General Structures

<p>The National Flood Hazard Layer (NFHL) is a geospatial database that
contains current effective flood hazard data. FEMA provides the flood
hazard data to support the National Flood Insurance Program. You can use
the information to better understand your level of flood risk and type
of flooding. The simplest way for you to access the flood hazard data,
including the NFHL, is through <a href='https://msc.fema.gov/'>FEMAs Map Service Center (MSC)</a>.</p><p>If you want to explore the current digital effective flood hazard data in a map, the best tool to use is the <a href='https://msc.fema.gov/nfhl'>NFHL Viewer</a>. From the NFHL Viewer, you may view, download, and print flood maps for your location.</p><p>The NFHL is made from effective flood maps and Letters of Map Change
(LOMC) delivered to communities. NFHL digital data covers over 90
percent of the U.S. population.  New and revised data is being added
continuously. If you need information for areas not covered by the NFHL
data, there may be other <a href='https://msc.fema.gov/portal/resources/productsandtools'>FEMA Flood Hazard Products and Services</a> which provide coverage for those areas.</p><p>A list of the types of data available in the NFHL and information about other ways to access the NFHL may be found in the <a href='https://hazards.fema.gov/femaportal/wps/portal/NFHLWMS'>NFHL GIS Services User Guide</a>.</p><p>If you need more information about individual tables in the NFHL, the FIRM Database Technical Reference, found at FEMA’s <a href='https://www.fema.gov/media-library/assets/documents/34519'>Technical References</a>, includes those details.</p><p>For step-by-step instructions on how to read a flood map, you may view the <a href='https://www.fema.gov/media-library/assets/documents/7984'>How to Read a Flood Insurance Rate Map Tutorial</a>.</p>For more information, please visit the <a href='https://msc.fema.gov/portal/home' target='_blank'>FEMA Flood Map Service Center</a>.

国家洪水灾害图层（National Flood Hazard Layer，NFHL）是一款收录现行有效洪水灾害数据的地理空间数据库（geospatial database）。联邦紧急事务管理局（Federal Emergency Management Agency，FEMA）提供此类洪水灾害数据，以支撑国家洪水保险计划（National Flood Insurance Program）的运行。您可借助该信息更好地评估自身面临的洪水风险等级与洪水类型。获取包括NFHL在内的洪水灾害数据的最简途径，是通过<a href="https://msc.fema.gov/">FEMA地图服务中心（FEMA's Map Service Center，MSC）</a>。
若您希望通过地图可视化探索现行数字版有效洪水灾害数据，最佳工具为<a href="https://msc.fema.gov/nfhl">NFHL查看器（NFHL Viewer）</a>。通过NFHL查看器，您可查看、下载并打印所属区域的洪水地图。
NFHL由提交至各社区的有效洪水地图与地图变更函（Letters of Map Change，LOMC）整合构建而成。该数字数据集覆盖了美国超过90%的常住人口。新数据与经修订的数据正持续更新入库。若您所需的信息所在区域未被NFHL覆盖，可通过<a href="https://msc.fema.gov/portal/resources/productsandtools">FEMA洪水灾害产品与服务</a>获取此类区域的相关数据。
NFHL支持的数据类型清单，以及其他获取NFHL的途径，均可在<a href="https://hazards.fema.gov/femaportal/wps/portal/NFHLWMS">NFHL地理信息系统（Geographic Information System，GIS）服务用户指南（NFHL GIS Services User Guide）</a>中查阅。
若您需要了解NFHL中各数据表的详细信息，可查阅FEMA官网发布的<a href="https://www.fema.gov/media-library/assets/documents/34519">洪水保险费率地图（Flood Insurance Rate Map，FIRM）数据库技术参考手册</a>，其中包含了此类细节内容。
如需获取阅读洪水地图的分步操作指南，您可查看<a href="https://www.fema.gov/media-library/assets/documents/7984">《洪水保险费率地图阅读教程》</a>。
如需获取更多相关信息，请访问<a href="https://msc.fema.gov/portal/home" target="_blank">FEMA洪水地图服务中心（FEMA Flood Map Service Center）</a>。