ELEVATION DESIGN GUIDELINES FOR HISTORIC PROPERTIES NEW JERSEY HISTORIC PRESERVATION OFFICE DEPARTMENT OF ENVIRONMENTAL PROTECTION December 2019 All components of the Elevation Design Guidelines or Historic Properties including all text, graphic design, photography and illustrations unless noted otherwise were prepared by Dominique M. Hawkins, FAIA, LEED AP with drafting assistance by Elsa De Leon. We would like to express our appreciation to Preservation Design Partnership, LLC the New Jersey Historic Preservation Office and P h i l a d e l p h i a , P e n n s y l v a n i a Department of Environmental Protection for w w w . p d p a r c h i t e c t s . c o m their support in the completion of this project. This material is based upon work assisted by a grant from the Department of the Interior, National Park Service. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of the Interior. Table of Contents 1. Flooding & Historic Buildings 1 2. Balancing Elevation & Preservation 7 3. Basic Improvements & Flood Resilience 11 4. Establish Neighborhood Parameters for Elevation 17 5. Illustrated Case Studies 35 Appendices A. Glossary 59 B. Flood Resources 67 FLOOD MITIGATION GUIDE FOR HISTORIC PROPERTIES NEW JERSEY HISTORIC PRESERVATION OFFICE DEPARTMENT OF ENVIRONMENTAL PROTECTION These Elevation Design Guidelines for Historic Properties were December 2019 prepared for the New Jersey Historic Preservation Office, Department of Environmental Protection as a companion to the Flood Mitigation Guide for Historic Properties. Reference to both documents is recommended. Superstorm Sandy proved devastating for many New Jersey communities. Sandy significantly damaged many historic buildings, some beyond repair. In the aftermath of the storm, municipalities were faced with the challenge of rebuilding in a manner that provided protection of its citizens and the character of their communities. (Photograph courtesy of NJ HPO/FEMA.) Flooding & Historic 1 Buildings BUILDING ELEVATION New Jersey’s history of settlement along waterways forms the basis for Elevated Building — A non-basement building the state’s development patterns. Some of the New Jersey’s earliest (i) built, in the case of a building in an Area communities are located along or near waterfronts, both coastal and of Special Flood Hazard, to have the top inland. Historic buildings and structures are increasingly vulnerable to of the elevated floor or, in the case of a the effects of environmental change including flooding from high tides building in a Coastal High-Hazard Area or and severe storms. As individual property owners are struggling with Coastal A Zone, to have the bottom of how to best protect their homes, local Historic Preservation Commissions the lowest horizontal structural member (HPCs) are challenged with balancing the level of desired protection with of the elevated floor, elevated above the maintenance of their community’s historic character. the base flood elevation plus freeboard Building elevation is a common option considered by residential property by means of piling, columns (posts and owners to improve flood resilience. Elevation is the process of raising piers), or shear walls parallel to the flow the habitable portion of a building above the anticipated flood level of the water, and to minimize future loss. Some of the benefits of properly completed (ii) adequately anchored so as not to impair building elevations are that they can significantly decrease future flood the structural integrity of the building damage and flood insurance premiums. However, elevation can be during a flood up to the magnitude of both costly and significantly impact the historic character of individual the base flood. properties and surrounding neighborhoods. In an Area of Special Flood Hazard “elevated The purpose of these Elevation Design Guidelines for Historic Properties building” also includes a building elevated by is to assist residential property owners and HPCs in the establishment means of fill or solid foundation perimeter of parameters for building elevation specific in their municipalities that walls with openings sufficient to facilitate is sensitive to the local historic character. These parameters consider the unimpeded movement of flood waters. localized flood risk; floodplain management requirements; parcel site In Areas of Coastal High Hazard and Coastal limitations; as well as building typology, style, and materials. A Zones “elevated buildings” also includes a building otherwise meeting the definition of “elevated building” even though the lower area is enclosed by means of breakaway walls. Elevation Design Guidelines for Historic Properties New Jersey Historic Preservation Office 1 December 2019 The pale blue dots on this Flood Insurance Rate Map of Lambertville, New Jersey indicate the Special Flood Hazard Areas (SFHAs). The SFHA (also known as the 1% annual chance flood, 100-year flood and base flood zone), has historically been subject to a 1% chance of flooding during any given year. In this case, the SFHA is defined as Zone AE, in which the base flood elevations are determined. The portions with the black dots represents areas of historically 0.2% annual chance flood (also known as the 500-year flood zone). Areas without dots have been determined to be outside of the historically 0.2% annual chance floodplain. It is important to highlight that these categories do not include future conditions due to climate change or other factors. (Map obtained through FEMA’s Map Service Center at https://mcs.fema.gov/ portal/home.) Elevation Design Guidelines for Historic Properties 2 New Jersey Historic Preservation Office December 2019 SPECIAL FLOOD HAZARD AREAS The Special Flood Hazard Area (SFHA) is area of the floodplain that has a 1% chance or 1-in-100 chance of flooding in any given year based upon historical data and known as the 100-year-floodplain. The SFHA includes two different flood zones on the FIRMs: A Zones and V Zones. The difference between the two zones is that V Zones are subject to storm-induced velocity wave action (for example, a beach house that could be inundated in a storm), while A Zones are not. Therefore, buildings and their foundations in V Zones must meet more stringent standards because of the forces they must withstand. (Refer to Building Foundations, page 31.) The flood vulnerability for this small cottage is much higher than its elevated neighbors. (Photograph courtesy of NJ HPO/FEMA.) Area of Special Flood Hazard —Land in the floodplain within a community subject to a one IDENTIFYING FLOOD RISK percent or greater chance of flooding in any given year. It is shown on the FIRM as Zone V, Flooding can occur from a variety of natural sources including storms, VE, V1-30, A, AO, A1 A30, AE, A99, or AH. precipitation, the ocean, bays, harbors, rivers, streams, and creeks. AH Zone — Areas subject to inundation by Flooding can also occur as a result of failures of man-made infrastructure 1-percent-annual-chance shallow flooding such as water and storm water systems, and dams. Although flood threat (usually areas of ponding) where average from infrastructure failure is often sudden and unpredictable, low-lying, depths are between one and three feet. Base flood prone areas located adjacent to or near waterways, also known as Flood Elevations (BFEs) derived from detailed floodplains, are mapped by the Federal Emergency Management Agency hydraulic analyses are shown in this zone. (FEMA). Information regarding a property’s flood vulnerability can be found on FEMA’s Flood Insurance Rate Maps (FIRMs) as well as Digital AO Zone — Areas subject to inundation by Flood Insurance Rate Maps (DFIRMs) available online through FEMA’s 1-percent-annual-chance shallow flooding Flood Map Service Center, which can be searched by street address. (usually sheet flow on sloping terrain) where (https://mcs.fema.gov/portal/home.) FIRMs serve as the basis for average depths are between one and three floodplain regulation and management, as well as a tool for determining feet. flood insurance premiums. However, both FIRMs and DFIRMs are based Coastal A Zone — The portion of the Special upon historical or current flood data and do not address future threats Flood Hazard Area (SFHA) starting from a such as subsidence or sea level rise. Velocity (V) Zone and extending up to the The FIRMs and DFIRMs identify the extent of the 1% floodplain of the landward Limit of the Moderate Wave Action ground, also known as the 100-year floodplain, or Special Flood Hazard (LiMWA) delineation. Where no V Zone is Area (SFHA), representing the properties at the greatest risk of flooding. mapped the Coastal A Zone is the portion Buildings outside of the SFHA with levels below grade, such as basements, between the open coast and the landward may be equally vulnerable to flooding. In addition, properties outside Limit of the Moderate Wave Action delineation. of designated floodplains often experience flooding during major storm Coastal A Zones may be subject to wave effects, events, such as hurricanes, tropical storms, and Nor’easters. velocity flows, erosion, scour, or a combination The best way to obtain an accurate flood risk assessment for a specific of these forces. Construction and development property is to acquire an Elevation Certificate from a licensed surveyor, in Coastal A Zones is to be regulated the same architect, or engineer. The Elevation Certificate will identify the height of as V Zones/Coastal High Hazard Areas. the lowest floor relative to the Base Flood Elevation (BFE) or SFHA. The Coastal High Hazard Area (V Zone) — An height of the lowest occupied floor, which may be the basement, can be area of special flood hazard extending from used to calculate flood insurance rates and determine the height to which offshore to the inland limit of a primary frontal the building must be protected to comply with the local municipality’s dune along an open coast and any other area floodplain management regulations.