Geospatial datasets and model for the flood-inundation study of the Wabash River near the Interstate 64 Bridge near Grayville, Illinois

A two-dimensional model and digital flood-inundation maps were developed for a 30-mile reach of the Wabash River near the Interstate 64 (I-64) Bridge near Grayville, Illinois. The flood-inundation maps, which can be accessed through the U.S. Geological Survey (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 Wabash River at Mount Carmel, Ill (USGS station number 03377500). 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 (AHPS) at http://water.weather.gov/ahps/, which also forecasts flood hydrographs at this site (NWS AHPS site MCRI2). The NWS AHPS forecasts peak stage information that may be used with the maps developed in this study to show predicted areas of flood inundation. Flood elevations were computed for the Wabash River reach by means of a two-dimensional, finite-volume numerical modeling application for river hydraulics. The hydraulic model was calibrated by using global positioning system measurements of water-surface elevation and the current stage-discharge relation at both USGS streamgage 03377500, Wabash River at Mount Carmel, Ill., and USGS streamgage 03378500, Wabash River at New Harmony, Indiana. The calibrated hydraulic model was then used to compute 27 water-surface elevations for flood stages at 1-foot (ft) intervals referenced to the streamgage datum and ranging from less than the action stage (9 ft) to the highest stage (35 ft) of the current stage-discharge rating curve. The simulated water-surface elevations were then combined with a geographic information system digital elevation model, derived from light detection and ranging data, to delineate the area flooded at each water level. The availability of these maps, along with information on the internet regarding current stage from the USGS streamgage at Mount Carmel, Ill., and forecasted stream stages from the NWS AHPS, provides emergency management personnel and residents with information that is critical for flood-response activities such as evacuations and road closures, as well as for postflood recovery efforts.

针对伊利诺伊州格雷维尔附近64号州际公路（Interstate 64, I-64）大桥周边30英里长的沃巴什河河段，本研究研发了二维水动力模型与数字洪水淹没图。该洪水淹没图可通过美国地质调查局（U.S. Geological Survey, USGS）洪水淹没制图科学网站（http://water.usgs.gov/osw/flood_inundation/）获取，其展示了对应伊利诺伊州芒特卡梅尔沃巴什河美国地质调查局水文测站（USGS站点编号：03377500）选定水位（水位计读数）的洪水范围与水深估算结果。
该水文测站的准实时水位数据可通过互联网从美国地质调查局国家水信息系统（http://waterdata.usgs.gov/），或美国国家气象局（National Weather Service, NWS）高级水文预报服务（Advanced Hydrologic Prediction Service, AHPS）网站（http://water.weather.gov/ahps/）获取，后者还可预报该站点的洪水过程线（NWS AHPS站点编号：MCRI2）。美国国家气象局高级水文预报服务发布的峰值水位数据，可结合本研究研发的淹没图展示预测的洪水淹没范围。
本研究针对该沃巴什河河段，采用二维有限体积法河流水动力数值模型计算了洪水水位。该水动力模型通过以下方式完成率定：采用全球定位系统（Global Positioning System, GPS）测得的水面高程数据，以及美国地质调查局两个水文测站——伊利诺伊州芒特卡梅尔沃巴什河站（USGS站点编号：03377500）与印第安纳州纽黑莫尼沃巴什河站（USGS站点编号：03378500）的现行水位-流量关系。
率定完成后的水动力模型被用于计算27个洪水水位对应的水面高程，水位间隔为1英尺（ft），以水文测站基准面为参照，取值范围从低于警戒水位（9 ft）至现行水位-流量关系曲线的最高水位（35 ft）。将模拟得到的水面高程与基于激光雷达（Light Detection and Ranging, LiDAR）数据生成的地理信息系统（Geographic Information System, GIS）数字高程模型相结合，即可勾画出各水位对应的淹没区域。
该批淹没图结合互联网上可获取的伊利诺伊州芒特卡梅尔沃巴什河美国地质调查局水文测站实时水位数据，以及美国国家气象局高级水文预报服务发布的预报水位数据，可为应急管理人员与居民提供关键信息，用于洪水应急响应（如人员疏散与道路封闭）以及灾后恢复工作。