Structures of Coastal Resilience PHASE 2 DETAILED DESIGN ......demands on coastal structures; second, protection through resilient engineered flood protection and building code requirements;

Structures of Coastal Resilience PHASE 2 DETAILED DESIGN Executive summary 17 June 2014

Executive Summary 1

Table of Contents

01 Introduction 2

02 Background and Objectives 4

03 Local Sea Level Rise Projections 8

04 Hurricane Storm Surge Hazards Assessment 10

05 Geographic Information Systems Flood Mapping 12

06 Narragansett Bay RI Strategies and Design 14

07 Jamaica Bay NY Strategies and Design 17

08 Atlantic City NJ Strategies and Design 21

09 Norfolk VA Strategies and Design 24

10 References 27

2 SCR Phase 2: Detailed Design June 2014

01 Introduction

Structures of Coastal Resilience (SCR) is a Rockefeller Foundation-supported research initiative among four universities and led by Princeton University to assess coastal climate change and storm hazards and propose resilient designs for four coastal urban sites on the North Atlantic coast of the United States. The research incorporates state of the art climate science for local sea level rise estimation and probabilistic hurricane storm surge hazards assessment, and will develop site specific projects highlighting coastal resilience design features, strategies, and frameworks that can be applied throughout the North Atlantic region. The research and design work is proceeding in collaboration with members of the US Army Corps of Engineers’ North Atlantic Division, including their National Planning Center for Coastal Storm Risk Management and the Corps’ Engineer Research and Development Center in Vicksburg, Mississippi.

SCR brings together a distinguished group of engineers, scientists, architects, landscape architects, and scholars, matching an unparalleled depth of design experience with state of the art climate science. The project is overseen and managed by Guy Nordenson and Enrique Ramirez of the Princeton University School of Architecture. The science and engineering team, working on the climate change and probabilistic coastal hurricane storm surge hazards assessment, is also based at Princeton and includes Michael Oppenheimer and Christopher Little of the Woodrow Wilson School of Public and International Affairs, and Ning Lin with Talea Mayo at the Department of Civil and Environmental Engineering. Michael Tantala, a consulting engineer and Geographic Information Systems (GIS) expert, is working with the team to map the extent of flooding and other effects of the calculated storm surges.

The four university-based design teams include the Harvard University Graduate School of Design team led by landscape architects Michael Van Valkenburgh and Rosetta Elkin; the City College of New York Spitzer School of Architecture team led by Catherine Seavitt; the Princeton School of Architecture team led by Paul Lewis; and the University of Pennsylvania School of Design team led by Anuradha Mathur and Dilip da Cunha. Each team is focusing on a specific study area: the Harvard team is developing strategies for Narragansett Bay, Rhode Island that include a close analysis of botanical species and their use as storm surge attenuator, as well as close engagement with local stakeholders. The CCNY Spitzer School of Architecture team is studying ways to address back-bay flooding, sediment nourishment, and water quality at Jamaica Bay, New York. The Princeton University School of Architecture team is creating resiliency schemes for Atlantic City, New Jersey that consider the social and economic history of the region. The University of Pennsylvania School of Design team is examining Norfolk and Hampton Roads, Virginia, specifically the conflux of the James and Elizabeth Rivers, and the effects of storm surge and sea level rise in a region that has been subsiding at an alarming rate.

Executive Summary 3

This interdisciplinary collaboration between architects, landscape architects, engineers, climate scientists, civil engineers, and hydrologists will produce designs, analyses, and recommendations that integrate probabilistic hazards assessment and dynamic performance based designs.

The first phase of SCR began in October 2013 with site, context and coastal flooding vulnerability analyses of the four selected urban coastal areas: Narragansett Bay, Rhode Island; Jamaica Bay, New York; Atlantic City, New Jersey; and the Norfolk and Hampton Roads area, Virginia. Since February 2014 the work has advanced to the second phase, which centers on the development of detailed designs for the four sites. The science and engineering teams at Princeton University have been developing local sea level rise (LSL) predictions for the four sites as well as storm surge projections including the effects of climate change. At the same time, the design teams from Harvard University, City College of NY, Princeton University and University of Pennsylvania continue to refine their designs for the four specific sites. In the third and final phase of the research, these site-specific design projects will be verified by applying the Princeton storm surge flooding assessments.

Figure 1.1: Seaside Heights, New Jersey after Hurricane Sandy, November 2012


Background and Objectives

The extensive damage caused by Hurricane Sandy in October 2012 has heightened public awareness of the vulnerability of urban coastal areas to catastrophic storms, and highlighted how climate change drives rising sea levels and warming oceans to increase the frequency and severity of storms. In light of this, SCR re-examines coastal planning and design so that inhabited coastal regions can be adapted to both the gradual and extreme consequences of these changes in climate and natural hazards.

The objective of SCR is to bring together a state of the art probabilistic assessment of coastal storm surge hazards, including the effects of climate change, together with a new approach to “dynamic performance based design” for coastal resilience using strategies that provide layered protection and adaptability over time.

The methods developed in SCR differ in a number of ways from those of the existing National Flood Insurance Program (NFIP): they emphasize planning for controlled flooding as well as flood control, and they build on the US Army Corps of Engineers’ (USACE) use of natural and nature based features (NNBFs) for storm energy attenuation. Most importantly, a guiding principle of SCR is to assure that the methodologies for dynamic performance based flood resistance design are simple, efficient, and are easily understood and applied.

02

Figure 2.1: Jamaica Bay view of JoCo Marsh, JFK Airport runway, Brooklyn terminal moraine, and Manhattan skyline

Executive Summary 5

Re-evaluating Flood Risk Management and Mitigation The National Flood Insurance Program (NFIP), a mechanism by which the US Federal Emergency and Management Agency (FEMA) promotes storm surge protection and provides financial resources for post-storm recovery, needs to be re-evaluated in light of climate change and its resultant effects on storms. The principle limitations of the NFIP are:

• The program does not consider the effects on storms and flooding of sea level rise and ocean warming due to climate change.

• The FEMA calculations used to create the coastal storm surge flood insurance rate maps (FIRMs) have a number of constraints based on limited historical storm data as well as often out of date and inconsistent information regarding topography and bathymetry, land use, and structural features. This has been the subject of important papers in the recent past, including the National Research Council’s “Mapping the Zone: Improving Flood Map Accuracy” (NRC 2009) and the Jessica Grannis paper “Analysis of How the Flood Insurance Reform Act of 2012 (HR 4348) May Affect State and Local Adaptation Efforts” (Grannis 2012), published by the Georgetown Climate Center.

• NFIP promotes risky development by exempting from the insurance and building code mandates those communities that are in what are known as ‘residual risk areas’ located behind existing flood control structures such as levees and dams. As noted in Grannis (2012) “these properties, however, continue to suffer from “residual risk” because flood control structures often are overtopped or fail—as was demonstrated by the catastrophic failure of the levees protecting New Orleans during hurricane Katrina” (p. 5).

• Political compromises have often lead to reducing flood insurance rates, resulting in an inability of the NFIP to cover the cost of recovery and building.

Although coastal flood resistant hazards mapping has improved in the last few decades, it has not kept up with methodological developments in similar fields such as earthquake and wind hazards mapping. While earthquake and wind hazards maps define zones of varying hazards due to site and other local conditions, they do not designate areas of zero hazard adjacent to areas of severe hazard as is indicated on flood maps. In our view such sharp binary distinctions are not realistic. Flood maps should incorporate the range and uncertainty in hazards and the degrees of contingent risk (such as levee breaching).


Designing for Risk There are many common engineering design practices that incorporate robustness, redundancy and resilience to allow for uncertainties in demands or events. For example, automotive design employs features that absorb and dissipate the energy of collisions and protect occupants if not the vehicle. Buildings that are earthquake or blast-resistant are also designed to absorb energy and save lives while allowing for irreparable damage in extreme events. Similarly wind-resistant building practices consider performance at different thresholds of vibration or damage for frequent and extreme wind storms.

A similar approach can be applied to flood resistant design. We propose combining probabilistic climate and storm hazards assessment with dynamic performance-based design to create flood resistant designs that combine the three functions of: first, attenuation and dissipation of wave energy to reduce the demands on coastal structures; second, protection through resilient engineered flood protection and building code requirements; and third, planning for controlled flooding through urban and flood plain management and design.

Figure 2.2: Atlantic City, New Jersey, South Inlet during the Great Atlantic Hurricane of 1944

Executive Summary 7

Complementing and Improving Prior USACE Work The North Atlantic Coast Comprehensive Study (NACCS) was assigned to the USACE under authority of the Disaster Relief Appropriation Act of 2013. As part of a group of Federal initiatives enacted in the wake of Hurricane Sandy, this “Comp Study” addresses the flood risks of vulnerable coastal populations in the areas that were affected by Hurricane Sandy within the boundaries of the North Atlantic Division of the Corps via the design and deployment of structural, nonstructural, and ‘natural and nature based features’ (NNBFs).

SCR aims to complement the NACCS by providing specific and actionable recommendations for hurricane protection that can result in USACE feasibility studies. The SCR principles of ‘attenuation, protection, and planning’ build on the USACE’s approach of using NNBFs for coastal resilient design, providing engineered or structural protection to prevent flooding, and instituting planning, code and other ‘nonstructural’ requirements. Whereas NNBFs provide ‘attenuation,’ structural features provide both ‘protection’ and ‘attenuation’, and nonstructural measures both ‘plan’ and ‘protect’.

State of the Art Hurricane Storm Modeling SCR is also dedicated to re-evaluating storm modeling techniques. Using methods and studies pioneered by Kerry Emmanuel of MIT and Ning Lin, her team, and collaborators at Princeton University, SCR will use Global Circulation Models (GCMs) to generate thousands of synthetic storms under present and future climate conditions in order to make consistent probabilistic assessments of coastal storm surges that are translated into probabilistic flood maps using Geographic Information Systems (GIS) software. Figure 2.3: USACE natural and

nature based features

Dunes and Beaches

Oyster and Coral Reefs Barrier Islands

Benefits / Processes Break offshore waves Attenuate wave energy Slow inland water transfer

Performance Factors Berm height and width Beach slope Sediment grain size and supply Dune height, crest, width Presence of vegetation


Performance Factors Reef width, elevation and roughness

Vegetated Features: Salt Marshes, Wetlands, Submerged Aquatic Vegetation (SAV)

Benefits / Processes Break offshore waves Attenuate wave energy Slow inland water transfer Increase infiltrationPerformance Factors Marsh, wetland, or SAV elevation and continuity Vegetation type and density

Benefits / Processes Wave attenuation and/or dissipation Sediment stabilization

Performance Factors Island elevation, length, and width Land cover Breach susceptibility Proximity to mainland shore

Maritime Forests/Shrub Communities

Benefits / Processes Wave attenuation and/or dissipation Shoreline erosion stabilization Soil retention

Performance Factors Vegetation height and density Forest dimension Sediment composition Platform elevation

source: http://aquaviews.net

Dunes and Beaches

Oyster and Coral Reefs Barrier Islands


Performance Factors Berm height and width Beach slope Sediment grain size and supply Dune height, crest, width Presence of vegetation


Performance Factors Reef width, elevation and roughness

Vegetated Features: Salt Marshes, Wetlands, Submerged Aquatic Vegetation (SAV)

Benefits / Processes Break offshore waves Attenuate wave energy Slow inland water transfer Increase infiltrationPerformance Factors Marsh, wetland, or SAV elevation and continuity Vegetation type and density

Benefits / Processes Wave attenuation and/or dissipation Sediment stabilization

Performance Factors Island elevation, length, and width Land cover Breach susceptibility Proximity to mainland shore

Maritime Forests/Shrub Communities

Benefits / Processes Wave attenuation and/or dissipation Shoreline erosion stabilization Soil retention

Performance Factors Vegetation height and density Forest dimension Sediment composition Platform elevation

source: http://aquaviews.net


03 Local Sea Level Rise Projections [Michael Oppenheimer and Christopher M. Little]

Methods Local sea level (LSL) projections require the aggregation of the individual components of sea level change including changes in steric and dynamic ocean height, glacier mass balance, ice sheet mass balance, land water storage, and vertical land motion. LSL change differs from global sea level change because of: (1) non-uniform changes in ocean properties and dynamics; (2) changes in the Earth’s gravitational field, rotation and lithospheric flexure associated with the redistribution of mass between the cryosphere and the ocean; and (3) vertical land motion due to glacial isostatic adjustment, tectonics, local groundwater withdrawal, and natural sediment compaction and transport. The design sites considered in this report have experienced long-term rates of LSL rise ranging from 2.5 to 4.3 mm/yr (approximately 50-150% higher than GSL rise) (Figure 3.1).

In this project we utilize projections developed in Kopp et al (submitted), based on climate changes forced by one or two Representative Concentration Pathways (RCPs) (Meinshausen et al 2013). The probability distributions for future LSL change due to each component are informed by climate models, expert assessment, and tide gauge observations, and are combined using a Monte Carlo technique (Figure 3.2).

1880 1920 1960 20000

20

40

60

Jp

Nk

Nb

Ac

0

1

2

NkAc

Jp

Nb

Gl

Lo

cal s

ea le

vel c

hang

e si

nce

1880

(cm

)

Year

Figure 3.1: The historical local sea level record (thin lines) and long-term trends (thick lines, from Kopp 2013) at the closest tide gauges to the four design sites: Norfolk (Nk, black); Atlantic City (Ac, red); Jamaica Bay (Jp, blue); Narragansett Bay (Nb, green). Sea level at each location is shown relative to the value of the smoothed trend in 1880. The global mean trend (from Church and White 2011) is shown in purple. The inset shows long-term linear trends in relative sea level (colors, in mm/yr), for the Eastern United States and Canada. Data and inset map courtesy of Bob Kopp and modified from Kopp (2013)

Executive Summary 9

Results We present projections of GSL and LSL rise at four tide gauge locations in Figure 3.3. The magnitude of sea level change (of any likelihood) at all locations is expected to be far larger over the second half of the century than the first half. Uncertainty also grows over time.

US east coast sea level rise is almost certain to be higher than the global mean over the 21st century, due to ongoing land subsidence and projections of enhanced dynamic sea-level rise in the mid-Atlantic. At the four tide gauges considered here, the median LSL projections in 2100 range from 90-110 cm, substantially higher than the global mean value of 78 cm. High-end (95th percentile) LSL projections (145-165 cm) exhibit a larger divergence from GSL (120 cm) because these low-likelihood outcomes are driven by Antarctic ice loss which has a large “fingerprint” on the east coast. Low-end (5th percentile) projections of LSL range from 40-65 cm, reflecting: (1) very high confidence in at least a continuation of current trends and (2) disparities resulting from spatial variation in subsidence rates.

For design efforts that seek to be robust to lower-probability outcomes, these results suggest that regional differences in LSL rise over the study region may not be as important as the uncertainty in GSL sources that are largely common among the sites. However, we caution that the findings shown in this section apply only to the mean rate of sea level rise and may not indicate trends in flood risk, which will require the combination of these projections of mean sea level with those for storm surge.

Figure 3.3: Observations (to 2011) and preliminary projections (to 2100) of sea level (relative to 2000) for RCP 8.5. Solid lines in the left panel show the historical trend and median projection of local sea level for Norfolk (Sewell’s Point, in black) and the global mean (purple). Shading encompasses 2-sigma uncertainty ranges for observations and 5-95th percentile ranges of relative sea level. The right panel shows median (circles), 17-83rd percentile (thick bars), and 5-95th percentile (thin bars) ranges of local sea level change in 2050 and 2100 for all four sites (colors correspond to those in Figure 3.1)

Figure 3.2: Schematic illustration of the sources of information (red) and physical processes (black) included in the mean sea level projections


Hurricane Storm Surge Hazards Assessment [Ning Lin and Talea L. Mayo]

We are applying the methodology of Lin et al (2012) with the goal of assessing the risk of coastal inundation due to hurricane storm surge at each of the Structures of Coastal Resilience (SCR) project sites. In consideration of the changing climate, we seek to assess the risk for both current and projected climate conditions. Using this methodology, we estimate storm surge return levels by forcing a hydrodynamic model with the wind and pressure field data of thousands of hurricanes (eg Figure 4.1). Rather than relying on limited historical records, we force the hydrodynamic model with synthetic hurricanes (Figure 4.2), which are generated from a statistical-deterministic model (Emmanuel et al 2006). This hurricane model uses large-scale atmospheric and oceanic data as input, which can be generated from global climate models (GCMs). Thus to assess the current risk of storm surge, we use large-scale data of the observed climate as estimated by the NCEP/NCAR reanalysis (Kalnay et al 1996). To assess the risk for projected climate scenarios, we use large-scale data modeled by four GCMs informed by the RCP8.5 emissions scenario from the Intergovernmental Panel on Climate Change fifth assessment report (Stocker et al 2013). In addition to the generation of synthetic storms, we account for climate change through the mean sea level, as hurricane storm surge is modeled relative to this datum. Previous research has shown that the nonlinear effect of higher sea level on storm surge is statistically insignificant (Lin et al 2012), and thus we will account for the projected sea level rise linearly.

04

Figure 4.1: Return levels computed in Lin et al (2012) for the Battery Park in NY

Executive Summary 11

Our work uses the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) hydrodynamic model (Jelesnianski et al 1992). This model is the official operational forecast model of the National Oceanic and Atmospheric Administration. The National Weather Service, the National Hurricane Center, and the Federal Emergency Management Agency also use this model for emergency planning and response. It numerically solves the shallow water equations (SWE) on predefined numerical domains (i.e. basins, Figure 4.3), computing estimates of stillwater elevations at user-specified locations given the wind and pressure fields of an associated hurricane.

The model has several limitations, including the small size and course resolution of the basins, and a wind component that is sometimes highly uncertain (Lin et al 2012). However, the SLOSH model is able to simulate storm surge very quickly with few computational recourses, a prerequisite for the large number of simulations required for our methodology. Additionally, when hindcasting historical storms, we have obtained estimates of storm surge, which compare well with observed data, warranting the use of SLOSH for our risk assessment. In later phases of this research, we will use a higher fidelity hydrodynamic model, the Advanced Circulation model (Luettich et al 1992), to assess the risk at one of the project sites. The ADCIRC model is able to solve the SWE on unstructured meshes, allowing greater numerical resolution in areas of interest. It is also able to compute hurricane wind and pressure fields for a variety of wind models. We will compare the results obtained from the two models to assess the impact of these variables.

Figure 4.2: Hurricane tracks of synthetic storms generated for the NY area

Figure 4.3: SLOSH model numerical domains (i.e. basins)


Geographic Information Systems (GIS) Flood Mapping [Guy Nordenson, Tess McNamara and Michael Tantala]

SCR uses geospatial models to evaluate the effects of flooding in the four study regions. Coastal elevation and bathymetric data were combined using Geographic Information Systems (GIS) software to create a “topobathy” model. Topobathy allows the study of continuous changes in elevation from the seafloor, a method that is especially useful in analyzing the effects of sea level rise and flooding on coastal structures.

The SCR geospatial maps and models were created using the projection system favored by the US Geological Survey (USGS), FEMA, the Department of Homeland Security (DHS), and other agencies. The quarter-quadrangle (QQ) and quarter-quarter quadrangle (QQQ) grid reference systems, which are related to the USGS 7½ minute quadrangle index maps, were then combined with coarse- and fine-grained computational basins from Sea, Lake, and Overland Surges from Hurricanes (SLOSH) models to create a baseline geospatial framework for SCR.

SLOSH already uses topographic data; however it is only updated periodically as new SLOSH basins are released. In this stage of the project, the original SLOSH basins will be used to model synthetic storm tracks, however in the future, the topobathy models produced by SCR will be used in conjunction with hydrodynamic models to more accurately model storm surge. The topobathy models will also be used to create highly-detailed floodplain and inundation maps for use during later stages of the project.

These inundation analyses will complement methods used by FEMA, such as the Flood Rate Insurance Maps (FIRMs) and Wave Height Analysis for Flood Insurance Studies (WHAFIS). However, the SCR maps will include a more extended set of return periods and also map the effects of climate change. Maps will be produced for 100, 500 and 2,500 year return periods and for current climate conditions as of 1980-1999 and estimated future conditions as of 2080-2099 and an intermediate condition at 2050 for a total of nine design performance scenarios. A preliminary set of maps based on Aerts et al (2013) is shown for nine scenarios in Jamaica Bay, NY in Figure 5.1. In this study, local mean sea level rise projections for New York City, developed in Kopp et al (submitted), are used to simulate future climate conditions. The same set of maps is shown in Figure 5.2, including the flood protection measures proposed in A Stronger More Resilient New York (SIRR) by The City of New York (2013) for South Brooklyn and South Queens with the addition of a storm surge barrier across the Rockaway Inlet.

05


Figure 5.1: ADCIRC inundation matrix for Jamaica Bay, NY study region

Figure 5.2: ADCIRC inundation matrix for Jamaica Bay, NY study region, with SIRR intervention


Narragansett Bay RI Strategies and Design Harvard University Graduate School of Design [Michael Van Valkenburgh, Rosetta Elkin, Michael J. Luegering, Marissa Angell]

General Method The Harvard GSD team is focused on developing a set of generalizable storm surge mitigation strategies for what the USACE refers to as natural and nature based features (NNBFs). This research explores the wider potential of NNBFs using the team’s landscape architecture background to explain the potential roles of NNBFs in which vegetation is the primary component. The research confirms two particular consequences of specifying vegetative-NNBFs: a distributed and interdependent approach to site selection, and a scale of design that proposes planting as a potential natural and cultural resource.

This proposal is being supported through conversation and collaboration with local, national and international experts in the fields of ecology and biology. The Harvard GSD team has consulted with Dr. Peter Del Tredici of the Harvard University Arboretum, Dr. Hermann Fritz of Georgia Tech, Grover Fugate of the Coastal Resources Management Council, and Christopher Miller of the NRCS in the course of researching NNBFs. The GSD team’s work suggests that there are several factors, including the quantity, area, species specificity and root depth of vegetation as well as the severity of bathymetric slope preceding the dry land location of a vegetative NNBFs, that have implications for its effectiveness at diminishing the destructive wave action of surges. Further, the development of a specific selection of species is being generated that will characterize the resiliency of particular plants through sprouting, root morphology, and wind firm attributes.

Figure 6.1: Coastal Forest

06


Figure 6.2: Rhode Island Sites


Figure 6.3: Site Conditions

Site-Specific Application Working at a regional scale, the Harvard GSD team is studying both the physical and hydrodynamic conditions of Narragansett Bay to identify locations and conditions in which large stands of vegetation along with minimal and precisely located hardened coastal structures might be able to mitigate wave destruction, slow water, and limit debris movement stemming from hours of surge water conditions. Our hypothesis is that as the severity of these factors increase with sea level rise, the ability of vegetative-NNBFs to grow and change through human management and the natural process of root based accretion of marine substrate will offer several benefits, including: serving as a cost-effective redundancy to coastline protection measures; adding to the life span and effectiveness of traditional coastal structures ranging from the Fox Point Storm Surge Barrier in Providence to coastal revetments in Warren, limiting coastal erosion; as well as providing critical habitat and recreational space.

The Harvard GSD team has chosen three areas of interest representative of three generalizable conditions: Sachuest Point in Lower Bay, The Greater Hummocks in Mid Bay, and Warren in Upper Bay. The socio-economic status of these areas vary from very low to very high as defined by a range of metrics including the Social Vulnerability Index (CDC 2010) and Rhode Island town-specific auditor’s structural replacement assessments. The Hummocks has been designated as the site of a specific project to be more intensely developed, offering the USACE an opportunity to test strategies for adapting to the comprehensive changes that will necessarily accompany a large-scale, distributed NNBF implementation. These strategies will explore possibilities for the protection of infrastructure, the expansion of habitat, the removal of homes, and the planting of attenuation forests as outlined in our proposal.


Jamaica Bay NY Strategies and Design City College of New York, Spitzer School of Architecture [Catherine Seavitt, Kjirsten Alexander, Danae Alessi, Eli Sands]

General Method The City College of New York team approaches Jamaica Bay through an assessment of the history of USACE’s studies as well as by merging ecosystem restoration and natural and nature based features (NNBFs) to achieve coastal storm risk management (CSRM). Our research team has identified a holistic set of strategic recommendations supporting coastal resiliency at Jamaica Bay, inclusive of the Rockaway Peninsula, the central marsh islands, and the tributary inlets at the Bay’s interior perimeter. We also seek to address social, environmental, and infrastructural vulnerability, with the goal of enhancing the overall resiliency of Jamaica Bay.

Because of extensive urbanization, the Bay’s 85,000 acres of historic watershed have been transformed into a constructed sewershed, increasing pollutant delivery and removing sediment input. This continues to be detrimental to Jamaica Bay’s water quality, intertidal marshes, and benthic environment. Addressing poor water quality and sediment starvation is necessary for the sustained performance of any ecological improvements at Jamaica Bay. The vast scale and fetch dimension of the Bay are assets for exploring the performance of NNBFs, particularly salt marshes, as a component of both ecosystem enhancement and storm risk management.

Figure 7.1: (Left) The “island motor” concept uses natural processes to capture sediment through the use of an “atoll terrace” perimeter ridge at the marsh islands (Right) The construction of “atoll terraces” would be aligned with a local dredged material management plan, providing immediate benefits for vulnerable communities and marsh islands

07


Figure 7.3: Jamaica Bay resiliency master plan showing strategic recommendations for the Rockaway Peninsula, the central salt marsh islands, and the Bay’s interior perimeter

Figure 7.2: Merged topographic - bathymetric Digital Elevation Model (DEM) of Jamaica Bay


The Bay would also benefit from the establishment of a local dredged material management plan. By establishing a cyclical schedule of both bay and beach nourishment at Jamaica Bay, material from maintenance dredging may be beneficially reused to nourish coastal beaches, enhance marsh islands, and create living shorelines.

The development of our Jamaica Bay-wide resiliency master plan includes three strategies: first, the improvement of water quality and the reduction of residence time and back-bay flooding via a series of overwash plains, tidal inlets, and flushing tunnels at the Rockaway Peninsula and Floyd Bennett Field; second, the strategic gradient enhancement and elevation of coastal edges at vulnerable back-bay communities to reduce flood risk via a layered system of marsh terraces, berms, and sunken attenuation forests; and third, the development of novel strategies of bay nourishment and salt marsh island restoration through maximizing the effects of the strategic placement of minimal quantities of dredged material. This feature, which we call the “island motor / atoll terrace,” would align with local cycles of maintenance dredging.

Site-Specific Application Salt marsh loss at Jamaica Bay is a paradigmatic example of environmental vulnerability, particularly given the recent acceleration of this loss as well as the implications of future sea level rise. A resilient marsh ecosystem provides coastal storm risk management services to adjacent communities, including the protection of critical transportation infrastructure through wind fetch reduction and wave attenuation during lower return period storm events. After assessing the methods and results of the innovative marsh island restorations at Jamaica Bay undertaken in partnership with the National Park Service, USACE, and local environmental NGOs, we are considering new methodologies of sand placement.

A novel strategy of marsh island restoration, our “island motor” harnesses the strategic placement of minimal quantities of dredged material as a perimeter “atoll terrace,” allowing the natural processes of current-driven sediment capture and deposition to nourish the marsh, thus allowing it to accrete upward with sea level rise. Atoll terraces are arrayed at the perimeter of the marsh island footprints, positioned to best capture sediment given predominant current speeds, tidal flows, and sedimentary transport. The construction of the atoll terraces would be aligned with availability of local dredged material and sequenced to provide maximum immediate benefits for the most vulnerable communities and marsh islands.


The atoll terraces, formed specifically to reduce wave energy and turbidity as well as to encourage deposition, will provide both an ideal slope for the establishment and upward migration of low marsh grasses (Spartina alterniflora) as well as conditions for achieving the water clarity and light penetration required for the successful establishment of submerged aquatic vegetation (Zostera marina). We are also examining resilient plant selections for the marsh islands given climate change, such as ‘submerged aquatic vegetation’ (SAVs) that tolerate warmer waters and low marsh / high marsh / upland species that are adaptive to wetter and warmer climates. Ensuring the future success (and indeed, the continued existence) of the salt marsh islands at Jamaica Bay requires the strategic use of dredged material resources, the improvement of water quality at the Bay, and a robust palette of plant material.

Figure 7.4: The “atoll terraces,” formed specifically to reduce wave energy and encourage sediment deposition, will provide an ideal slope for the establishment and upward migration of low marsh grasses. Reduced turbidity will also improve light penetration, important for the successful establishment of submerged aquatic vegetation


Atlantic City NJ Strategies and Design Princeton University School of Architecture [Paul Lewis, Marc Tsurumaki, David J. Lewis, Kevin Hayes, Anna Knoell]

General Method The Princeton University team has been focusing on the long-term adaptability of back bay communities to rising sea levels and the threat of significant surge from coastal storms. The terms of this debate are often presented as a clear binary of coastal fortification or community retreat, but an array of hybrid solutions is possible. Though fortification can offer hardened protection, it is costly, restricts interaction with the coast, and is vulnerable to overtopping and drainage failures. On the other hand, full retreat of current residents and businesses could allow for accelerated wetland restoration in the back bay and significant decrease in future risk to property and human life, but this strategy has proven to be politically and socially infeasible. Given both personal attachment to home and community and the potentially disastrous flight of tax revenue, retreat is unlikely in the minds of individuals and municipalities.

The Princeton team favors an approach to resiliency which, through intelligent design and careful coordination of non-structural strategies—particularly elevating houses and infrastructure—anticipates rising sea levels and calibrates wetland migration to create a livable future in the back bay of Atlantic City. This amphibious suburb develops a viable alternative to the binary extremes of fortification or retreat, and anticipates continued human settlement by embracing water and the ecological, economic, and resilience benefits of wetlands.

Figure 8.1: Streetscape featuring proposed intervention

08


Figure 8.2: Amphibious suburb


Site-Specific Application The Chelsea Heights neighborhood of Atlantic City offers both specific and generic conditions: it is a former salt marsh hardened by suburban development which remains connected to a greater ecological system between New Jersey’s mainland and numerous barrier islands. Though Chelsea Heights is geographically and historically prototypical of New Jersey’s coast, Atlantic City’s more densely urbanized fabric gives the Princeton team a site where the balance between city and water affects the lives of a more diverse and vulnerable population.

Given that the neighborhood is overwhelmingly residential, we are proposing scenarios phased over a period of 60 years, which attempt to anticipate the behavior of individual residents. Homeowners in low-lying back bay communities are incentivized, by both a desire to avoid flood damage and the threat of increased flood insurance rates, to lift their homes above a designated base flood elevation. A number of others will be likely to abandon their properties. Our recommendation to elevate roads and other vital infrastructure would not only better serve the challenges faced by the existing community, but would also function as protective edges—‘berms with benefits’—throughout the neighborhood. These barriers are strategically designed to allow water to penetrate them at specific points. This controlled permeability in concert with a reduction of hardscape throughout Chelsea Heights would allow for its slow transformation into a true wetland suburb. Canals with living shorelines would replace Chelsea Heights’ redundant back alleys. Local traffic would continue on newly elevated roads with boardwalk access to lifted homes. A renegotiated boundary between private and public land will be guided by the existing principles of rolling easements. In this proposal, the typical suburban expectations of house, lawn, and street are adjusted to welcome the benefits of wetlands and increase the value of the Chelsea Heights.

Figure 8.3: Elevating infrastructure in Atlantic City


Norfolk VA Strategies and Design University of Pennsylvania School of Design [Anuradha Mathur, Dilip da Cunha, Graham Laird Prentice, Caitlin Squier-Roper, Matthew J. Wiener]

General Method The University of Pennsylvania Team has developed an innovative resiliency strategy based on the design potential of a unique natural feature of Tidewater Virginia that they characterize as ‘Fingers of High Ground’ (FHG). FHG meet the sea, river, or creek along their narrower dimension and extend inland between lower grounds. They operate at multiple scales simultaneously. As designed features FHG fit the USACE category of ‘nature based features’ in that they “mimic characteristics of natural features but are created by human design, engineering, and construction to provide specific services such as coastal risk reduction” (USACE 2013, p. 2-3).

Site-Specific Application In the short term, FHG can serve as places of refuge for coastal communities, holding areas of rain that reduce inland flooding, protective barriers, and sites for essential services. In the long term, they can be grounds that change the orientation of settlement designed with ecologically sensitive and economically productive infrastructures and practices, wave attenuators, and habitats for migrating ecologies. Collectively FHG construct a coast that is not a continuous line between land and sea, but a series of discrete and alternating high and low grounds. They protect by accommodating rather than by confronting the rise and fall of rain and tide.

09

Figure 9.1: (Top) Phased inundation in Norfolk through a system of pumps and levees. (Bottom) Development and articulation of FHG


Figure 9.2: FHG offers multiple gradients and possibilites for ecologies and settlement


FHG are particularly suited to a range of ecologies in Tidewater Virginia that operate on gradients vulnerable to sea level rise. FHG allow species migration and plant and animal community adaptation, a process referred to as ‘prestoration.’ The same cannot be said of a system closed by barriers and gates that inhibit such adaptation.

FHG enjoy relative autonomy. They allow for their design and construction to be open to growth, replication, and learning in time. They avoid catastrophic failure that can result from closed systems. Their openness is particularly suited to settlement where people in the face of sea level rise and storm surge are caught between high seas and rain runoff.

FHG offer the opportunity to take immediate incremental actions that will cumulatively address slowly evolving risks. It allows a framework around which local stakeholders can be brought together in the complex task of developing flexible and incremental adaptation strategies that ensure their ability to remain in place despite increasing threat from sea level rise.

The PennDesign Team (in dialogue with local institutions and stakeholders) has developed designs for FHG for Norfolk and Poquoson in particular. They have also investigated the broader applicability of this idea in a number of other areas in Lower Chesapeake including the lower James River, Eastern Shore, areas along the Elizabeth River, and Virginia Beach.

For Norfolk in particular, the PennDesign Team has developed

• The concept of FHG at a city scale as a complement and contrast to a system of barriers, gates, and pumps.

• Design proposals for FHG at Lambert’s Point and Willoughby Spit with guidelines for their incremental development to accommodate shelter-in place, essential services, industry, schools, housing, decentralized water infrastructure, and living shores/piers.

Figure 9.3: (Left) FHG at multiple scales in Tidewater Virginia (Right) Initiating FHG at Lambert’s Point, Norfolk


10 References

Aerts, J., N. Lin, W. Botzen, K. Emanuel, and H. Moel (2013), Low-probability flood risk modeling for New York City, Risk Analysis, DOI: 10.1111/risa.12008.

Bamber, J. L., and W. P. Aspinall (2013), An expert judgement assessment of future sea level rise from the ice sheets, Nature Climate Change, 3, 424–427, doi:10.1038/nclimate1778.

Centers for Disease Control and Prevention (CDC) (2010), Geospatial Research, Analysis, and Services Program, Social Vulnerability Index 2010 Database Rhode Island. http://svi.cdc.gov/SVIDataToolsDownload.html. Accessed on 2014.02.01.

Church, J., and N. White (2011), Sea-level rise from the late 19th to the early 21st century, Surveys in Geophysics, 32(4), DOI: 10.1007/s10712-011-9119-1.

The City of New York (2013), A Stronger More Resilient New York, PlaNYC.

Desbonnet, A., B. Costa-Pierce (Eds.) (2008), Science of Ecosystem-based Management: Narragansett Bay in the 21st Century, Springer Series on Environmental Management, 233-279.

Emanuel, K., S. Ravela, E. Vivant, and C. Risi (2006), A statistical deterministic approach to hurricane risk assessment, Bulletin of the American Meteorological Society, 87(3):299–314.

Grannis, J. (2012), Analysis of How the Flood Insurance Reform Act of 2012 (H.R. 4348) May Affect State and Local Efforts, Georgetown Climate Center.

Horton, R. M., C. Little, V. Gornitz, M.Oppenheimer, D. A. Bader, and C. Rosenzweig (in prep -> submitted), A Framework for Rapid Assessment of Climate Hazards in New York City Post-Hurricane Sandy: Part 2, Sea Level Rise.

Jelesnianski, C. P., J. Chen, and W. A .Shaffer (1992), SLOSH: Sea, lake, and overland surges from hurricanes, US Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service.

Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Saha, G. White, J. Woollen, et al (1996), The ncep/ncar 40-year reanalysis project, Bulletin of the American meteorological Society, 77(3):437–471.

Kopp, R. E., D. J. Rasmussen, C. M. Little, J. X. Mitrovica, M. Oppenheimer, B. H. Strauss and C. Tebaldi (submitted), Probabilistic 21st and 22nd century sea-level rise projections at a global network of tide gauge sites.


Kopp, R. E. (2013), Does the Mid-Atlantic United States sea level acceleration hot spot reflect ocean dynamic variability?, Geophysical Research Letters, 40, 3981–3985, doi: 10.1002/grl.50781.

Lin, N., and D. Chavas (2012), On hurricane parametric wind and applications in storm surge modeling, Journal of Geophysical Research: Atmospheres, (1984-2012), 117(D9).

Lin, N., K. Emanuel, M. Oppenheimer, and E. Vanmarcke (2012), Physically based assessment of hurricane surge threat under climate change, Nature Climate Change, 2(6):462–467.

Luettich, R. A., J. J. Westerink, and N. W. Scheffner (1992), Adcirc: An advanced three-dimensional circulation model for shelves, coasts, and estuaries. report 1. theory and methodology of adcirc-2ddi and adcirc-3dl. Technical report, DTIC Document.

Marzeion, B., A. H. Jarosch, and M. Hofer (2012), Past and future sea-level change from the surface mass balance of glaciers, The Cryosphere, 6, 1295–1322.

Meinshausen, M., S. J. Smith, K. Calvin, J. S. Daniel, M. L. T. Kainuma, J.-F. Lamarque, K. Matsumoto, S. A. Montazka, S. C. B. Raper, K. Riahi, A. Thomson, G. J.M. Velders, and D. P. P. v. Vuuren (2011), The RCP greenhouse gas concentrations and their extensions from 1765 to 2300, Climate Change, 109(1-2), 213-241, doi:10.1007/s10584-011-0156-z.

Milne, G. A., W. R. Gehrels, C. W. Hughes, and M. E. Tamisiea (2009), Identifying the causes of sea-level change. Nature Geoscience 2, 471–478.

National Research Council (NRC) (2009), Mapping the Zone: Improving Flood Map Accuracy, The National Academies Press, Washington, D.C.

National Research Council (2012), Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future, The National Academies Press, Washington, D.C.

Stocker, T. F., D. Qin, and G. K. Platner (2013), Climate change 2013: The physical science basis: working group I contribution to the fifth assessment report of the IPCC, summary for policymakers.

US Army Corps of Engineers (2013), Coastal Risk Reduction and Resilience, CWTS 2013-3, Directorate of Civil Works, US Army Corps of Engineers, Washington DC.

Documents

Structures of Coastal Resilience PHASE 2 DETAILED DESIGN ......demands on coastal structures; second, protection through resilient engineered flood protection and building code requirements;