The 100-year floodplain comprises areas that will be inundated by a flood event having a 1-percent chance of being equaled or exceeded in any given year. Derived from FEMA Flood Insurance Rate Maps. This information is intended for informational purposes only and should not be used for parcel-level determinations.

Provides the location of the pending FEMA 500-year floodplain (areas of 0.2-percent annual chance flood) plus areas with reduced risk due to levee. This information is intended for informational purposes only and should not be used for parcel-level determinations.

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, the 0.2-percent-annual- chance flood event, 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 the Federal Emergency Management Agency (FEMA). The file is georeferenced to earth's surface using the Universal Transverse Mercator Coordinate System (ZONE 18N). The specifications for the horizontal control of DFIRM data files are consistent with those required for mapping at a scale of 1:12,000.

A compilation of best available floodway boundaries. A floodway is the channel of a stream plus any adjacent floodplain area that must be kept free of encroachment so that the 1-percent annual chance flood can be carried without substantial increases in flood heights.

Authority: Executive Order No. 149: FEMA and Flood Plain Use. Jurisdiction: Floodplains in the Commonwealth of Massachusetts. Applicability: Construction by state agencies must avoid floodplains. State-administered grant and loan programs must avoid supporting construction in flood plains, to the extent possible. Regulatory Designates the Massachusetts Department of Conservation and Recreation (DCR, formerly the Department of Environmental Management) as the state coordinating agency to implement the National Flood Insurance Program. Requires all state agencies, to the extent possible, to avoid construction, provision of loans or grants, conveying, or permitting projects in floodplains. Provides for Massachusetts participation in the National Flood Insurance Program. Review Process: Contact the Federal Emergency Management Agency (FEMA) to determine if a proposed project is in a floodplain. Projects proposed in floodplains are reviewed in conjunction with Massachusetts Environmental Policy Act (15), Massachusetts Wetlands Protection Act (17), and Massachusetts Office of Coastal Zone Management (22) reviews. Technical assistance is also available from the DCR Flood Hazard Management Program. Forms: No additional forms for floodplain review. Fees No additional fees for floodplain review. Website: FEMA at http://store.msc.fema.gov/webapp/wcs/stores/servlet/FemaWelcomeView?storeId=10001&catalogId=10001&langId=-1 DCR Flood Hazard Management Program at http://www.mass.gov/dcr/stewardship/mitigate/.

Normally, any FIRM that has associated flood profiles has cross sections. The S_XS table contains information about cross section lines. These lines usually represent the locations of channel surveys performed for input into the hydraulic model used to calculate flood elevations. Sometimes cross sections are interpolated between surveyed cross sections using high accuracy elevation data. Depending on the zone designation (Zone AE, Zone A, etc.), these locations may be shown on Flood Profiles in the FIS report and can be used to cross reference the Flood Profiles to the planimetric depiction of the flood hazards. This information is used in the Floodway Data Tables in the FIS report, as well as on the FIRM panels.

Flood hazard areas identified on the Flood Insurance Rate Map are identified as a Special Flood Hazard Area (SFHA). SFHA are defined as the area that will be inundated by the flood event having a 1-percent chance of being equaled or exceeded in any given year. The 1-percent annual chance flood is also referred to as the base flood or 100-year flood. SFHAs are labeled as Zone A, Zone AO, Zone AH, Zones A1-A30, Zone AE, Zone A99, Zone AR, Zone AR/AE, Zone AR/AO, Zone AR/A1-A30, Zone AR/A, Zone V, Zone VE, and Zones V1-V30. Moderate flood hazard areas, labeled Zone B or Zone X (shaded) are also shown on the FIRM, and are the areas between the limits of the base flood and the 0.2-percent-annual-chance (or 500-year) flood. The areas of minimal flood hazard, which are the areas outside the SFHA and higher than the elevation of the 0.2-percent-annual-chance flood, are labeled Zone C or Zone X (unshaded).