from a severe nor’easter that occurred in 1992, to Hurricane Sandy plus 31” of sea level rise (a high-end projection for 2055).

figure_SC4_success

Flood elevation model results for Hurricane Sandy Control (left), the full adaptation scenario (center), and the difference. In the right‐side panel, white areas have flooding in the control run, and do not have flooding with the adaptation scenario (flooding is prevented).

Hurricanes of a higher flood level than Sandy are possible, though unlikely – based on our replication of the FEMA flood mapping study (with added sea level rise), the 14-foot protection elevation could be overtopped by storms today, with an annual probability of 0.3%, or by storms after 31” of sea level rise, with an annual probability of 1%. A partial adaptation plan of land elevation increases around planned projects leads to prevention of flooding for most neighborhoods for the #2 and #3 largest flood events of the past century, the 1992 nor’easter and Hurricane Donna, but does not provide protection against Hurricane Sandy, and only keeps certain neighborhoods dry for the other flood events (e.g. Donna) when we consider 31” of sea level rise.

Read the full report here.

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