Flood Hazard Areas (FEMA)

The National Flood Hazard Layer (NFHL) data incorporates all Flood Insurance Rate Map (FIRM) databases published by the Federal Emergency Management Agency (FEMA), and any Letters of Map Revision (LOMRs) that have been issued against those databases since their publication date. The FIRM Database is the digital, geospatial version of the flood hazard information shown on the published paper FIRMs. The FIRM 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 (or 100-year) flood event, the 0.2-percent-annual-chance (or 500-year) flood event, and areas of minimal flood risk. The FIRM Database is derived from Flood Insurance Studies (FISs), previously published 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 FEMA. The NFHL is available as State or US Territory data sets. Each State or Territory data set consists of all FIRM Databases and corresponding LOMRs available on the publication date of the data set. The specification for the horizontal control of FIRM Databases is consistent with those required for mapping at a scale of 1:12,000. This file is georeferenced to the Earth's surface using the Geographic Coordinate System (GCS) and North American Datum of 1983. Date of last data update: 2026-04-24 This is official RLIS data. Contact Person: Alicia Wood [e-mail] 503-813-7561 RLIS Metadata Viewer: https://gis.oregonmetro.gov/rlis-metadata/#/details/1756 RLIS Terms of Use: https://rlisdiscovery.oregonmetro.gov/pages/terms-of-use

国家洪水灾害图层（National Flood Hazard Layer，NFHL）数据集整合了美国联邦紧急事务管理署（Federal Emergency Management Agency，FEMA）发布的所有洪水保险费率地图（Flood Insurance Rate Map，FIRM）数据库，以及自这些数据库发布之日起针对其出具的全部地图修订函（Letters of Map Revision，LOMRs）。
FIRM数据库是纸质版洪水保险费率地图所载洪水灾害信息的数字化地理空间版本。
该数据库用于展示支撑洪水风险数据编制的洪水风险信息及配套数据，所采用的核心风险分级包括年超越概率1%（即百年一遇）洪水事件、年超越概率0.2%（即五百年一遇）洪水事件，以及极低洪水风险区域。
FIRM数据库源自洪水保险研究（Flood Insurance Studies，FISs）、既往发布的洪水保险费率地图、为支撑洪水保险研究与洪水保险费率地图所开展的洪水灾害分析，以及可获取的新型测绘数据。洪水保险研究与洪水保险费率地图均由美国联邦紧急事务管理署发布。
国家洪水灾害图层以州或美国领地数据集的形式对外提供。每份州/领地数据集包含该数据集发布当日可用的全部FIRM数据库及其对应的地图修订函。
FIRM数据库的平面控制规范与1:12000比例尺测绘的要求保持一致。本文件采用地理坐标系（Geographic Coordinate System，GCS）与1983北美大地基准（North American Datum of 1983）完成地球表面地理配准。
最后数据更新日期：2026-04-24
本数据为官方RLIS数据。
联系人：Alicia Wood，电子邮箱：[e-mail]，联系电话：503-813-7561
RLIS元数据查看器：https://gis.oregonmetro.gov/rlis-metadata/#/details/1756
RLIS使用条款：https://rlisdiscovery.oregonmetro.gov/pages/terms-of-use