Designing for Flood Risk - COASTAL CLIMATE RESILIENCE

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Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
COASTAL CLIMATE RESILIENCE

Designing
for Flood Risk
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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
Designing for Flood Risk - COASTAL CLIMATE RESILIENCE
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 INTRODUCTION
Hurricane 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        11
Battery 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 CONSTRUCTION
structed 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        13
with 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 CONSTRUCTION
Elevated 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       15
A-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 CONSTRUCTION
A 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                    17
Recent 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 CONSTRUCTION
beaches 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               19
DESIGN 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 CHARRETTE
MARCH 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       21
DESIGN 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 CHARRETTE
FEBRUARY 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      23
Integrated 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 PRINCIPLES
With 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           25
Program 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 PRINCIPLES
Commercial street in Downtown Brooklyn

          DESIGNING FOR FLOOD RISK       27
Visual 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 PRINCIPLES
Facade 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        29
Inviting 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 PRINCIPLES
Neighborhood 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       31
Elevated 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 RECOMMENDATIONS
Change 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          33
decks 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 RECOMMENDATIONS
Access 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         35
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