Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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COASTAL CLIMATE RESILIENCE Designing for Flood Risk
TM
This study was funded through
a U.S. Department of Housing
and Urban Development (HUD)
Sustainable Communities
Regional Planning Grant to the
New York - Connecticut Sustain-
able Communities Consortium.
NEW YORK & CONNECTICUT
SUSTAINABLE COMMUNITIES
Cover design by Jeffrey Shumaker and Jesse Levin
COASTAL CLIMATE RESILIENCE
Designing for Flood Risk
THE CITY OF NEW YORK
MICHAEL R. BLOOMBERG, MAYOR
DEPARTMENT OF CITY PLANNING
AMANDA M. BURDEN, FAICP, COMMISSIONER
JUNE 2013
www.nyc.gov/designingforfloodrisk
Foreword by the Commissioner
New York is and will always be a waterfront city. At 520 miles, New York City’s wa-
terfront is the longest and most diverse of any city in the United States. This unique
coastal geography is one the city’s major assets but also poses particular challeng-
es for the built environment, particularly in an era of ever-increasing climate risks.
The character of our streets, our neighborhoods and our public spaces is influ-
enced by the character of the buildings at their edges. Designing for Flood Risk
focuses on preparing buildings to withstand the threat of coastal flooding, while
ensuring that they support everyday livability and quality of life. The devastation
in waterfront communities brought by Hurricane Sandy has brought a new level of
urgency to this work. The expansion of the FEMA flood zones and changes to the
National Flood Insurance Program have made the demand to rebuild and retrofit
properties both extensive and immediate. How can we ensure that buildings meet
these higher flood protection standards while preserving the vitality of our neigh-
borhoods?
To meet these challenges, reconstruction must be shaped by clear and tested
design principles. Designing for Flood Risk is the first comprehensive design guide
to address this challenge. It accompanies the recently introduced Flood Resilience
Zoning Text Amendment, and its companion report for the New York-Connecticut
Sustainable Communities Consortium on Urban Waterfront Adaptive Strategies.
Together, this body of work presents a road map for supporting existing communi-
ties and providing for a sustainable future in our waterfront neighborhoods.
Designing for Flood Risk is the product of an intensive collaboration between City
Planning and the architectural and design community. On behalf of the Department
and the City of New York, I want to thank the New York chapter of the American
Institute of Architects and all the individuals and groups that have donated their
time and expertise to craft solutions to both protect the city and continue to enliv-
en it. The principles outlined in this report can be used to guide both public- and
private-sector efforts to rebuild following Hurricane Sandy in New York City, the
broader region, and in other urban coastal communities. Continued close collab-
oration between government and the design community will be critical to address
the many design challenges presented by the need for flood-resilient buildings in a
dense urban context.
Amanda M. Burden, FAICP
Director, Department of City Planning
Chair, New York City Planning Commission
4 NYC DEPARTMENT OF CITY PLANNING
Foreword by the AIA New York Executive Director
The New York Chapter of the American Institute of Architects commends the NYC
Department of City Planning for the publication of Designing for Flood Risk. The
cogent and concise document spells out principles and recommendations, in the
aftermath of Hurricane Sandy, that make sense for any coastal community facing
the vulnerabilities caused by sea level rise and the risk of storm surge. Ideas in the
book, based on the New York region’s experience during the 2012 storm “inform
efforts to create vibrant, active, and resilient neighborhoods everywhere.”
While Sandy was a wake-up call for many, City Planning was already deeply
engaged in risk assessment and design strategies to create flood-resistant struc-
tures. A half-day professional “Freeboard Charrette” took place in March of 2012,
sponsored by the Department and the AIANY Design for Risk and Reconstruction
Committee. Its transdisciplinary findings are summarized in the Flood Risk doc-
ument and anticipate the research, analysis, and recommendations delineated in
more detail throughout the report.
The “range of strategies and mechanisms” needed to promote more resilient
coastal communities will not be easy to achieve all at once. But with this roadmap
to a more resilient future, the City Planning Department, led by its inimitable Chair,
Amanda Burden, has gone a long way to chart the way.
Rick Bell, FAIA
Executive Director, AIA New York
DESIGNING FOR FLOOD RISK 5
ABOUT THE STUDY The New York City Department of City Planning (DCP), funded through the New York-Connecticut Sustainable Communities Consortium under a U.S. De- partment of Housing and Urban Development (HUD) Regional Planning Grant, is examining strategies for making buildings more resilient to the effects of climate change, in particular flooding. As part of this work, DCP has undertak- en this study of the urban design implications of building-scale flood protection standards on neighborhoods within coastal areas. Also under this grant, DCP’s Urban Waterfront Adaptive Strategies study will identify and evaluate potential adaptation strategies at different scales for resilience to coastal flooding in urban coastal communities. 6 NYC DEPARTMENT OF CITY PLANNING
TABLE OF CONTENTS
Introduction Page 8
Flood Resilient Construction Page 12
Design Charrettes Page 20
Urban Design Principles Page 24
Recommendations Page 32
Summary of Conclusions Page 38
Glossary Page 40
References Page 42
Acknowledgments Page 44
DESIGNING FOR FLOOD RISK 7
Power outage in Lower Manhattan after Hurricane Sandy
INTRODUCTION
Climate Resilience and Nor’easters. Currently about 218,000
Coastal Flooding New Yorkers live within the effective
in New York City Federal Emergency Management
Agency (FEMA)-designated 100-year
From its very beginnings, New York floodplain, and FEMA preliminary work
City has been a waterfront city. Its 520 maps released in June 2013 have
miles of diverse coastline are one of more than doubled this figure.
its greatest assets, home to vibrant On October 29, 2012, Hurricane
neighborhoods with tens of thousands Sandy made landfall south and west of
of homes and businesses, as well the city, bringing with it a record-break-
as maritime activities, natural areas, ing storm surge that flooded large por-
and recreational facilities. The city’s tions of the city which brought severe
waterfront geography also means that damage to coastal neighborhoods.
it faces significant coastal flood risks This occurred just over a year after
from tropical storms, hurricanes, and Tropical Storm Irene brought heavy
8 INTRODUCTION
Hurricane Sandy damage in Brooklyn
rains, flooding, and the first emergen- to better manage coastal flood risks.
cy shutdown of the entire New York The city’s building code requires that
City subway system. Hurricane Sandy new buildings in the FEMA-designated
was the most damaging storm in the flood zone elevate or floodproof occu-
city’s history, but because of climate pied space below the FEMA-designat-
change and sea level rise, the city’s ed flood elevation. To increase flood
risks from the most intense hurricanes protection, the building code requires
and coastal flooding are expected to further raising this elevation by one or
increase. The New York City Panel two feet—a practice known as adding
on Climate Change (NPCC), a group “freeboard.” Use of freeboard provides
of climate scientists and risk man- an added margin of safety for address-
agement experts first convened by ing the uncertainties of flood modeling
Mayor Bloomberg in 2008, projects and potential changes, such as sea
that the city’s sea levels could rise by level rise.
more than two feet by the 2050s, and However, elevating buildings also
that the most intense hurricanes are poses challenges to maintaining a
likely to become more frequent. Sea vibrant public realm. Elevated ground
level rise will increase the size of the floors can detract from the quality of
city’s flood zones, putting new areas pedestrian experience and character
at risk of coastal flooding, and leading of neighborhoods by losing visual
to greater impacts in areas already at connectivity with the street, creating
risk. voids or awkward access elements, or
While it may be impossible to elim- deviating from characteristic patterns.
inate all risks associated with coastal New York City’s public realm is inte-
flooding and storms, the City can gral to the city’s economic and cultural
plan for these risks and become more vitality, making it a place that people
resilient – better able to withstand want to live, work, and play. The inter-
and recover from extreme events action among construction codes, the
and environmental changes. A key New York City Zoning Resolution, and
element of these resilience efforts will the work of individual architects and
be ensuring that buildings in the flood designers critically shapes the rela-
zone are constructed and retrofitted tionship between individual buildings
DESIGNING FOR FLOOD RISK 9
FEMA SPECIAL FLOOD HAZARD ZONES IN NEW YORK CITY
VE
COASTAL A
AE
FEMA, Preliminary Work Maps 2013
and the public realm to create a vi- and substantially improved buildings.
brant streetscape environment. Efforts Based on this analysis, the report
to increase the resilience of buildings then identifies certain zoning rules
must be accomplished in a way that that may create challenges for build-
maintains and enhances the quality ing and retrofitting of flood-resistant
of the public realm, by using the best buildings in vulnerable areas. Finally,
tools available to influence the built it describes proposed changes to the
environment. Zoning Resolution that could make the
construction of flood-resistant build-
ings not only more practical, but also
Purpose of this Study supportive of neighborhood character
and a vibrant public realm.
The purpose of this study is to While this analysis focuses on New
identify urban design principles to York City and its regulations, the
guide new construction that adheres issues and strategies identified here
to flood protection standards, as well have relevance to other dense, urban
recommendations for how zoning can environments as well. Most flood-
incorporate these principles. zone construction in the United States
This report begins by providing occurs in lower density areas, and
background on the regulatory context FEMA publications and guidance tend
for flood-resilient design under the to focus on the building types common
National Flood Insurance Program. in these areas, such as single-family
It then describes the urban design construction. With its density and va-
impacts of resiliency standards using riety of building types, New York City
a set of urban design principles and requires a more wide-ranging analysis
common parameters, such as building and a diverse set of strategies for inte-
typology and expected flood eleva- grating flood resilience into the neigh-
tion. The report explores desirable borhoods and buildings of the city.
design solutions for new construction These same analyses and strategies
10 INTRODUCTIONHurricane Sandy damage in Queens
Hurricane Sandy damage in Staten Island
will be applicable elsewhere within region. Because much of the regional
the metropolitan region, particularly transportation network is located near
in areas with denser, transit-oriented the coastline, many opportunities for
development patterns. The activities sustainable growth in the region will
of the New York-Connecticut Sustain- need to incorporate flood-resistant
able Communities Consortium include construction measures. The principles
numerous place-based projects to outlined in this study can inform these
promote transit-oriented development efforts to create vibrant, active, and
within urban centers throughout the resilient neighborhoods.
DESIGNING FOR FLOOD RISK 11Battery Park City along the Hudson River
FLOOD RESILIENT CONSTRUCTION
The Importance of Codes standards require buildings to incorpo-
to Coastal Resilience rate flood-resistant techniques below
the Base Flood Elevation (BFE), the
As both sound policy to protect anticipated height of floodwaters in
life and property and condition of a storm that has a 1-percent annual
the City’s participation in the Na- chance of occurring.
tional Flood Insurance Program The area inundated by Hurricane
(NFIP), the New York City Building Sandy extended beyond the current
Code includes requirements for flood FEMA-designated flood zone and
resistant construction for new and above its flood elevations. While thou-
substantially improved buildings in sands of buildings suffered flooding
FEMA-designated flood zones. These during the storm, newer buildings con-
12 FLOOD RESILIENT CONSTRUCTIONstructed to more recent code require- communities to manage and enforce
ments fared better, demonstrating that requirements within their designated
these requirements are an effective flood zones.
tool for flood protection. Most con- Coastal FISs determine mean water
struction in coastal areas in New York levels and wave elevation for the Spe-
City predates flood-resistant construc- cial Flood Hazard Areas (SFHA), de-
tion standards. Approximately 84% of fined as the land in the floodplain sub-
the buildings within Hurricane Sandy’s ject to a 1-percent or greater chance of
inundation area were built before flooding in any given year. This area is
1983, when the first Flood Insurance also known as the “base floodplain” or
Rate Maps (FIRMs) were issued for “100-year floodplain.” The flood hazard
the city. These buildings are unlikely for each area is determined based on
to have been constructed above flood statistical analysis of historical tides,
elevations or using flood resistant also taking into account characteristics
construction techniques, and often of the adjacent water body, potential
have other features like basements erosion, topography and bathymetry of
or cellars that expose them to higher the floodplain. Storm surge and wave
risks today. The vast majority of build- models are implemented to determine
ings destroyed by the storm (98%) or the BFE.
severely structurally damaged (94%) FIRMs specify the limits of the
were built before 1983. SFHA, which is divided into two sepa-
rate insurance zone designations: “A”
and “V.” These are generally referred
Flood Hazard Zones to as flood zones (see Figure 01),
and are accompanied by BFE con-
To identify and understand the tours. The specific zone designations
flood risk and vulnerability of coastal describe the extent and severity of the
communities within the NFIP, FEMA coastal flood hazard.
conducts hazard studies published as ”V Zone” is a portion of the SFHA
Flood Insurance Studies (FISs) and directly along the coast. This area is
Flood Insurance Rate Maps (FIRMs). subject to inundation by the 1% annual
These documents provide the neces- chance flood event with the added
sary information for the participating hazard of high-velocity wave action,
THE EDGE, WILLIAMSBURG AVERNE BY THE SEA, THE ROCKAWAYS IKEA, RED HOOK
BROOKLYN QUEENS BROOKLYN
Examples of recent developments that suffered little damage during Hurricane Sandy
DESIGNING FOR FLOOD RISK 13with a projected wave height of 3 feet but also introduce a new area defined
or more. as the “Coastal A Zone,” designat-
An “A Zone” is located either inland ed by a boundary called the Limit of
of a V Zone or adjacent to open water Moderate Wave Action (LiMWA). This
where no V Zones are mapped. This zone is the portion of an A Zone where
area is subject to the same 1% annual moderate wave action with projected
WAVE HEIGHT
WAVE HEIGHT
3 - 1.5 ft
over 3 ft
COASTAL A-ZONE FUTURE A-ZONE
V-ZONE A-ZONE B/X-ZONE
100 YR FLOODPLAIN 500 YR FLOODPLAIN
Area that has 1% chance of flooding on any given year Area that has 0.2% chance of flooding on any given year
* New flood zone designation within the existing A-Zone where wave action is experienced.
Figure 01. FEMA FIRMs designations
COASTAL-A ZONES are not mapped in current FIRMs but will be introduced in future revisions by FEMA
chance of inundation as a V Zone, but wave heights between 1.5 and 3 feet
without wave action from waves of 3 is expected during the base flood
feet or more. FIRMs specify the water event. No design and construction
level expected during the flood event, specifications are yet prescribed within
or BFE, for both A and V Zones. the NFIP for Coastal A Zones; howev-
FIRMs are revised and updated er, FEMA encourages jurisdictions to
when new coastal FISs are available. apply more precautionary standards
The FEMA preliminary work maps in such areas, and requirements are
(2013) for New York City show not only being incorporated in model building
updated boundaries of V and A zones, codes.
THE NATIONAL FLOOD INSURANCE PROGRAM
FEMA administers the National Flood Insurance Program (NFIP),
through which private properties’ flood losses are covered by
insurance premiums paid by property owners. New or substantially
improved buildings in the 100-year flood zone are required to main-
tain flood insurance to obtain loans from federally insured banks,
as well as to be eligible for federal disaster assistance. At the same
time, coastal communities participating in the NFIP are required to
match their local codes with FEMA’s requirements. FEMA reports
that, as of May 2011, over 20,000 communities in coastal areas are
participating in the NFIP, including New York City.
14 FLOOD RESILIENT CONSTRUCTIONElevated home in Breezy Point, Queens
Beyond the 100-year floodplain and the elevation of the building site, it
therefore outside the SFHA, FIRMs is necessary to elevate or floodproof
show the area subject to a 0.2% annu- (where permitted) the first occupiable
al chance of inundation during a flood floor to ensure that buildings remain
event, also known as the 500-year structurally sound and to protect build-
floodplain. The base flood elevation ing contents during the flood event.
for this area is not identified on the Freeboard provides an added
FIRMs, though it is provided in the margin of safety, usually expressed
FIS, and there are no design require- in feet above a flood level, to address
ments specified by the NFIP for this the uncertainties of flood modeling
zone. and often compensates for the many
unknown factors that could contribute
to flood heights, including sea level
Flood Resistant Building rise. The NYC Building Code defines
Design the Design Flood Elevation (DFE) as
the BFE plus the designated amount
Consistent with FEMA requirements, of freeboard. (See Figure 02) On
the New York City Building Code January 31, 2013, the Commissioner
establishes minimum structural and of Buildings issued an emergency rule
programmatic requirements for all new to require one or two feet of freeboard
and substantially improved buildings (depending on the building category)
in SFHAs, with requirements based on for buildings in the flood zones.
specific zones within the SFHA. In general, all mechanical equipment
The BFE designated on FEMA flood from electrical, heating, ventilation,
maps serves as the standard to which plumbing and air conditioning systems
flood-resistant construction require- must be located above the DFE or
ments apply. Where the BFE exceeds designed to prevent water from enter-
DESIGNING FOR FLOOD RISK 15A-ZONE V-ZONE
Category I
Structures that represent
a low hazard to human DFE BFE DFE BFE
life in the event of failure
(e.g. storage)
Category II
(1-2 family homes)
DFE BFE + 2 DFE BFE + 2
BFE BFE
Category II
all others
(e.g. apartment building)
BFE + 1 DFE PERP BFE + 1
DFE
BFE DFE PAR BFE
Category III
Structures that represent
a substantial hazard to
human life in the event of DFE PERP BFE + 2 V-Zone: All
DFE BFE + 1 DFE PAR BFE + 1
failure (e.g. secondary BFE BFE
UTILITIES/ATTENDANT
EQUIPMENT required to be
school facilities) placed above DFE + 1. All
FLOOD DAMAGE RESISTANT
MATERIALS to be used
below DFE + 1.
+ A-Zone: min elevation
of FLOODPRROFING to
+
be at BFE + 2
Category IV
Structures designed as
essential (and emergency)
facilities (e.g. hospital)
DFE BFE + 2 DFE PERP BFE + 2
DFE PAR BFE + 1
BFE BFE
BFE: base flood elevation DFE PERP: Lowest horizontal DFE PAR: Lowest horizontal All UTILITIES/ATTENDANT EQUIP-
DFE: design flood elevation, or structural member perpendicu- structural member parallel to the MENT to be placed above DFE and
base flood elevation with lar to the direction of the wave direction of the wave flood demage resistant MATERIALS to
freeboard be used below the DFE;
FLOODPROOFING (wet or dry) to
extend for a minimum elevation of
BFE+1, if not otherwise noted.
Figure 02. Minimum elevation requirements for buildings in flood zones by structure occupancy category - NYC Building Code 2008
16 FLOOD RESILIENT CONSTRUCTIONA ZONE V ZONE
DRY FLOODPROOFING WET FLOODPROOFING ELEVATED STRUCTURE
FLOOD PROTECTION
WATERTIGHT STRUCTURE WATER TO RUN-IN / RUN-OUT VIRTUALLY OPEN STRUCTURE
STRATEGY
e.g. FLOOD SHIELDS e.g. FLOOD VENTS e.g. OPEN LATTICE
FLOOD SHIELDS 1 INCH OF NET OPEN OPEN
PREVENT WATER AREA PER 1 SQ. FT. STRUCTURE
FROM ENTERING OF ENCLOSED AREA
DFE DFE DFE
GROUND FLOOR BFE BFE BFE
CONFIGURATION
1’ MAX
NON-RESIDENTIAL VERTICAL
SPACE FOUNDATION MEMBER
LOWEST OCCUPIED FLOOR LOWEST OCCUPIED FLOOR BOTTOM OF LOWEST
ALLOWED TO BE EXCAVATED TO BE AT OR ABOVE DESIGN STRUCTURAL MEMBER
BELOW GRADE FLOOD ELEVATION TO BE AT OR ABOVE
NOT PERMITTED FOR DESIGN FLOOD ELEVATION
ENTIRELY RESIDENTIAL
BUILDINGS
PARKING PARKING PARKING
PERMITTED USE ACCESS ACCESS ACCESS
BELOW DFE
STORAGE STORAGE STORAGE
NON-RESIDENTIAL NON-RESIDENTIAL NON-RESIDENTIAL
RESIDENTIAL RESIDENTIAL RESIDENTIAL
Figure 03. Design and Construction requirements for buildings in the SFHAs
ing. Below the projected flood levels, dry-floodproofed structure can be at
flood damage-resistant materials are an elevation below grade or below
required (Some variations apply - See the base flood elevation. Through dry
figure 02). Uses below the lowest oc- floodproofing, building access can be
cupiable floor are limited by the NFIP. maintained at grade with no apparent
Parking, minor storage and building differences from a non-floodproofed
access are the only uses allowed condition. Any of these conditions will
below the DFE, except for dry-flood- generally entail higher construction
proofed non-residential spaces, as costs. Dry floodproofing can present
described later. No dwelling units can safety hazards during a flood event by
be located below the DFE. blocking egress, so it is not allowed in
There are two basic techniques of entirely residential buildings.
floodproofing allowed under FEMA Wet floodproofing allows build-
standards: dry floodproofing and wet ings in the A Zone to be designed to
floodproofing. Both techniques could allow floodwaters to enter and leave
be used in A Zones, depending on the the structure without the use of any
building use. (See Figure 03) mechanical equipment. Spaces that
Dry floodproofing makes a struc- are below grade on all sides are
ture watertight up to at least the level prohibited, and the lowest occupiable
of the DFE through the implementation floor is required to be elevated above
of a sealant, flood shields, aquarium the BFE. To prevent the collapse of
glass, strengthening structural com- building walls, a wet-floodproofed
ponents to resist hydrostatic forces building allows for the equalization
from floodwaters, and protecting of hydrostatic forces on both sides of
utilities from flood damage. Unlike the wall during a flood event. This is
wet floodproofing, the first floor of a achieved with openings at the ground
DESIGNING FOR FLOOD RISK 17Recent waterfront development in Williamsburg, Brooklyn
floor that allow water to flow in and buildings, the bottom of the lowest
out at an appropriate rate. Openings horizontal structural member must be
should be provided on at least two elevated above the DFE. Below the
sides of the enclosed space and the DFE, the structure has to be largely
bottom of each opening should not be open, and walls of enclosures must
more than 1 foot above grade level. be designed to collapse under the
Non-engineered openings need to pro- flood loads (breakaway walls). The
vide at least 1 square inch of net open New York City Building Code requires
area for each square foot of enclosed enclosures to be of an open-lattice
space. Engineered openings are type and not solid. Excavation below
required to be certified by a registered grade and the use of structural fill are
professional and designed accord- not allowed in a V Zone.
ing to specific provisions. Buildings
must also use flood damage-resistant
materials up to a level one inch above
the DFE. Land Use and Buildings
As a fairly common practice in New in New York City’s
York City, new mixed-use buildings Flood Zones
in A zones have combined wet and
dry floodproofed areas at the ground Every portion of New York City’s 520
floor. With this solution, portions of the miles of shoreline is mapped within
building are sealed at the ground floor a flood zone, though the distance
to keep floodwaters out, while lobbies these flood zones extend inland varies
and entryways are designed to accom- depending on topography and other
modate flooding. factors.
In V Zones, more stringent stan- The vast majority of New York
dards apply to prevent the damaging City’s 100-year flood plain lies within
force of waves from being transmit- A zones. V zones are limited in New
ted to the structure of the building. York City, found only on the most
For new or substantially improved exposed coastal reaches, including
18 FLOOD RESILIENT CONSTRUCTIONbeaches on the Rockaways, Coney and an additional 16% in commercial/
Island, Staten Island and on Long office buildings.
Island Sound. In New York City there are approx-
Nationally, the overwhelming majori- imately 400,000 residents, 340,000
ty of buildings in flood zones are small jobs, and more than 16,000 compa-
homes. In New York City, too, most nies within the FEMA Preliminary Work
buildings in flood zones are one- or Maps’ 100-year floodplain.** With
two-family homes. However, multi-sto- projected sea level rise, the number
ry buildings make up the largest per- of residents and businesses affected
centage of built area (square footage) by the risk of coastal flooding will in-
in New York City’s coastal area. While crease substantially. Addressing these
73% of the buildings within flood zones risks, while maintaining the vitality and
in New York City are one-and two-fam- diversity of uses in the city’s coastal
ily residential buildings, 35% of floor neighborhoods is a central focus of the
area is within multi-family buildings, city’s climate resilience planning.
50,000 48,591
40,000 48,591
50,000
of Buildings
30,000
40,000
of Buildings
NumberNumber
20,000
30,000
10,000
20,000 7,221
2,348 1,905 1,967 1,364 1,387
1,072 685 6 391
10,0000
7,221
2,348 1,905 1,967 1,364 1,387
1,072 685 6 391
0
Figure 04. Number of buildings in the 100-year flood zone in New York City by land use
120
102M
Square Feet
100
120 76.5M 82M 70.6M
80 102M
ofFeet
100 53.4M 54M
60
76.5M 82M 70.6M
80 37.2M
of Square
40 25.2M
Millions Millions
53.4M 54M
60
20
37.2M 4.7M 0.83M 2.7M
40 25.2M
0
20
4.7M 0.83M 2.7M
0
Figure 05. Amount of floor area in the 100-year flood zone in New York City by land use
*Data provided in this section based on FEMA Preliminary Work Maps (2013) and DCP MapPluto 12v2.
**NYS DOL, 2010 Q3 QCEW. The data reflect firms whose addresses fall within the flood zones and their employees, and the
proportion of jobs allocated to Census Tracts within those flood zones for records that could not be assigned to a specific address.
DESIGNING FOR FLOOD RISK 19DESIGN CHARRETTE / pre-Sandy
On March 23, 2012, the Design for Risk and Reconstruc-
tion Committee of the American institute of Architects (AIA)
New York Chapter and the Department of City Planning
co-hosted a half-day professional charrette exploring de-
sign strategies for flood resistant buildings in New York City.
The charrette took place at AIANY’s Center for Architecture,
and was attended by about fifty leading members of the de-
sign community as well as representatives of City Planning,
Department of Buildings, and the Mayor’s Office of Long
Term Planning and Sustainability.
After a brief presentation on current regulations that gov-
ern building in the flood plain, the participants formed eight
teams. Each team investigated a scenario in which a hypo-
thetical new building must adapt to a high flood elevation.
DCP provided detailed underlay drawings showing context,
topography, infrastructure, and flood elevation. The teams
worked iteratively through a design process, using hand
drawing, and considering a full spectrum of issues including
streetscape continuity, accessibility, drainage, structural
requirements, and land use program.
Participants outlined a wide range of creative design strat-
egies during the charrette. The most prominent recurring
theme was the need to create a vibrant, attractive environ-
ment while satisfying all applicable safety standards.
All of the teams grappled with how the buildings inter-
faced with the public realm. Some of the teams developed
design strategies for creating spaces below buildings that
would be open to the elements per flood regulations, but
also attractive and inviting elements of the streetscape.
Acknowledging that an inviting space below buildings is
difficult to create with a low ceiling and limited access to
daylight, some teams sculpted the building mass to allow
greater solar access to these open spaces.
A second idea that was explored through the charrette
was the potential use of temporary program in areas below
the flood elevation, such as pop-up retail or community
facilities, which could be enclosed in a mobile structure.
20 DESIGN CHARRETTEMARCH 2012
Building access requirements also posed a significant
constraint on the designers. All the sites except the one-
and two-family homes required ADA access. The required
ramps not only consumed large amounts of floor space,
but were also a prominent element of the building’s façade.
This prompted some to emphasize the circulation elements
as virtuous element of the design, a semi-public entryway
to the building’s first occupied floor.
Another recurring theme throughout the charrette was
that flood protection may not be easily addressed at the
building scale, particularly where flood elevations are sub-
stantially above grade. Interventions at a larger scale, such
as seawalls, levees, or surge barriers may offer less disrup-
tive and more economical means of reducing flood risk.
Several teams also sought to explore neighborhood-scale
strategies that fall in between the scale of the individual
property and that of larger infrastructure.
A common suggestion was to raise streets and infra-
structure, which would require a long-term coordinated
investment and effort among property owners and public
agencies.
To avoid the lengthy coordinated reconstruction of all ad-
jacent structures that would be required to elevate a street,
one team proposed to put public pedestrian circulation in-
board of the block, in effect inverting the public and private
faces of every building on the street.
There was a clear, broad consensus among the partici-
pants that this charrette opened an important conversation
about designing for future floods while maintaining high
quality urban design. Many hoped that this conversa-
tion could continue at a wider scale and engage broader
questions about infrastructure and neighborhood-scale
flood protection strategies. While many broader questions
about design for flood resilience remained unanswered,
the principles to which charrette participants adhered were
used to shape the urban design principles that have guided
subsequent work.
DESIGNING FOR FLOOD RISK 21DESIGN CHARRETTE / post-Sandy
On February 23, 2013, the Post Sandy Task Force orga-
nized by the AIA New York Chapter hosted a second pro-
fessional charrette to examine housing design and zoning
issues in the wake of Hurricane Sandy. The workshop was
held at the Center for Architecture, and brought togeth-
er architects, structural engineers, landscape architects,
and representatives from the Department of Buildings,
the Office of Emergency Management, the Mayor’s Office
and FEMA. DCP provided technical assistance before and
during the event.
Participants were divided into six teams, each looking at
different building types representative of the diverse urban
environment of New York City. Teams explored solutions to
either retrofit or rebuild to higher flood protection standards
the assigned typology while considering implications on
massing, integration of building access, and the effects of
the new design on the creation of quality streetscape, while
overall ensuring compliance with flood resilience standards.
While all participants tried to incorporate the flood resil-
ience standards, several proposals highlighted the need for
a more flexible building envelope. They requested the flex-
ibility for expansion of the building envelope both horizon-
tally and vertically to relocate residential units, relocate me-
chanical equipment that would be displaced from the lowest
floors, and to accommodate access elements. A second
idea proposed to raise the height of the ground floor above
the minimum design flood elevation requirements as an
incentive for the provision of a full floor at grade that could
facilitate activation through the permitted uses, although
limited to parking, building access, or storage.
All teams highlighted the importance of having a lively
22 DESIGN CHARRETTEFEBRUARY 2013
streetscape and ensuring activity at the street level. How-
ever, when designing for high flood elevations, having dry
floodproofed retail at grade level was described as likely
to be economically infeasible and difficult to implement.
Several solutions opted for lobbies at grade or public open
space and pop-up programs in lieu of abandoning the low-
est floors.
Several teams suggested the use of architectural ele-
ments, such as decks, terraces, canopies and porches to
help protect building entrances while adding movement
to the façade and to help engage the pedestrian visually.
On a similar approach, other teams explored landscaping
and site design solutions to not only mitigate the effects of
elevated buildings (aesthetics and accessibility), but also
to provide an added measure of safety by dissipating the
wave energy, for example by integrating berms on larger
sites. While more difficult to implement, teams recognized
the opportunity, where possible, to go beyond the scale
of individual buildings or lots and proposed solutions that
integrate multiple properties in order to solve the challenge
of flood protection and building access. A proposal for an
“elevated urban sidewalk” would provide a shared ramp
that could ease ADA accessibility compliance and create an
added public space.
Images: AIA New York
It was also suggested to extend some flood protection
requirements and zoning relief to buildings in the 500-year
floodplain as well.
Overall, the event highlighted the necessity to update
and align regulations for buildings in flood zones to accom-
modate flood resilience measures made more urgent by
Hurricane Sandy and ongoing rebuilding efforts.
DESIGNING FOR FLOOD RISK 23Integrated streetscape design elements in Soho
URBAN DESIGN PRINCIPLES
Neighborhoods and buildings should To support this, building design should
be designed to survive a flood event, foster:
but also be functional during normal Visual connectivity
non-flood conditions which will prevail Facade articulation
the vast majority of the time. Public Inviting access
streets and sidewalks should provide Neighborhood character
continuous and varied pedestrian ex- In this manner, efforts to improve the
periences that sustain a wide range of resilience of buildings can enable the
vibrant and walkable neighborhoods. city to adapt to climate change while
supporting, not compromising, quality
of life.
24 URBAN DESIGN PRINCIPLESWith this purpose, design solutions for resiliency should take into consideration
a set of physical and programmatic parameters:
First Floor Elevation Distance from Street Line
Raising a building’s first occupied In New York City and other dense
floor by a relatively small height is urban environments, buildings that are
often possible without adverse effects directly adjacent to the public side-
on the streetscape or deviating from walk are better situated to support an
common building forms. While this active streetscape. However, when
can pose access challenges for some buildings in flood zones are located
buildings on small or narrow lots, there close to the street line (property line),
are many design solutions that can be the effects of elevating a building –
used when constructing a building that blank walls, disconnection of retail
is elevated up to roughly three feet from the sidewalk – can be more
above adjacent grade. severe. Buildings set further back from
Above this height, issues of ac- the street may have opportunities for
cess and visual connectivity become reconciling grades, accommodating
more difficult to address – it becomes access elements, and mitigating the
difficult to accommodate larger ramps effect of blank walls or voids.
and stairs while maintaining unique Every neighborhood street may have
architectural features and visual a different set of considerations when
connectivity with ground-floor uses. evaluating appropriate proximity be-
Where the difference between design tween sidewalk and building. A com-
flood elevation and adjacent grade mercial corridor may depend on that
becomes higher than five feet, design close proximity for viability of the retail;
options are increasingly limited, there- whereas, a lower density residential
fore making building-scale resilience street may benefit from the wider
strategies that support a vibrant public setback to accommodate landscaping
realm a significant challenge. and porches.
HEIGHT ABOVE GRADE
HIGH
+7’
MEDIUM
NEAR FAR FARTHER
+0’ +10’ +25’
+3’
LOW
DISTANCE FROM PROPERTY LINE
0’
DESIGNING FOR FLOOD RISK 25Program and Uses Density and Diversity
Dry flood proofing is a technique that In New York City, many different
can help keep retail or other active neighborhoods and building typologies
uses closer to the sidewalk level, are subject to flood zone regulations.
preserving a familiar streetscape and Because of their structural charac-
a stronger physical and visual con- teristics, some building types can
nection to the public realm. Dry flood accommodate resiliency strategies
proofing may be costly or impractical, better than others (e.g. one-two family Efforts to improve the
especially at higher flood elevations, detached homes with front yards, resilience of buildings must
and is not allowed in purely residential tower-in-the-park, larger scale build-
also take into account the
buildings, where FEMA and building ings). Buildings with fewer constraints
code allow only parking, building ac- from site or adjacent buildings can effects on public space
cess or storage below the base flood more easily articulate lower portions and quality of life.
elevation. In these situations, creative of the structure, accommodate access
design solutions will be needed to elements within the site or building
maintain connections between the envelope, and better reconcile the first
building and the sidewalk, supporting habitable/active floor with the sidewalk
the vibrancy of our City streets and level while still ensuring a vibrant and
maintaining engagement and a sense active street frontage. This becomes
of safety for the pedestrian. more challenging for infill develop-
ments and attached and semi-de-
tached buildings in contextual neigh-
borhoods where street life and activity
at the street level is necessary for the
continued vibrancy of a neighborhood.
Lower density residential neighborhood in College Point, Queens
26 URBAN DESIGN PRINCIPLESCommercial street in Downtown Brooklyn
DESIGNING FOR FLOOD RISK 27Visual Connectivity / Active Street Frontage
Designers should maximize
visual connectivity between
the sidewalk and elevated
ground floor to support pe-
destrian-friendly streets and
neighborhoods.
Buildings should engage the side- the use of human scaled architectural
walk. Sidewalks with activity on elements, such as landscaping and
adjacent buildings support pedestri- articulated facades.
an-friendly neighborhoods. Where zoning and site planning
Building elements such as windows allow, setting the building back several
and doors are proportional to the feet from the street line may allevi-
human scale, are recognizable to the ate the effects of inactive frontages
passer-by and create a sense of secu- abutting the sidewalk. Generally, the
rity and comfort. further from the street line, the easi-
Buildings with elevated first floors er it is to mitigate higher differentials
can lose visual connection with the between grade level and the active
street. First floor elevations roughly first floor. Grading and landscaping or
up to three feet are common and do adding stoops and porches can create
not differ significantly from common visual interest for the pedestrian. This
conditions throughout the city. When visual interest enlivens the sidewalk.
first floors are two or three steps While setting back from the street
above grade, pedestrians still have full line can help mitigate issues deriving
visual access of the first active level of from this height differential, first floors
a building. A clear visual connection that are far from the sidewalk are
between the inside and the outside of particularly problematic for commercial
the building is still possible. streets where foot traffic and immedi-
When flood protection necessitates ate access and visibility is integral to
first floors to be more than three feet economic viability. This is especially
above grade, sidewalks may lose true when such conditions become
this animating active edge and visual extended along a city block.
connection.
One mitigation for these blank walls
along the sidewalk is to encourage
28 URBAN DESIGN PRINCIPLESFacade Articulation
When active uses are limit-
ed or distant from the side-
walk level design elements
defining the facade of a
building should be used to
create lively and interesting
streetscapes.
Architecture should contribute to access can give designers an opportu-
a lively and interesting streetscape, nity to create a human-scaled facade
especially within the immediate field of in a portion of a building’s ground floor;
view of the pedestrian. Good archi- however, lobbies have limited eco-
tecture comes in many forms, but nomic value compared with parking
variations in solids and voids, a play and storage.
of light and shadow across variegated When a building is at or close to
facades, and where possible, trans- the property line, façade articulation
parency into the activity of a building is particularly important because of
have all been proven to enliven a the proximity to the sidewalk. In this
streetscape. Long expanses of uni- situation the design of the base of
form materials typically contribute to a the building together with the use
deadening of the streetscape. of screenings and planting can help
Buildings that elevate the lowest break the monotony of a façade and is
floor to gain flood resilience are limited most important in defining the pedes-
to contain only garages, building trian experience. Further from the
access, storage, or crawl space below street line, the integration of other ele-
the flood elevation; all of which can ments like plantings, stairs or porches
lend themselves to featureless fa- and changes in grade level, would
cades. Whereas windows and doors help contribute to a more dynamic
have a natural relation to the human streetscape.
scale, garage doors typically relate
only to the scale of cars. Storage and
crawl space demand no proportion.
Lobbies and other types of building
DESIGNING FOR FLOOD RISK 29Inviting Access
Access elements should be
integrated in the overall
design of the building and
to appear more inviting to
the people walking by.
The transition between public and rise of 30 inches). Integration of these
private space is defined largely by elements within the building or site is
the design, proportions, and location still manageable and common at low
of the building’s access elements, DFEs. However, at medium to high
such as stairs, stoops, ramps and design elevations the physical space
lifts. Because of the nature of flood required to fit the access elements
resilient construction, access elements grows proportionally, making it diffi-
to elevated floors has become a key cult to reconcile grade level and first
architectural feature of the lowest por- floor when accessible entryways are
tion of a building, while also represent- required to be provided.
ing the physical and visual connection When the building frontage is at or
from the sidewalk. Access elements close to the street line, common prac-
that are poorly scaled to surroundings tice is to incorporate access within the
or awkwardly recessed can make a building envelope. This solution has to
building appear disconnected and a be skillfully integrated in the articula-
streetscape less welcoming. These tion of the façade to avoid blank walls.
elements should be integrated into the If setting back from the street, access
building and site design as seamlessly elements can be more easily incorpo-
as possible, offering a gradual and rated in the street frontage with turns,
legible connection to the observer. landings, recesses, landscaping, and
Building Code generally requires other site-design solutions.
new buildings to have entryways On local retail streets with smaller
accessible to persons with disabili- commercial spaces, floor area can be
ties, except small homes and some limited and the integration of accessi-
non-residential buildings (with limita- ble ramps may not be feasible. Small-
tions to the non-accessible square er businesses may prefer to avoid set-
footage), through ramps or, in some ting back from the streetline in order to
cases, elevators. keep a presence on the street. Where
Even at lower design elevations, floor plan allows it, access could be
ramps and access elements still solved inside while still ensuring a
require significant physical space visual connection to the sidewalk.
(ramps require a length of 30 feet for a
30 URBAN DESIGN PRINCIPLESNeighborhood Character
Designers should respect a
neighborhood’s character
by taking cues from existing
context in building massing,
fenestration, rooflines, and
other architectural elements.
Many streets and neighborhoods may well accommodate flood resil-
derive character and a sense of place ience standards while being consis-
from the relative uniformity of building tent with the built context. In medium
massing and materials. The City has density contextual neighborhoods,
regulations to protect the value, histor- given the constraints of the built con-
ical significance, and social cohesion text, typical proportions may change;
that arises from neighborhood charac- new infill developments may differ
ter through contextual zoning and in in height, introduce different access
some cases, landmark district desig- configurations and overall have larger
nation. Neighborhoods’ different char- impacts on the distinct character of a
acters are often defined by prevailing neighborhood.
heights or street wall alignments. Designers can respect a neighbor-
When designing for greater flood pro- hood’s character by taking cues from
tection, buildings may have to exceed existing context in building massing,
the height of neighboring buildings or fenestration, rooflines and other archi-
else set back to accommodate access tectural elements.
elements. On local retail corridors in the flood
While some variation in building form zone, businesses may be greatly
can contribute to the creation of a di- affected by resiliency standards. Some
verse and vibrant neighborhood fabric, may altogether disappear because
infill and reconstructed buildings that of the expense and constructabilty
deviate too much from characteristic hurdles of implementation of such re-
patterns can seem out of context and siliency measures. If these businesses
detract from the streetscape. disappear, this could have grave long-
In residential districts, particularly term consequences for the character
lower density with detached homes and ultimately the sustainability of
with BFEs below five feet above neighborhoods.
grade, existing housing typologies
DESIGNING FOR FLOOD RISK 31Elevated retail in Soho
RECOMMENDATIONS
Many coastal communities have ment like New York City to increased
become accustomed to the form build- flood risk requires a broader set of
ings must take in an area of coastal design strategies than in lower density
flood risk – buildings without base- environments.
ments or cellars, or sometimes raised Zoning is an important tool for
on piles. New York City by and large shaping buildings, and can promote
has not yet made this adjustment from good design alongside increased
its traditional building forms. flood protection. This report describes
Flood resilience can be achieved proposed amendments to New York
through a range of solutions and at City’s Zoning Resolution to enable
different scales of intervention by more versatile and desirable design
incorporating a combination of strate- solutions to accommodate flood-resil-
gies. Adapting a dense, urban environ- ient construction.
32 RECOMMENDATIONSChange the method of measuring building height to
allow added elevation for safety (freeboard).
In New York City, zoning measures building height is regulated by the sky
building heights from different “zero exposure plane, which is measured
points” in different districts. None from curb level, street walls may need
of these currently reflect the recent to be set back from the street line to
changes to Building Code to require accommodate the additional height.
freeboard above the designated To allow the construction of the full
base flood elevation. Because of this, building height and floor area while
elevating the first floor of a building to minimizing the need for streetwall set-
accommodate the most recent FEMA backs, height could be measured from
DFE flood elevations plus freeboard reduc- the elevation at which the lowest floor
es the height available to the building, is placed – the base flood elevation
and may even prevent use of the full plus freeboard.
floor area allowed. In districts where
Allow – and in some instances require – for
architectural elements and streetscape provisions to
mitigate visual disconnection between the elevated
first floor and the street.
A streetscape that engages the pe- can encourage, and in some cases
DFE destrian is important to the perceived require design features that promote a
level of comfort and security on the vibrant streetscape.
street. When flood-resistant construc- A planting buffer with shrubs or
tion requirements prevent active use trees, combined with other façade
at the lowest levels of a building, blank treatments such as vertical articula-
walls may result at street level. To alle- tion, can mitigate limited ground-floor
viate the potential for negative effects activity. Architectural elements like
on the pedestrian environment, zoning turns in an entry stair, porches or
Architectural elements can be used to mitigate the visual effects of elevated first floors on the streetscape
DESIGNING FOR FLOOD RISK 33decks for one and two family buildings commercial corridors, to promote
can mitigate the distance between a dynamic and pedestrian-friendly
grade and the first occupied floor of retail environment. There are multiple
a building, introduce an additional options for maximizing the contribution
horizontal visual feature that gives the of the façade to the retail environment.
façade more of a pedestrian scale, Dry floodproofing, where feasible, can
and bring “eyes on the street” with bring not only fenestration but also
a semi-private space closer to the entrances and retail floor space down
sidewalk. to the pedestrian level. Some degree
Where spaces below the DFE have of dry floodproofing can also minimize
sufficient clearance to become more the degree to which buildings must be Hybrid floodproofing strategy with commer-
than a crawlspace, the limited ac- elevated. In addition, hybrid strategies cial display space closer to the pedestrian
tivities allowed (parking, storage, or are possible involving elevation of level
building access) can still bring some interior space with wet floodproofing
activity to the street, mitigating what of entrances and a shallow area near
otherwise could be a blank wall. For windows, which can serve as display
one- and two-family homes in zones space. The feasibility of each of these
with medium to high DFEs (more than options will depend on many factors,
6 feet above grade), zoning could including the level of the DFE and the
allow additional elevation (to 9 feet cost of different floodproofing options.
above grade) to accommodate a full- Zoning can allow for a variety of
height space for parking, storage, or solutions, including raising the level at
access . which transparency is required to ac-
Zoning currently requires minimum commodate elevation of the building.
street wall transparency on some
Modify street wall requirements, floor area regula-
tions, and height regulations to allow larger building
access elements to be placed outside or inside the
building, as needed.
Where elevated buildings are locat- are located inside the building, they
ed close to the street line, two options count towards floor area, reducing
are available for resolving the differ- the amount of usable area within the
ence in elevation: stairs and ramps building. Adjustments to zoning could
can be located outside the building, relieve both of these problems.
or inside the building. Zoning issues Allowing greater flexibility to recess
can arise with either option. In many portions of the street wall would allow
zoning districts, a building’s streetwall exterior stairs and ramps to provide
is required to line up with adjacent access to an elevated first floor.
buildings or be located within a certain These recesses would also provide an
distance of the street line, to support opportunity to better integrate access
neighborhood character or promote an elements into the building’s articulation
active commercial environment. This and site design.
restricts the location of access ele- Long expanses of exterior ramping
ments on the exterior of the building. can create a disconnection between
Alternatively, when stairs and ramps the building and the adjacent public
34 RECOMMENDATIONSAccess elements integrated outside the building facade
realm and make building access cum- above it, the lengthy switchback ramps
bersome. The negative implications and stairs located outside the building
for the streetscape can be alleviated can dominate the streetscape and
by allowing the space necessary for divorce the building from the street. If
ramps and stairs to be exempted from located inside the building, these ac-
floor area when placed inside the cess elements can make ground floor
building. By allowing 100 square feet layout difficult or impossible, especially
to be deducted for each one foot of for narrow sites or for medium to small
elevation above sidewalk level, zoning commercial spaces. In these situa-
could enable buildings to bring these tions, allowing additional height suf-
access elements into the building ficient to create a full-height ground-
without reducing the amount of usable floor space could enable accessible
space allowed. entry at grade from the sidewalk, and
Where the DFE is substantially make possible other enhancements to
above grade but less than a full story the streetscape.
Access elements inside the building envelope help preserve streetwall alignment
DESIGNING FOR FLOOD RISK 35You can also read
