Floodplain2009OD

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 1:12000.数字洪水保险费率地图（Digital Flood Insurance Rate Map, DFIRM）数据库收录了用于生成洪水风险数据的相关风险信息与配套支撑数据。其所采用的主要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，以及最低洪水风险区域。本DFIRM数据库源自洪水保险研究（Flood Insurance Studies, FISs）、此前发布的洪水保险费率地图（Flood Insurance Rate Maps, FIRMs）、为支撑前述FIS与FIRM成果所开展的洪水灾害分析，以及在可用情况下引入的新型测绘数据。上述FIS与FIRM成果均由美国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（UTM）投影与坐标系完成地球表面地理配准。DFIRM数据文件的平面控制规范，与1:12000比例尺测绘工作所需的平面控制规范保持一致。