COASTAL BARRIER RESOURCES SYSTEM (CBRS) POLYGONS OF THE DIGITAL FLOOD INSURANCE RATE MAP (DFIRM) IN THE STATE OF FLORIDA - OCTOBER 2017

Abstract:

This dataset contains information about the Coastal Barrier Resources System Boundaries (CBRS) within a study area. The Coastal Barrier Resources Act (CBRA) of 1982 established the John H. Chafee Coastal Barrier Resources System (CBRS), comprised of undeveloped coastal barriers along the Atlantic, Gulf, and Great Lakes coasts. The law encourages the conservation of hurricane prone, biologically rich coastal barriers by restricting Federal expenditures that encourage development, such as Federal flood insurance through the National Flood Insurance Program. CBRA is a free-market approach to conservation. These areas can be developed, but Federal taxpayers do not underwrite the investments. CBRA saves taxpayer dollars and encourages conservation at the same time. CBRA has saved over $1 billion and will save millions more in the future. Approximately 3.1 million acres of land and associated aquatic habitat are part of the CBRS. The Fish and Wildlife Service maintains the repository for CBRA maps enacted by Congress that depict the CBRS. The Service also advises Federal agencies, landowners, and Congress regarding whether properties are in or out of the CBRS, and what kind of Federal expenditures are allowed in the CBRS. The Digital Flood Insurance Rate Map (DFIRM) Database depicts flood risk information and supporting data used to develop the risk data. The primary risk classifications used are the 1-percent-annual-chance flood event (100 year), the 0.2-percent-annual-chance flood event (500 year), and areas of minimal flood risk. The DFIRM Database is derived from Flood Insurance Studies (FISs), previously published Flood Insurance Rate Maps (FIRMs), flood hazard analyses performed in support of the FISs and FIRMs, and new mapping data, where available. The FISs and FIRMs are published by FEMA. This dataset is an update to the DFIRM_CBRS_MAY16 layer.

Purpose:

The FIRM is the basis for floodplain management, mitigation, and insurance 
activities for the National Flood Insurance Program (NFIP). Insurance applications 
include enforcement of the mandatory purchase requirement of the Flood Disaster 
Protection Act, which "... requires the purchase of flood insurance by property 
owners who are being assisted by Federal programs or by Federally supervised, 
regulated or insured agencies or institutions in the acquisition or improvement of 
land facilities located or to be located in identified areas having special flood 
hazards, " Section 2 (b) (4) of the Flood Disaster Protection Act of 1973. In addition 
to the identification of Special Flood Hazard Areas (SFHAs), the risk zones shown 
on the FIRMs are the basis for the establishment of premium rates for flood 
coverage offered through the NFIP. The FIRM Database presents the flood risk 
information depicted on the FIRM in a digital format suitable for use in electronic 
mapping applications. The FIRM Database serves to archive the information 
collected during the Flood Risk Project.

Supplemental_Information:

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**The Following Information Contains The GeoPlan Center Process Steps: Indented Format** 
The GeoPlan Center downloaded the Statewide National Flood Hazard Layer 
from the following FEMA website on October 13th, 2017.

FEMA Flood Map Service Center
https://msc.fema.gov/portal
Search All Products
https://msc.fema.gov/portal/advanceSearch

Choose one of the three search options below and optionally enter a posting date range.
https://msc.fema.gov/portal/advanceSearch
State -FLORIDA
County - ALACHUA
Community - ALACHUA
 Search
 Effective Products
  NFHL Data-State(1)

Product ID Latest Study Effective Date Latest LOMR Effective Date Size Download
NFHL_12_20171006 10/05/2017 10/06/2017 1975MB

NFHL_12_20171006.zip
NFHL_12_20171006.gdb
  Feature Layer: S_CBRS

The S_CBRS was originally in the following projection:

GCS_North_American_1983
WKID: 4269 Authority: EPSG

Angular Unit: Degree (0.0174532925199433)
Prime Meridian: Greenwich (0.0)
Datum: D_North_American_1983
  Spheroid: GRS_1980
    Semimajor Axis: 6378137.0
    Semiminor Axis: 6356752.314140356
    Inverse Flattening: 298.257222101

The dataset was projected to the FGDL Albers HARN projection using the following Transformation:
NAD_1983_To_HARN_Florida

The dataset was renamed to dfirm_cbrs_oct17.

Next the following fields were added and populated:
PRODUCT_ID = "NFHL_12_20171006"
DESCRIPT = CBRS_TYP
FGDLAQDATE = "10/13/2017"
AUTOID = OBJECTID

No methodology was performed by GeoPlan to correct for geometry issues.
For more information on FEMA's Final Data Structure concerning sliver polygons 
please see below.
The FEMA report frm_gsal.pdf states the following regarding sliver polygons.
L.3.5.2 Topology
Vector data files must meet the following data structure requirements:
* Area spatial features for a given theme must cover the entire study area 
without overlaps, underlaps or sliver polygons between adjacent polygons.

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** The following FEMA DFIRM information is from the frm_gsalb.pdf ** 
Table: S_CBRS This table only applies to coastal areas that have specially 
protected areas designated by Congress on John H. Chafee Coastal Barrier 
Resources System (CBRS) maps. Authoritative CBRS boundary locations are 
shown on these maps administered by the U.S. Fish and Wildlife Service. Normally 
these areas are already shown on existing Federal Emergency Management 
Agency (FEMA) maps for the area. CBRS areas have restrictions on Federal funding
(including flood insurance coverage) after specified dates for new or substantially 
improved structures. See Section 2.2 and Appendix K of these Guidelines for more 
detailed information about CBRS areas. The S_CBRS table contains information 
about the CBRS areas within the study area, if applicable. A spatial file with 
locational information also corresponds with this data table. The spatial elements 
representing CBRS features are closed polygons. Each contiguous CBRS area of 
the same CBRS_TYP and same CBRS_DATE must be a single polygon. This is a 
Standard DFIRM Database table. What are Coastal Barriers? Coastal barriers are 
unique land forms that provide protection for diverse aquatic habitats and serve as 
the mainland's first line of defense against the impacts of severe coastal storms and 
erosion. Located at the interface of land and sea, the dominant physical factors 
responsible for shaping coastal land forms are tidal range, wave energy, and 
sediment supply from rivers and older, pre-existing coastal sand bodies. Relative 
changes in local sea level also profoundly affect coastal barrier diversity. Coastal 
barriers: * Consist primarily of unconsolidated sediments (sand, gravel, etc.); * are 
subject to wind, wave, and tidal energies; * are subject to the impacts of coastal 
storms and sea-level rise; * buffer the mainland from the impact of storms; * include 
associated landward aquatic habitats that are protected from direct wave attack by 
the fastland (non-wetland) portion of the coastal barrier; and * protect and maintain 
productive estuarine systems which support the Nation's fishing and shellfishing 
industries; Types of Coastal Barriers Coastal barriers may be described by their 
relationships to the mainland as bay barriers, tombolos, barrier spits, and barrier 
islands. Additional areas which function as coastal barriers include dune and beach 
barriers, and fringing mangroves. The term "mainland" includes the continental land 
mass as well as large  islands such as Long Island, New York and the Hawaiian 
Islands. Definitions of the various kinds of coastal barriers follow. * Bay barriers - 
coastal barriers that connect two headlands, and enclose a pond, marsh, or other 
aquatic habitat. The terms bay mount bar and bay bar are synonymous. * Tombolos 
- sand or gravel beaches which connect one or more offshore islands to each other 
or to the mainland. The terms connecting bar, tie bar, and tying bar are 
synonymous. * Barrier spits - coastal barriers that extend into open water and are 
attached to the mainland at only one end. They can develop into a bay barrier if 
they grow completely across a bay or other aquatic habitat. On the other hand, bay 
barriers can become spits if an inlet is created. * Barrier islands - coastal barriers 
completely detached from the mainland. Barrier spits may become barrier islands if 
their connection to the mainland is severed by creation of a permanent inlet. The 
barrier island represents a broad barrier beach, commonly sufficiently above high 
tide to have dunes, vegetated zones, and wetland areas. * Dune or beach barriers -
broad sandy barrier beaches, with hills or ridges of sand formed by winds, which 
protect landward aquatic habitats. * Fringing mangroves - bands of mangrove along 
subtropical or tropical mainland shores in areas of low wave energy. Many of these 
areas are located behind coral reefs, which together with the mangroves 
themselves, provide significant protection for the mainland from storm impact. 
Location of Coastal Barriers Coastal barriers occur on all the coastlines of the United
States. One of the longest and best defined chains of coastal barriers in the world 
occurs along the United States shoreline bordering the Atlantic Ocean and the Gulf 
of Mexico. This chain contains over 400 barriers and totals about 2,700 miles of 
shoreline. The coastal barriers from Maine to Texas show a high degree of regional 
diversity, controlled by differences in climate and in the physical processes shaping 
barrier shorelines. Long, continuous barriers with small ebb-tidal deltas are produced 
by longshore currents along wave-dominated coasts. These barriers are typified by 
the coastal barrier islands along the south Texas coast which are long, generally 
narrow, and cut by widely separated tidal inlets with large sand accumulations in the
back-barrier bays, and small or nonexistent seaward shoals. Similar barrier islands 
are also found in parts of Louisiana, the Florida panhandle, southeast Florida, North 
Carolina's Outer Banks, the south shore of Long Island, and the Cape Cod segment
of the Massachusetts coast. Tide-dominated coastlines support large ebb-tidal 
deltas. The Georgia coastal barrier islands typify a tide-dominated coastline: they are
relatively short and stubby and are separated by stable tidal inlets with an average 
spacing of 9 miles. Tide-dominated barriers also occur in northeast Florida, most of 
South Carolina's coast, along the Delmarva Peninsula, Massachusetts, and in some 
areas of Louisiana and Texas. Secondary Barriers If a suitable sediment source 
and sufficient wind, waves, and tidal energy exist, a secondary barrier may occasionally 
form behind the seaward coastal barrier. Secondary barriers are located in large, 
well-defined bays or in lagoons on the mainland side of coastal barrier systems. 
These barriers are maintained primarily by internally generated wind waves rather 
than open ocean waves. Consequently, secondary barriers are generally smaller 
and more ephemeral than barriers along the open coast. Nonetheless, these barriers 
are formed of unconsolidated sediments just like most oceanic barriers and, more 
importantly, they also protect vital fish and wildlife habitat and provide substantial 
protection for the mainland during major storms. Value of Coastal Barriers Coastal 
barriers provide invaluable services that are the foundations of a strong economy 
and healthy environment. They offer habitats that support a variety of fish and wildlife, 
protect mainland communities from severe storms, serve as popular vacation 
destinations, and support local economies. Coastal Barriers and Natural Resources 
Coastal barriers protect the aquatic habitats between the barrier and the mainland 
which contain resources of extraordinary scenic, scientific, recreational, natural, 
historic, and economic value. Together with their adjacent wetland, marsh, estuarine, 
inlet, and nearshore water habitats, coastal barriers support a tremendous variety 
of organisms. Millions of fish, shellfish, birds, mammals, and other wildlife depend on 
barriers and their associated wetlands for vital feeding, spawning, nesting, nursery, 
and resting habitat. These habitats are also critically important for many species 
harvested in the Nation's commercial fish and shellfish industries. The barrier and its 
associated habitats are one ecological system, and the health and productivity of the 
entire system depend on the rational use of all the component parts. Coastal Barriers 
and Severe Storms Under normal weather conditions, only aquatic habitats 
immediately adjacent to coastal barriers are exposed to direct wave attack. However, 
major coastal storms routinely affect the entire landward aquatic habitat. This habitat 
survives major storms because coastal barriers receive the brunt of the ocean's 
energies. Storm waves break on the barrier beach, leaving a diminished wave to travel 
into the wetland. At the same time, the wetland stores storm flood waters, easing the 
flood pressure on the mainland. Without extensive sand beaches protecting many 
bluffs and terraces, damages from violent storms would be much greater. Sand acts as 
a brake or drag on waves. Where there are barrier beaches fronting embayments, the 
sand absorbs the energy much as it does at the base of cliffs. The principal danger to 
beaches and barriers is not intense storms but a steady reduction in the sand supply 
caused by dams on tributary streams and the diversion or interruption of littoral transport 
along the seaward edge of beaches and barriers by bulkheads, groins, and jetties. In 
some situations, mining of beach sand has contributed to the problem. Spits and low-lying 
barrier beaches survive severe storms with relatively slight effects as long as there is a 
supply of sand available to restore the beach. A severe storm is a short-term phenomenon, 
repeating the annual cycle of changing width and slope of the beach within a few hours. 
Sometimes a spit is eroded back or shortened and the dunes reduced or moved, but the 
sand begins to build up again towards its equilibrium condition almost as soon as the storm 
ends. The entrance to a bay and/or river mouth may be relocated or shoaled, but this 
sometimes also happens without storms. Shoaling of harbor entrances may be dangerous 
to navigation and require dredging to restore an entrance channel. Development of Coastal 
Barriers Besides bearing the brunt of impacts from storms and erosion, most coastal barriers 
are made of unconsolidated sediments (sand, gravel, etc.). This geological composition 
alone makes them highly unstable areas on which to build. Despite their instability, many 
coastal barriers have been developed. In the past, this development was encouraged by 
the availability of Federal flood insurance and other types of Federal financial assistance. 
Through its unique free-market approach to conservation, the Coastal Barrier Resources 
Act has been instrumental in ensuring that the Federal government does not encourage the 
development of these coastal barrier habitats.
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Currentness_Reference:

publication date

Attribute_Accuracy_Report:

The NFHL incorporates all FIRM Databases published by FEMA and any LOMRs 
that have been issued against those databases since their publication date. The 
NFHL consists of vector files and associated attributes produced in conjunction 
with the hardcopy FEMA FIRM. The published effective FIRM and FIRM Database 
are issued as the official designation of the SFHAs. As such they are adopted by 
local communities and form the basis for administration of the NFIP. For these 
purposes they are authoritative. Provisions exist in the regulations for public review, 
appeals and corrections of the flood risk information shown to better match real 
world conditions. As with any engineering analysis of this type, variation from the 
estimated flood heights and floodplain boundaries is possible. Details of FEMA's 
requirements for the FISs and flood mapping process that produces these data are 
available in the Guidelines and Standards for Flood Risk Analysis and Mapping. 
Attribute accuracy was tested by manual comparison of source graphics with 
hardcopy plots and a symbolized display on an interactive computer graphic system.
Independent quality control testing of the individual FIRM Database components of 
the NFHL was also performed. To obtain more detailed information in areas where 
Base Flood Elevations (BFEs) and/or floodways have been determined, users are 
encouraged to consult the Flood Profiles and Floodway Data and/or Summary of 
Stillwater Elevations tables contained within the FIS reports that accompany the 
individual FIRM Database components of the NFHL. Users should be aware that 
BFEs shown in the S_BFE table may represent rounded whole-foot elevations. 
These BFEs are intended for flood insurance rating purposes only and should not 
be used as the sole source of flood elevation information. Accordingly, flood 
elevation data presented in the FIS report must be used in conjunction with the 
FIRM for purposes of construction and/or floodplain management. The 1-percent-
annual-chance water-surface elevations shown in the S_XS table match the 
regulatory elevations shown in the FIS report.

Entity_and_Attribute_Overview:

The DFIRM Database is made up of several data themes containing both spatial 
and attribute information. These data together represent the current flood risk for the
subject area as identified by FEMA. The attribute tables include SFHA locations, 
flood zone designations, BFEs, political entities, cross-section locations, FIRM panel
information, and other data related to the NFIP.

Table containing attribute information associated with the data set.
FEMA FIRM Database Technical Reference 
(available in the FEMA Library at http://www.fema.gov/media-library/assets/documents/34519).

Entity_and_Attribute_Detail_Citation:

Appendix L of FEMA's Guidelines and Specifications for FEMA Flood Hazard 
Mapping Partners contains a detailed description of each attribute code and a 
reference to other relevant information. The following tables are included in this data
set: l_comm_info l_stn_start study_info s_bfe s_base_index s_firm_pan 
s_fld_haz_ar s_fld_haz_ln s_gen_struct s_label_ld s_perm_bmk s_pol_ar s_pol_ln 
s_quad_index s_wtr_ln s_xs s_label_pt