Depth grids of the flood-inundation maps for the Meramec River at Valley Park, Missouri, 2017

Digital flood-inundation maps for a 9.1-mile reach of the Meramec River near Valley Park, Missouri, were created by the U.S. Geological Survey (USGS) in cooperation with the US Army Corps of Engineers, St. Louis Metropolitan Sewer District, Missouri Department of Transportation, Missouri American Water, and Federal Emergency Management Agency Region 7. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Meramec River at Valley Park, Missouri (station number 07019130). Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also forecasts flood hydrographs at this site. Flood profiles were computed for the stream reach by means of a one-dimensional step-backwater model. The model was calibrated using the current stage-discharge relation at the Meramec River near Eureka streamgage and documented high-water marks from the floods of December 30, 2015. The hydraulic model was then used to compute 44 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum and ranging from 11 ft or near bankfull to 54 ft, which exceeds the stage that corresponds to the maximum recorded peak flow. The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging (lidar) data having a 0.5-ft vertical accuracy and 3.28-ft horizontal resolution) to delineate the area flooded at each water level. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post flood recovery efforts.

美国地质调查局（U.S. Geological Survey, USGS）联合美国陆军工程兵团（U.S. Army Corps of Engineers）、圣路易斯都会区下水道区、密苏里州交通部、密苏里美国水务公司以及联邦紧急事务管理局第7区，编制了密苏里州谷帕克附近梅拉梅克河9.1英里河段的数字洪水淹没地图。此类洪水淹没地图可通过美国地质调查局洪水淹没制图科学网站（http://water.usgs.gov/osw/flood_inundation/）获取，其展示了对应密苏里州谷帕克梅拉梅克河美国地质调查局水文测站（streamgage，站号07019130）选定水位的洪水范围与水深估算值。该测站的近实时水位数据可从美国地质调查局国家水信息系统（http://waterdata.usgs.gov/）或国家气象局（National Weather Service, NWS）高级水文预报服务平台（http://water.weather.gov/ahps/）获取，后者还可预报该站点的洪水流量过程线。研究人员采用一维阶梯回水模型（one-dimensional step-backwater model）计算了该河段的洪水水面线，该模型以尤卡附近梅拉梅克河水文测站当前的水位-流量关系以及2015年12月30日洪水记录的高水位标记完成率定。随后，该水力模型以该水文测站基面为基准，针对1英尺（ft）间隔的水位等级计算了44条水面线，水位范围从接近堤岸满水位的11英尺至超出有记录以来最大峰值流量对应水位的54英尺。研究人员将模拟得到的水面线与地理信息系统（Geographic Information System, GIS）数字高程模型（源自垂直精度0.5英尺、水平分辨率3.28英尺的激光雷达（light detection and ranging, lidar）数据）相结合，勾勒出各水位对应的淹没区域。此类地图的可获取性，搭配美国地质调查局水文测站提供的当前水位信息以及国家气象局预报的高水位预报信息，可为应急管理人员与居民提供至关重要的信息，用于洪水应对工作（如人员疏散与道路封闭）以及灾后恢复工作。