FLOOD PLAIN
Status: Obtained in 1998
GENERAL DESCRIPTION
Q3 flood data produced by the Federal Emergency Management Agency (FEMA) for the Town of Brookline Area.
SOURCE/CONVERSION METHODOLOGY
This datalayer was created through joining two panels of the Q3 flood data from FEMA, clipping the joined data by Brookline Town Boundary GIS coverage, and projecting the clipped data into Massachusetts State Plane Coordinates NAD 83 feet, which matches Brookline GIS data coordinate system.
According to the FEMA’s Q3 flood data users guide, "the Q3 Flood Data are derived from the Flood Insurance Rate Maps (FIRMs) published by the Federal Emergency Management Agency (FEMA). The file is georeferenced to the earth's surface using the Universal Transverse Mercator (UTM) projection and a zonal coordinate system (units in meters). Specifications for the horizontal control of Q3 Flood Data files are consistent with those required for mapping at a scale of 1:24000.
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 1973 Flood Disaster Protection Act). 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 insurance coverage offered through the NFIP.
Q3 Flood Data files convey certain key features from the existing hard copy FIRM. Edge-matching errors, overlaps and deficiencies in coverage, and similar problems are not corrected during digitizing or post-processing. The Q3 Flood Data files are intended to provide users with automated flood risk data that may be used to locate SFHAs. More detailed information may be obtained from the paper FIRM." (Q3 Flood Data Users
Guide).COVERAGE NAME
FLOOD
FEATURE TYPE
POLYGONS
LINES
ATTRIBUTES
FLOOD Polygon Attribute Table:
| POS | ITEM NAME | W | W | T | D | DESCRIPTION |
| 1 | AREA | 8 | 8 | F | 5 | Polygon area |
| 9 | PERIMETER | 8 | 8 | F | 5 | Polygon perimeter |
| 17 | FLOOD# | 4 | 4 | B | 0 | Record number |
| 21 | FLOOD-ID | 4 | 4 | B | 0 | Polygon ID |
| 25 | TILE-NAME | 8 | 8 | C | ||
| 33 | COUNTY | 10 | 10 | C | ||
| 43 | FIPS | 5 | 5 | C | - | State and County FIPS codes |
| 48 | COMMUNITY | 4 | 4 | C | - | FEMA Community ID number |
| 52 | FIRM_PANEL | 11 | 11 | C | - | FIRM panel number |
| 63 | QUAD | 8 | 8 | C | - | USGS quadrangle identifier (Key to RQUAD files) |
| 71 | ZONE | 5 | 5 | C | - | Flood hazard zone |
| 76 | FLOODWAY | 5 | 5 | C | - | Floodway type |
| 81 | COBRA | 9 | 9 | C | - | COBRA identifier |
| 90 | SFHA | 3 | 3 | C | - | In/Out determination |
| 93 | SYMBOL | 4 | 5 | B | - | Polygon shade symbol |
| 97 | PANEL_TYP | 4 | 4 | C | - | Type of FIRM panel |
Sample record from the FLOOD polygon attribute table:
Record No. 6
| AREA | = |
59799.18365 |
| PERIMETER | = |
909.09371 |
| FLOOD# | = |
6 |
| FLOOD-ID | = |
8 |
| TILE-NAME | = |
126 |
| COUNTY | = |
NORFOLK |
| FIPS | = |
25021 |
| COMMUNITY | = |
0234 |
| FIRM_PANEL | = |
2502340008B |
| QUAD | = |
42071-C1 |
| ZONE | = |
A |
| FLOODWAY | = |
|
| COBRA | = |
COBRA_OUT |
| SFHA | = |
IN |
| SYMBOL | = |
3 |
| PANEL_TYP | = |
CBPP |
FIPS
This item contains the five-digit state and county FIPS code, as defined in the Federal Information Processing Standard Publication 6-4 (FIPS PUB 6-4), published by the National Institute of Standards and Technology. The state and county FIPS codes are further separated by the redefined items ST-FIPS and CO-FIPS.
COMMUNITY
This item contains the four-digit community identification number assigned by FEMA to each community that participates in the NFIP. This number may be found in the title block of each FIRM panel, or in the NFIP Community Status Book.
FIRM_PANEL
This item contains the eleven-digit FIRM panel number. The FIRM panel number is found in the title block of each FIRM panel. The FIRM panel number is further separated into its components by the redefined items STATE, (contains the state
FIPS code), PCOMM (for countywide panels this is the county FIPS code plus the letter "C", for community based panels this is the community identification number), and PANEL (the panel number and suffix).
QUAD
This item contains the eight-digit USGS quadrangle identification number. This item identifies the alphanumeric map sheet identifier used by the USGS. The list of values for each state is published by USGS in the State Indexes to Topographic and Other Map Coverage. This item is further separated into its components by three redefined items. They are: LAT (the latitude, rounded down to the nearest whole degree, of the 7.5-minute quadrangle map sheet), LONG (the longitude, rounded down to the nearest whole degree, of the 7.5-minute quadrangle map sheet), and QUAD_UNIT (the alphanumeric map sheet identifier used by USGS, A1 through H8).
ZONE
This item contains a representation of the flood hazard zone designator. The flood hazard zones are defined in Table: SFHA Zone Definition.
FLOODWAY
This item contains a representation of the floodway type. The floodway types are defined in Table: Floodway Area Definition. Floodway, Flowage Easement, and State Encroachment Areas are included in the Q3 Flood Data files if they are portrayed on the source graphic (the FIRM) used for data capture. If they are portrayed on a separate map panel (the Flood Boundary Floodway Map) they will not be digitized at this time.
COBRA
This item indicates whether the area is inside or outside of a designated Coastal Barrier Area or Otherwise Protected Area. Only the extents of the Coastal Barrier Resources Act area boundaries are portrayed in the Q3 Flood Data files. The boundaries between Coastal Barrier Resources Act areas and Otherwise Protected Areas and between areas with different designation dates are not included in the Q3 Flood Data files. Users should refer to the FIRM for such information. The COBRA types are defined in Table: COBRA Area Definition.
SFHA
This item indicates whether the area is in or out of the SFHA. It is derived from the area's Zone designation. The SFHA definitions that correspond with each of the Zone types are shown in Table: SFHA Zone Definition.
SYMBOL
This item represents a polygon shade symbol that is unique to the Zone, Floodway and COBRA area definitions. Users should note to use shadeset COLORNAMES.SHD if you use Arc/Info.
PANEL_TYP
This item contains a representation of the FIRM panel type.
SFHA Zone Definition Table
(Only the rows in Grey color apply to Brookline.)
| Zone Name | ZONE | SFHA | SYMBOL | Description |
| Zone V | V | In | 1 | An area
inundated by 100-year flooding with velocity hazard (wave action); no Base Flood Elevations(BFEs) have been determined. |
| Zone VE | VE | In | 2 | An area inundated by 100-year flooding with velocity hazard (wave action); BFEs have been determined. |
| Zone A | A | In | 3 | An area inundated by 100-year flooding, for which no BFEs have been determined. |
| Zone AE | AE | In | 4 | An area inundated by 100-year flooding, for which BFEs have been determined. |
| Zone AO | AO | In | 5 | An area
inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average depths have been determined; |
| Zone AO (Alluvial Fan) | AOVEL | In | 6 | An alluvial fan inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average flood depths and velocities have been determined; flood depths range from 1 to 3 feet. |
| Zone AH | AH | In | 7 | An area inundated by 100-year flooding (usually an area of ponding), for which BFEs have been determined; flood depths range from 1 to 3 feet. |
| Zone A99 | A99 | In | 8 | An area inundated by 100-year flooding, for which no BFEs have been determined. This is an area to be protected from the 100-year flood by a Federal flood protection system under construction. |
| Zone D | D | Out | 9 | An area of undetermined but possible flood hazards. |
| Zone AR | AR | In | 10 | An area inundated by flooding, for which BFEs or average depths have been determined. This is an area that was previously, and will again, be protected from the 100-year flood by a Federal flood protection system whose restoration is Federally funded and underway. |
| Zone X (500- year) | X500 | Out | 11 | An area inundated by 500-year flooding; an area inundated by 100- year flooding with average depths of less than 1 foot or with drainage areas less than 1 square mile; or an area protected by levees from 100- year flooding. |
| Zone X | X | Out | 12 | An area that is determined to be outside the 100- and 500-year floodplains. |
| 100-year Flood Discharge Contained in Channel | 100IC | In | 13 | An area where
the 100-year flooding is contained within the channel banks and the channel is too narrow to show to scale. An arbitrary channel width of 3 meters is shown. BFEs are not shown in this area, although they may be reflected on the corresponding profile. |
| 500-year Flood Discharge Contained in Channel | 500IC | Out | 14 | to scale. An arbitrary channel width of 3 meters is shown. |
| Floodway Contained in Channel | FWIC | In | 15 | An area where the floodway is contained within the channel banks and the channel is too narrow to show to scale. An arbitrary channel width of 3 meters is shown. BFEs are not shown in this area, although they may be reflected on the corresponding profile. |
| Flood Prone Area | FPQ | In | 16 | An area designated as a "Flood Prone Area" on a map prepared by USGS and the Federal Insurance Administration. This area has been delineated based on available information on past floods. This is an area inundated by 100-year flooding for which no BFEs have been determined. |
| Area in SFHA | IN | In | 17 | An area designated as within a "Special Flood Hazard Area" (or SFHA) on a FIRM. This is an area inundated by 100-year flooding for which BFEs or velocity may have been determined. No distinctions are made between the different flood hazard zones that may be included within the SFHA. These may include Zones A, AE, AO, AH, A99, AR, V, or VE. |
| Area Outside SFHA | OUT | Out | 18 | This is an area inundated by 500-year flooding; an area inundated by 100-year flooding with average depths of less than 1 foot or with drainage areas less than 1 square mile; an area protected by levees from 100-year flooding; or an area that is determined to be outside the 100- and 500-year floodplains. No distinctions are made between these different conditions. These may include both shaded and unshaded areas of Zone X. |
| Area Not Included | ANI | Out | 0 | An area that is located within a community or county that is not mapped on any published FIRM. |
| Area of Undesignated Flood Hazard | UNDES | Out | 0 | A body of open water, such as a pond, lake ocean, etc., located within a community's jurisdictional limits, that has no defined flood hazard. |
| Floodway Type | FLOODWAY | Description |
| Floodway | FW | An area that includes the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water-surface elevation by more than a designated height. (Note: this area is normally in Zone AE.) |
| Flowage
Easement Area |
EASE | An area within a community, usually bordering a stream, that has more restrictive floodplain development criteria imposed upon it by the governing body (town, city, etc.) than the criteria imposed as a prerequisite to participation in the NFIP. (Note: Unlike the floodway, this area may overlap any other flood zone.) |
| State Encroachment Area | STATE | An area within a community, usually bordering a stream, that has more restrictive floodplain development criteria imposed upon it by the state, than the criteria imposed as a prerequisite to participation in the NFIP. (Note: Unlike the floodway, this area may overlap any other flood zone.) |
COBRA Area Definition Table:
| COBRA Type | COBRA | Description |
| Inside COBRA or OPA area | COBRA_IN | An area designated as an Undeveloped Coastal Barrier Area or Otherwise Protected Area in which flood insurance is unavailable for structures newly built or substantially improved. |
| Outside COBRA or OPA area | COBRA_OUT | An area outside a designated Undeveloped Coastal Barrier Area or Otherwise Protected Area in which flood insurance is unavailable for structures newly built or substantially improved. |
COORDINATE SYSTEM
Massachusetts State Plane North America Datum (NAD) 83 Feet