It Is Hurricane Season…
The Biggert-Waters Flood Insurance Reform Act of 2012 (Biggert-Waters Act) immediately eliminated subsidies for about 438,000 National Flood Insurance Program (NFIP) policies, but subsidies on an estimated 715,000 policies across the nation remain. Depending on factors such as policyholder behavior, the number of subsidized policies will continue to decline over time. For example, as properties are sold and the Federal Emergency Management Agency (FEMA) resolves data limitations and defines key terms, more subsidies will be eliminated. GAO analysis found that remaining subsidized policies would cover properties in every state and territory where NFIP operates, with the highest numbers in Florida, Louisiana, and California. In comparing remaining subsidized and nonsubsidized policies GAO found varying characteristics. For example, counties with the highest and lower home values had a larger percentage of subsidized versus nonsubsidized policies.
Data constraints limit FEMA’s ability to estimate the aggregate cost of subsidies and establish rates reflecting actual flood risks on previously subsidized policies. FEMA does not have sufficient historical program data on the percentage of full-risk rates that subsidized policyholders have paid to estimate the financial impact–in terms of the difference between subsidized and full-risk premium rates–to NFIP of subsidies. Also, because not all policyholders are required to provide documentation about their flood risk, FEMA generally lacks information needed to apply full-risk rates (as required by the Biggert-Waters Act) on previously subsidized policies. FEMA is encouraging these policyholders to voluntarily submit this documentation. Federal internal control standards state that agencies should identify and analyze risks associated with achieving program objectives and develop a plan for obtaining needed data. Without this documentation, the new rates may not accurately reflect a property’s full flood risk, and policyholders may be charged rates that are too high or too low relative to their risk of flooding.
Options from GAO’s previous and current work for reducing the financial impact of subsidies on NFIP include (1) adjusting the pace of subsidy elimination, (2) targeting assistance or subsidies based on financial need, or (3) increasing mitigation efforts, such as relocation or elevation that reduce a property’s flood risk. However, these options have advantages and disadvantages. Moreover, the options are not mutually exclusive, and combining them could help offset some disadvantages. FEMA should develop and implement a plan to obtain flood risk information needed to determine full-risk rates for properties with previously subsidized rates. FEMA agreed with the recommendation.
FEMA, which administers NFIP, estimated that in 2012 more than 1 million of its residential flood insurance policies–about 20 percent–were sold at subsidized rates; nearly all were located in high-risk flood areas. Because of their relatively high losses and lower premium rates, subsidized policies have been a financial burden on the program. Due to NFIP’s financial instability and operating and management challenges, GAO placed the program on its high-risk list in 2006. The Biggert-Waters Act eliminated subsidized rates on certain properties and mandated GAO to study the remaining subsidized properties. This report examines (1) the number, location, and characteristics of properties that continue to receive subsidized rates compared with full-risk rate properties; (2) the information needed to estimate the historic cost of subsidies and establish rates for previously subsidized policies that reflect the risk of flooding; and (3) options to reduce the financial impact of remaining subsidized policies. GAO analyzed NFIP data on types of policies, premiums, and claims and publicly available home value and household income data. GAO also interviewed representatives from FEMA, insurance industry associations, and floodplain managers.
The effects of the National Flood Insurance Program’s (NFIP) building requirements for elevating or flood-proofing agricultural structures in high-risk areas varied across selected communities, according to interviews GAO conducted with floodplain managers and farmers. Specifically:
Floodplain managers and 12 farmers in selected rural communities with whom GAO spoke in Louisiana, North Carolina, and North Dakota generally were not concerned about these requirements. Most of these farmers told GAO that they had land outside the high-risk areas where they could build or expand their structures, or they could elevate their structures relatively easily.
Floodplain managers in selected California communities told GAO that farmers in their communities had been adversely affected by the building requirements. They said that most farm land was in high-risk areas and elevation of structures would be difficult and costly—due to the relatively deep flood depths, structures would be required to be elevated up to 15 feet to comply with the building requirements. They also indicated that some structures were difficult to make watertight below the projected flood level (dry flood-proofing). According to a California floodplain manager and several farmers with whom GAO spoke, the farmers who were adversely affected by the building requirements have had to work around outdated Federal Emergency Management Agency (FEMA) guidance that does not fully address the challenges of vast and relatively deep floodplains or reflect industry changes. For example, the 1993 guidance from FEMA allowed an alternative flood-proofing technique (wet flood-proofing) that permits water to flow through certain agricultural structures in expansive high-risk areas. However, farmers in the California communities told GAO this was not a viable option because pests might enter openings and contaminate crops stored inside. FEMA typically updates guidance as needed but acknowledged the need for additional guidance that covers all of the different types of agricultural structures and reflects recent developments in the size and scale of farm operations, including supporting structures that were expensive to build and replace. Additional and more comprehensive guidance would allow FEMA to better respond to recent developments and structural needs in vast and deep floodplains. Some local floodplain managers, farmers, and lenders from the selected communities identified options to help farmers manage the challenges of building or expanding agricultural structures in high-risk areas, but many of the options would entail certain risks and may run counter to the objectives of NFIP. For example, one commonly cited option calls for exempting agricultural structures from building requirements, with farmers assuming all of the flood risk and opting out of federal disaster relief. Both FEMA and the experts noted such an exemption could set a precedent, leading others to ask for similar exemptions. Further, FEMA officials stated that the agency had no legal authority to allow farmers or any other group to opt out of disaster relief.
NFIP helps protect property in high-risk floodplains by, among other things, requiring communities that participate in the program to adopt floodplain management regulations, including building requirements for new or substantially improved structures such as elevating, dry flood-proofing, or wet flood-proofing structures. GAO was asked to evaluate the possible effects of NFIP, including its building requirements, on farmers in riverine areas that have a high risk of flooding. This report examines, among other things, the effects of building requirements on farmers in high-risk areas and options that could help address any challenges farmers face. To do this work, GAO analyzed laws, regulations, and FEMA policy and claims data; interviewed 12 state and local floodplain managers, 24 farmers, and 6 lenders in 8 selected communities in California, Louisiana, North Carolina, and North Dakota (selection based on geographic diversity, presence of high-risk flood areas, and type of farming that required on-site structures); and interviewed flood management and planning experts and FEMA officials.
Ms. Berrick: Thank you Mr. Chairman and ranking member Voinovich and members of the subcommittee. Thanks for inviting me to appear today to discuss the status of the integration and transformation of DHS. Shortly after the creation of DHS, as you’re aware, GAO designated its
implementation and transformation as high-risk in large part because DHS had to transform 22 agencies with their own management challenges into one department and the enormity of that effort. We also recognize that DHS faced significant challenges in building its management capacity
while at the same time implementing its critical homeland security and other missions. DHS has remained on our high-risk list since. My statement today addresses the challenges DHS faces in acquisition, information technology, financial management, and human capital
management; DHS’ progress in integrating its management functions within and across the department; and in the department’s progress in addressing issues that have contributed to GAO’s high-risk designation. DHS has made some important progress in strengthening its management
functions but needs to take additional action and demonstrate progress in addressing some long standing issues within its management areas. Key among these actions is executing plans that they’ve established in demonstrating results across all of these areas. For example, our work
has identified significant shortcomings in DHS’ ability to manage an expanding portfolio of complex acquisitions worth billions of dollars. DHS has revised its acquisition review process to include more detailed guidance and has clarified roles and authorities among other improvements but DHS has not effectively carried out all of their policies. A recent work found that over half of the major acquisition
programs we reviewed awarded contracts without department approval of documents essential to planning acquisitions and setting requirements. In addition, most of these programs we reviewed had cost schedule and performance shortfalls. With respect to financial management, as you’re
aware, the department has faced challenges in modernizing and integrating its financial management systems and has not yet implemented a consolidated department wide system although it has plans to do that. Since DHS’ creation the independent auditors have been unable to express
an opinion on its limited scope audit of DHS’ balance sheets. In an effort to integrate its management functions across DHS the department has put in place a number of common policies and procedures within individual management areas to help vertically integrate the department
with the components. However, DHS has placed less emphasis on integrating horizontally across the department to bring its management functions together for common processes and systems. DHS has also developed a plan to integrate its management functions, which we think is a step in the right direction and has a lot of positive aspects. However the plan lacks details on how the initiatives cited will get DHS to the end state of management integration and what that end state is.
The plan also doesn’t address how the department will measure its performance and its integration efforts or what the resource needs are and whether they will be available to follow through with these initiatives. In order to help DHS address the challenges that have contributed to the high risk designation we’ve identified and worked with DHS over the past year and earlier on the specific actions we believe they need to take to improve in these areas. Key among these actions is demonstrating measurable, sustainable progress and strengthening its management functions such as delivering acquisition programs with an established cost scheduled and performance thresholds.
We have worked with the department over the years to address these issues and will continue to do that moving forward. Senator Voinovich and Senator Akaka thank you very much for inviting GAO here today and thank you for your leadership on these very important issues and support of GAO’s work.
Flood maps inform communities about the local flood risk and help set minimum floodplain standards for communities to build safely and resiliently. They determine the cost of flood insurance, which helps property owners to financially protect themselves against flooding. The lower the degree of risk, the lower the flood insurance premium will be. Flood maps are also the basis for flood insurance rates through the National Flood Insurance Program. The process for developing and updating flood maps
The Administrator of FEMA should update existing guidance on mitigating the risk of flood damage to agricultural structures to include additional information that reflects recent farming developments and structural needs in vast and deep floodplains. FEMA agreed with the recommendation.
allows FEMA to work with state, tribal and local governments and communities and property owners at all steps of the process to incorporate the best available data into each community’s flood maps.
Recent updates to the national flood mapping program enable the agency to receive recommendations from the Technical Mapping Advisory Council (TMAC) to assist FEMA in continuing to manage the program using technically credible and scientific practices in identifying flood risk. The Council will also advise on the improved practices used to ensure property owners may be notified of the mapping model that will be used to map their flood risk and help determine their rates. The law also allows 30 days for public comment on the model and issue of any new maps. Property owners may also appeal and receive reimbursement for a successful appeal of certain maps. Communities will not be charged for map reissue due to habitat restoration projects, dam removal, culvert re-design or installation or the installation of fish passages.
FEMA must notify Members of Congress when constituents in their district/state will be affected by a flood mapping update. In accordance with these requirements, FEMA Congressional Affairs Division distributes Notices to Congress each month. To view these notices and find out more about mapping updates nationwide, you may visit: http://www.fema.gov/risk-mapping-assessment-planning.
The law allows 30 days for public comment on the model and issue of any new maps. Property owners may also appeal and receive reimbursement for a successful appeal of certain maps. And, communities will not be charged for map reissue due to habitat restoration projects, dam removal, culvert re-design or installation or the installation of fish passages.
To find out more about the national flood mapping program and view maps and map projects in progress, visithttp://www.fema.gov/national-flood-insurance-program-flood-hazard-mapping.
Incorporating the specifications outlined in its Atlantic Ocean and Gulf of Mexico Coastal Guidelines Update, FEMA works with other federal and state agencies, tribes, as well as regional entities and communities, to update coastal flood hazard information and produce new Flood Insurance Rate Maps (FIRMs) for coastal communities on the gulf coast.
Utilizing the updated 1-percent annual chance coastal flood elevations, the updated coastal flood hazard analysis increases the understanding of local flood risk, encourages mitigation efforts and improves the community’s resilience to flood losses (life, property, and business) on the gulf coast.
Due to its geographical location, natural weather patterns, rapid population growth and urban development in low-lying areas, the gulf coast is one of the most vulnerable flood areas in the U.S.
Affecting five states (Alabama, Florida, Louisiana, Mississippi and Texas), the gulf coast stretches across 17,141 miles of tidal shoreline and various ecosystems. An updated coastal flood study is necessary to obtain a more accurate understanding of the coastal flood hazards on the gulf coast. Incorporating new research methodologies and updated data collected from federal, state, academic and private sector organizations, the new FIRMs will provide individuals on the gulf coast with the tools required to prepare for as much flood hazard risk as possible.
To obtain information on the status of flood studies in specific gulf coast areas, please visit FEMA’s Regional Coastal Analysis and Mapping Gulf coast websites:
- FEMA Region IV Coastal Study (Alabama, Florida, Mississippi)
- FEMA Region VI Coastal Study (Louisiana, Texas)
For general information about the FEMA Regional offices responsible for managing the Gulf coastal flood studies, please visit the following websites:
Additional technical information for the Gulf coast can be found at:
- FEMA 550, Recommended Residential Construction for the Gulf Coast: Building on Strong and Safe Foundations, provides recommendations for rebuilding homes destroyed by hurricanes on the Gulf Coast.
- For More Information
- Find answers to many of your questions by visiting our Coastal Frequently Asked Questions page.
- The Coastal Flood Risk Resources page, organized by resource type, contains links to useful fact sheets, flyers, brochures and other helpful documents produced by FEMA, other federal agencies, state agencies, water management districts and other entities.
- Learn about what resources, grants and other information is available when Rebuilding After a Coastal Storm.
- Subscribe to the Coastal Flood Risks email updates.
Sustainable building design concepts are increasingly being incorporated into residential building design and construction through green building rating systems. While the environmental benefits associated with adopting green building practices can be significant, these practices must be implemented in a manner that does not compromise the building’s resistance to natural hazards. FEMA P-798, Natural Hazards and Sustainability for Residential Buildings (FEMA 2010b), examines current green building rating systems in a broader context. It identifies green building practices—the tools of today’s green building rating systems—that are different from historical residential building practices and that, unless implemented with an understanding of their interactions with the rest of the structure, have the potential to compromise a building’s resistance to natural hazards. FEMA P-798 discusses how to retain or improve natural hazard resistance while incorporating green building practices.
Through the years, FEMA, other Federal agencies, State and local agencies, and other private groups have documented and evaluated the effects of coastal flood and wind events and the
performance of buildings located in coastal areas during those events. These evaluations provide a historical perspective on the siting, design, and construction of buildings along the Atlantic,
Pacific, Gulf of Mexico, and Great Lakes coasts. These studies provide a baseline against which the effects of later coastal flood events can be measured. Within this context, certain hurricanes, coastal storms, and other coastal flood events stand out as being especially important, either
because of the nature and extent of the damage they caused or because of particular flaws they exposed in hazard identification, siting, design, construction, or maintenance practices. Many of
these events—particularly those occurring since 1979—have been documented by FEMA in Flood Damage Assessment Reports, Building Performance Assessment Team (BPAT) reports, and
Mitigation Assessment Team (MAT) reports. These reports summarize investigations that FEMA conducts shortly after major disasters. Drawing on the combined resources of a Federal,
State, local, and private sector partnership, a team of investigators
Coastal Flood and Wind Events This section summarizes major coastal flood and wind events in the United States from 1900 to 2010. Many of these events have led to changes in building codes, regulations, mapping, and mitigation practices. The map and timeline in Figure 2-1 provide a chronological list of the major coastal flood and wind events in combination with the major milestones resulting from the events. They show the evolution of coastal hazard Figure 2-1.
Map and timeline of significant coastal flood and wind events, and milestones for regulations, building codes,
The U.S. Caribbean Territories of the U.S. Virgin Islands and Puerto Rico are frequently hit by tropical storms and hurricanes. Damage in the Caribbean Territories is generally made worse by poor construction practices and less stringent building codes. In 1989, Hurricane Hugo destroyed many buildings in the U.S. Virgin Islands and Puerto Rico (York 1989). In 1995, the U.S. Virgin Islands and Puerto Rico were again struck by a hurricane. High winds from Hurricane Marilyn damaged roofs (Figure 2-6), allowing water to penetrate and damage building interiors (National Roofing Contractors Association [NRCA] 1996). This storm highlighted the need for more stringent building codes, and the U.S. Virgin Islands adopted the 1994 UBC. In 1998, the high winds and flooding from Hurricane Georges caused extensive structural damage in Puerto Rico. While not all of the damage could have been prevented, a significant amount could have been avoided if more buildings had been constructed to meet the requirements of the Puerto Rico building code and floodplain management regulations in effect at the time (FEMA 1999b). In 1999, as a result of FEMA BPAT recommendations, Puerto Rico adopted the 1997 UBC.
A Acceptable level of risk – The level of risk (above the minimum required by building code or
regulation) judged by the building owner and designer to be appropriate for a particular building.
Accretion – The result of sediment transport when more sediment moves into a shoreline segment than leaves it. Adjacent grade – Elevation of the natural or graded ground surface, or structural fill, abutting the walls of a building. See also Highest adjacent grade and Lowest adjacent grade.
Angle of internal friction (soil) – A measure of the soil’s ability to resist shear forces without failure.
Appurtenant structure – Under the National Flood Insurance Program, an “appurtenant structure” is “a structure which is on the same parcel of property as the principal structure to be insured and the use of which is incidental to the use of the principal structure.”B Barrier island – A long, narrow sand island parallel to the mainland. Base flood – Flood that has as 1-percent probability of being equaled or exceeded in any given year. Also known as the 100-year flood. Base Flood Elevation (BFE) – The water surface elevation resulting from a flood that has a 1 percent probability of equaling or exceeding that level in any given year. Elevation of the base flood in relation
to a specified datum, such as the National Geodetic Vertical Datum or the North American Vertical
Datum. The Base Flood Elevation is the basis of the insurance and floodplain management requirements of the National Flood Insurance Program. Basement – Under the National Flood Insurance Program, any area of a building having its floor subgrade on all sides. (Note: What is typically referred to as a “walkout basement,” which has a floor that is at or above grade on at least one side, is not considered a basement under the National Flood
Corrosion-resistant metal – Any nonferrous metal or any metal having an unbroken surfacing of
nonferrous metal, or steel with not less than 10 percent chromium or with not less than 0.20 percent
copper. Cross-shore sand transport – Wave- and/or tide-generated movement of shallow-water coastal sediments toward or away from the shoreline. See also Coastal sediment budget and Longshore sand transport. D Dead load – Weight of all materials of construction incorporated into the building, including but not limited to walls, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding, and other similarly incorporated architectural and structural items and fixed service equipment. See also Loads. Debris – Solid objects or masses carried by or floating on the surface of moving water, or carried by wind. Debris impact loads – Loads imposed on a structure by the impact of flood borne debris. These loads are often sudden and large. Though difficult to predict, debris impact loads must be considered when structures are designed and constructed. See also Loads. Design event – The minimum code-required event (for natural hazards, such as flood, wind, and earthquake) and associated loads that the structure must be designed to resist.
Design flood – The greater of either (1) the base flood or (2) the flood associated with the flood hazard
area depicted on a community’s flood hazard map, or otherwise legally designated.
Design Flood Elevation (DFE) – Elevation of the design flood, or the flood protection elevation
required by a community, including wave effects, relative to the National Geodetic Vertical Datum,
North American Vertical Datum, or other datum. The DFE is the locally adopted regulatory flood
elevation. If a community regulates to minimum National Flood Insurance Program (NFIP)
requirements, the DFE is equal to the Base Flood Elevation (BFE). If a community chooses to exceed
minimum NFIP requirements, the DFE exceeds the BFE. See ASCE-24, Flood Resistant Design and
Construction. Good engineering design practice requires elevation above the Base Flood Elevation.
Design flood protection depth – Vertical distance between the eroded ground elevation and the Design Flood Elevation. Design stillwater flood depth – Vertical distance between the eroded ground elevation and the design stillwater flood elevation. Design stillwater flood elevation – Stillwater elevation associated with the design flood, excluding wave effects, relative to the National Geodetic Vertical Datum, North American Vertical Datum, or other datum. See also Stillwater elevation.
Development – Under the National Flood Insurance Program, any manmade change to improved or
un-improved real estate, including but not limited to buildings or other structures, mining, dredging,
filling, grading, paving, excavation, or drilling operations or storage of equipment or materials. GLOSSARY COASTAL CONSTRUCTION MANUAL RESOURCES 5 Dry floodproofing – A flood retrofitting technique in which the portion of a structure below the flood protection level (walls and other exterior components) is sealed to be impermeable to the passage of floodwaters.
Dune – See Frontal dune and Primary frontal dune. Dune toe – Junction of the gentle slope seaward of the dune and the dune face, which is marked by a slope of 1 on 10 or steeper. E
Effective Flood Insurance Rate Map – See Flood Insurance Rate Map. Elevation – Raising a structure to prevent floodwaters from reaching damageable portions. Enclosure – The portion of an elevated building below the lowest elevated floor that is either partially or fully shut in by rigid walls.
Encroachment – The placement o prevent floodwaters from reaching damageable portions.
Enclosure – The portion of an elevated building below the lowest elevated floor that is either partially or fully shut in by rigid walls. Encroachment – The placement of an object in a floodplain that hinders the passage of water or otherwise affects the flood flows. Erodible soil – Soil subject to wearing away and movement due to the effects of wind, water, or other geological processes during a flood or storm or over a period of years. Erosion – Under the National Flood Insurance Program, the process of the gradual wearing away of land masses. Erosion analysis – Analysis of the short- and long-term erosion potential of soil or strata, including the effects of flooding or storm surge, moving water, wave action, and the interaction of water and structural components. Exterior-mounted mechanical equipment – Includes, but is not limited to, exhaust fans, vent hoods, air conditioning units, duct work, pool motors, and well pumps. Federal Emergency Management Agency (FEMA) – Independent agency created in 1979 to provide a single point of accountability for all Federal activities related to disaster mitigation and emergency preparedness, response, and recovery. FEMA administers the National Flood Insurance Program. Federal Insurance and Mitigation Administration (FIMA) – The component of the Federal Emergency Management Agency directly responsible for administering the flood insurance aspects of the National Flood Insurance Program as well as a range of programs designed to reduce future losses to homes, businesses, schools, public buildings, and critical facilities from floods, earthquakes, tornadoes,
and other natural disasters.
Fill – Material such as soil, gravel, or crushed stone placed in an area to increase ground elevations or
change soil properties. See also Structural fill.
Main Wind Force Resisting System (MWFRS) – Consists of the foundation; floor supports (e.g.,
joists, beams); columns; roof rafters or trusses; and bracing, walls, and diaphragms that assist in
transferring loads. The American Society of Civil Engineers (ASCE) 7-10 defines the MWFRS as “… an
assemblage of structural elements assigned to provide support and stability for the overall structure.”
Manufactured home – Under the National Flood Insurance Program, a structure, transportable in one or more sections, built on a permanent chassis and designed for use with or without a permanent foundation when attached to the required utilities. Does not include recreational vehicles.
Marsh – Wetland dominated by herbaceous or non-woody plants often developing in shallow ponds or depressions, river margins, tidal areas, and estuaries. Masonry – Built-up construction of building units made of clay, shale, concrete, glass, gypsum, stone, or other approved units bonded together with or without mortar or grout or other accepted methods of joining. Mean return period – The average recurrence interval of an event over an extended period of time. For example, the average time (in years) between landfall or nearby passage of a tropical storm or hurricane. See also Recurrence interval. Mean water elevation – The surface across which waves propagate. The mean water elevation is calculated as the stillwater elevation plus the wave setup. Mean sea level (MSL) – Average height of the sea for all stages of the tide, usually determined from hourly height observations over a 19-year period on an open coast or in adjacent waters having free access to the sea. See also National Geodetic Vertical Datum. Metal roof panel – Interlocking metal sheet having a minimum installed weather exposure of 3 square feet per sheet. Minimal Wave Action area (MiWA) – The portion of the coastal Special Flood Hazard Area where base flood wave heights are less than 1.5 feet.
Mitigation – Any action taken to reduce or permanently eliminate the long-term risk to life and property from natural hazards. Mitigation Assessment T
Start of construction (for other than new construction or substantial improvements under the
Coastal Barrier Resources Act) – Under the National Flood Insurance Program, date the building
permit was issued, provided the actual start of construction, repair, reconstruction, rehabilitation, addition placement, or other improvement was within 180 days of the permit date. The actual start means either the first placement of permanent construction of a structure on a site such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation; or the placement of a manufactured home on a foundation. Permanent construction does not include land preparation, such as clearing, grading, and filling; nor the installation of streets or walkways; excavation for a basement, footings, piers, or foundations or the erection of temporary forms; or the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling unit or not part of the main structure. For a substantial improvement, the actual start of construction means the first alteration of any wall, ceiling, floor, or other structural part of a building, whether or not that alteration affects the external dimensions of the building. State Coordinating Agency – Under the National Flood Insurance Program, the agency of the State government, or other office designated by the Governor of the State or by State statute to assist in the implementation of the National Flood Insurance Program in that State.
Stillwater elevation – The elevations of the water surface resulting solely from storm surge (i.e., the rise in the surface of the ocean due to the action of wind and the drop in atmospheric pressure association with hurricanes and other storms).
Structure – For floodplain management purposes under the National Flood Insurance Program (NFIP), a walled and roofed building, gas or liquid storage tank, or manufactured home that is principally above ground. For insurance coverage purposes under the NFIP, structure means a walled and roofed building, other than a gas or liquid storage tank, that is principally above ground and affixed to a permanent site, as well as a manufactured home on a permanent foundation. For the latter purpose, the term includes a building undergoing construction, alteration, or repair, but does not include building materials or supplies intended for use in such construction, alteration, or repair, unless such materials or supplies are within an enclosed building on the premises. Subsidence (land) – The ground level falling due to various geological processes. See also Uplift (land).Substantial damage – Under the National Flood Insurance Program, damage to a building (regardless of the cause) is considered substantial damage if the cost of restoring the building to its before-damage condition
would equal or exceed 50 percent of the market value of the structure before the damage occurred.
Substantial improvement – Under the National Flood Insurance Program, improvement of a building (such as reconstruction, rehabilitation, or addition) is considered a substantial improvement if its cost equals or exceeds 50 percent of the market value of the building before the start of construction of the improvement. This term includes structures that have incurred substantial damage, regardless of the actual repair work performed. The term does not, however, include either (1) any project for improvement of a structure to correct existing violations of State or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to ensure safe living conditions, or (2) any alteration of a “historic structure,” provided that the alteration will not preclude the structure’s continued designation as a “historic structure.”
Reinforced concrete foundations (including walls, columns, piers, piles, and pre-stressed elements) may be used in coastal construction, particularly in Zone A and in areas where wood piles cannot be readily driven or in cases where the superstructure will be constructed of concrete, masonry, or a combination of these materials. As an example, in the Florida Keys, concrete foundations are often socketed into a hole augured into the limestone or other bedrock. The concrete mix selection is an important factor in obtaining durable reinforced concrete in many environments.
Reinforced concrete typically has 1.5 or 2 inches of concrete over the steel reinforcement. This concrete cover, specified by the American Concrete Institute (ACI), must resist both salt-laden and freeze-thaw environments. Usually the steel reinforcement is protected from corrosion by the thickness of the concrete cover and the concrete’s natural alkalinity. However, in a coastal environment, chloride ions may penetrate the concrete cover, lowering the alkalinity and allowing the steel to corrode. Expansion of the cracks and spalls in the concrete cover allows more salt penetration and corrosion. Thus, concrete mixes for coastal construction must have superior durability properties to resist this action in addition to the required strength properties. The IBC and IRC require that the durability of a concrete mix subjected to salt intrusion be enhanced by a higher design strength and a lower water-cement ratio. Admixtures for the mix can be chosen to reduce the water-cement ratio for improved durability while maintaining workability. Both the coarse and fine aggregates should be chosen for even gradation and to avoid chemical reactions. If this durable concrete mix is correctly batched, placed, and cured, it is much less likely that the chloride ions will penetrate the concrete cover and cause the steel to corrode.
As in concrete construction, salt-laden moisture entering reinforced masonry through cracks, defects, or a thin masonry or concrete cover can cause the steel reinforcement to corrode, leading to spalling and loss of strength. Therefore, the choice of masonry unit, mortar, grout, and reinforcement materials is critical. For concrete masonry units, choosing Type I “moisture controlled” units and keeping them dry in transit and on the job site will minimize shrinkage cracking. For optimum crack control, Type S mortar should be chosen for below-grade applications, and type N mortar for aboveground applications. Horizontal ladder-type joint reinforcement, when used, is placed close to the wall surface in the mortar joint, and is therefore vulnerable to corrosion. This reinforcement, and other metal reinforcement accessories, should be hot-dip galvanized. Distributed horizontal and vertical reinforcement, which should have at least 2 inches of masonry shell and grout cover, may be of plain steel with all loose corrosion and salt removed. The IBC and IRC require, as a minimum, certificates for the materials used in masonry construction indicating compliance with construction documents. Reinforced masonry and concrete constructed as foundation walls must be supported by either a concrete footing or pile in order to transfer dead, live, and environmental loads to the soil. When a footing is used, the footing must be placed on undisturbed soil with a bearing capacity sufficient to support the building loads with minimal settlement. The footing should be reinforced with sufficient concrete cover as discussed above.