How accurate are the heights or depths?
• Where are the gaps in the data? What is missing? This data set contains bedrock unit boundaries, lithogeochemical boundaries, and rock group boundaries for the New England study area, which combines the CONN and NECB study units. The CONN NAWQA study unit includes most of Connecticut, western Massachusetts, eastern Vermont, western New Hampshire and small parts of Rhode Island, New York, and Quebec, Canada. The NECB NAWQA study area encompasses 23,000 square miles in western and central Maine, eastern Massachusetts, most of Rhode Island, and a small part of eastern Connecticut. Included in the NECB study area are the Kennebec, Androscogginn, Saco, Merrimack, Charles, and Blackstone River Basins as well as all of Cape Cod. • How consistent are the relationships among the observations, including topology? Every polygon has a single label point and all polygons are closed.
The DFIRM Database consists of countywide vector files and associated attributes produced in conjunction with the hardcopy FEMA FIRM. The published effective FIRM and DFIRM maps 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 Specifications for Flood Hazard Mapping Partners. Vertical accuracy was tested by manual comparison of source graphics with hardcopy plots and a symbolized display on an interactive computer graphic system. Independ
