Logical_Consistency_Report:
When FEMA revises an FIS, adjacent studies are checked to ensure agreement between flood elevations at the boundaries. Likewise flood elevations at the confluence of streams studied independently are checked to ensure agreement at the confluence. The FIRM and the FIS are developed together and care is taken to ensure that the elevations and other features shown on the flood profiles in the FIS agree with the information shown on the FIRM. However, the elevations as shown on the FIRM may represent rounded whole-foot elevations. They must be shown so that a profile recreated from the elevations on the FIRM will match the FIS profiles within one half of one foot.
Completeness_Report:
Data contained in the NFHL reflects the content of the source materials. Features may have been eliminated or generalized on the source graphic, due to scale and legibility constraints. With new mapping, FEMA plans to maintain full detail in the spatial data it produces. However, older information is often transferred from existing maps where some generalization has taken place. Flood risk data are developed for communities participating in the NFIP for use in insurance rating and for floodplain management. Flood hazard areas are determined using statistical analyses of records of river flow, storm tides, and rainfall; information obtained through consultation with the communities; floodplain topographic surveys; and hydrological and hydraulic analysis. Generally, regulatory water surface elevations and/or regulatory floodways are published only for developed or developing areas of communities. For areas where little or no development is expected to occur, FEMA may generate flood risk data without published water surface elevations. Typically, only drainage areas that are greater than one square mile and with an average of one foot of flood depth or greater are studied.
Note: The NFHL reflects the most current information available when the distribution data set was created. Currently, not all areas of a State or Territory have effective FIRM Database data. As a result, users may need to refer to the effective FIRM for effective flood hazard information.