FEMA Flood Hazard Areas

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 UTM projection and coordinate system. The specifications for the horizontal control of DFIRM data files are consistent with those required for mapping at a scale of 1:12,000.

数字洪水保险费率地图（Digital Flood Insurance Rate Map, DFIRM）数据库呈现了用于构建洪水风险数据的相关风险信息及配套支撑数据集。该数据库采用的核心风险分级包括：年超越概率1%的洪水事件、年超越概率0.2%的洪水事件，以及低洪水风险区域。DFIRM数据库的数据来源包括洪水保险研究（Flood Insurance Studies, FIS）、此前发布的洪水保险费率地图（Flood Insurance Rate Maps, FIRMs）、为支撑FIS与FIRM编制所开展的洪水灾害分析，以及可获取的新型测绘数据。上述FIS与FIRM均由联邦紧急事务管理局（Federal Emergency Management Agency, FEMA）发布。该数据集文件采用通用横轴墨卡托（Universal Transverse Mercator, UTM）投影及坐标系实现地球表面地理配准。DFIRM数据文件的水平控制规格与1:12000比例尺制图的要求保持一致。