Flood Plain

Latest Study Effective Date 12/20/2019, Latest LOMR Effective Date 06/11/2019. 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. It is updated on a monthly basis. 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 flood event, the 0.2-percent-annual-chance 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 Dataum of 1983 (NSRS-2007).This layer is derived from NFHL Product ID NFHL_06073C, San Diego County-wide, Latest Study Effective Date 05/16/2012, Latest LOMR Effective Date 08/21/2015 with the additional County of San Diego, Department of Public Works, Flood Control Engineering-derived attribute FLOODPLAI.最新研究生效日期：2019年12月20日；最新地图修订函（Letters Of Map Revision, LOMR）生效日期：2019年6月11日。 国家洪水灾害图层（National Flood Hazard Layer, NFHL）数据集整合了联邦紧急事务管理局（Federal Emergency Management Agency, FEMA）发布的全部洪水保险费率地图（Flood Insurance Rate Map, FIRM）数据库，以及自各数据库发布之日起针对其出具的所有地图修订函（LOMR）。该数据集每月更新一次。 FIRM数据库是已发布纸质FIRM所载洪水灾害信息的数字化地理空间版本，呈现用于生成洪水风险数据的相关风险信息及配套支撑数据。其采用的主要风险分类包括年超越概率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。 FIRM数据库源自洪水保险研究（Flood Insurance Studies, FISs）、既往发布的FIRM、为支持FISs和FIRM开展的洪水灾害分析，以及可用的新测绘数据。FISs与FIRM均由FEMA发布。 NFHL以州或美国领地数据集的形式提供，每个州/领地数据集包含该数据集发布当日可用的全部FIRM数据库及对应的LOMR。 FIRM数据库的水平控制规范与1:12000比例尺测绘的相关要求保持一致。该文件采用地理坐标系（Geographic Coordinate System, GCS）与1983年北美大地基准面（North American Datum of 1983, NSRS-2007）完成地球表面地理配准。 本图层源自产品标识符为NFHL_06073C的全圣地亚哥县NFHL数据集，其最新研究生效日期为2012年5月16日，最新LOMR生效日期为2015年8月21日，并额外添加了由圣地亚哥县公共工程部防洪工程部门衍生而来的FLOODPLAI属性字段。