FEMA Flood Insurance Rate Map Panel Index

The National Flood Hazard Layer (NFHL) data incorporates all Digital Flood Insurance Rate Map(DFIRM) databases published by Federal Emergency Management Agency (FEMA), and any Letters Of Map Revision (LOMRs) that have been issued against those databases since their publication date. The DFIRM Database is the digital, geospatial version of the flood hazard information shown on the published paper Flood Insurance Rate Maps(FIRMs). 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 NFHL data are 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 specifications for the horizontal control of DFIRM data are consistent with those required for mapping at a scale of 1:12,000. The NFHL data contain layers in the Standard DFIRM datasets except for S_Label_Pt and S_Label_Ld. The NFHL is available as State or US Territory data sets. Each State or Territory data set consists of all DFIRMs and corresponding LOMRs available on the publication date of the data set.

国家洪水灾害图层（National Flood Hazard Layer，NFHL）数据整合了美国联邦紧急事务管理署（Federal Emergency Management Agency，FEMA）发布的全部数字洪水保险费率图（Digital Flood Insurance Rate Map，DFIRM）数据库，以及自上述数据库发布之日起针对其出具的所有地图修订函（Letters Of Map Revision，LOMRs）。数字洪水保险费率图数据库是发布版纸质洪水保险费率图（Flood Insurance Rate Maps，FIRMs）所载洪水灾害信息的数字化地理空间版本。该数据集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，以及极低洪水风险区。国家洪水灾害图层数据源自洪水保险研究（Flood Insurance Studies，FISs）、此前发布的洪水保险费率图、为支撑洪水保险研究与洪水保险费率图开展的洪水灾害分析，以及现有可用的新型制图数据。上述洪水保险研究和洪水保险费率图均由美国联邦紧急事务管理署发布。数字洪水保险费率图数据的平面控制测量规范，与1:12000比例尺制图的相关要求保持一致。国家洪水灾害图层数据包含标准DFIRM数据集除S_Label_Pt和S_Label_Ld之外的所有图层。国家洪水灾害图层以各州或美国领地数据集的形式提供，每个州或领地数据集涵盖该数据集发布当日可用的全部数字洪水保险费率图及其对应的地图修订函。