SIR2016-5029_cfwgoshor_3b: Flood Inundation Depth for a Flow of 21,450 cfs at the Gage Coast Fork Willamette River at Goshen, Oregon (Area of Uncertainty)

The domain of the model is as follows: Row River from Dorena dam to the confluence with the Coast Fork; Coast Fork from Cottage Grove dam to the confluence with the Middle Fork; Silk Creek from River Mile 1.7 to the confluence with the Coast Fork. The basis for these features is the Willamette Flood Insurance Study – Phase One (2013). The hydraulics and hydrology for the FIS were reused in the production of these polygons; the reports and information associated with the FIS are applicable to this product. The Digital Elevation Model (DEM) utilized for the Willamette FIS submittal was produced by combining multiple overlapping topographic surveys for the Middle Fork and Coast Fork of the Willamette River. This DEM was created from four sources: LiDAR of the Springfield area that was flown in 2008, LiDAR of Silk Creek that was flown in 2011, LiDAR of Fall Creek that was flown in 2012, and photogrammetry of the Middle Fork and Coast Fork of the Willamette River that was flown in 2004. In areas where no high-resolution elevation data were available, USGS National Elevation Dataset (NED) data were used to supplement the DEM. The shapefiles Hi_Res_Extents.shp and Low_Res_Extents.shp define the limits of these areas. The horizontal datum of the DEM is NAD 1983 State Plane-Oregon South HARN with units of International Feet (NAD83). The vertical datum of the elevation model is NAVD 1988 with units of international feet (NAVD-88). In addition, some areas show surveyed bathymetry within the channel. These can be noted by the sharp increase in apparent depth, creating a stripe across the depth grid when compared to the LiDAR data, which represents the water surface elevation at the time of the aerial data collection. Bridge decks are generally removed from DEMs as standard practice. Therefore, these features may be shown as inundated when they are not. An effort to clip flood extents on bridge decks was made, but judgement should be used when estimating the usefulness of a bridge during flood flow. Comparing the bridge to the surrounding ground can be more informative in this respect than simply looking at the bridge itself. The features and depth grids stop as the Coast Fork approaches the Middle Fork on the northern end of the reach. See cfwgoshOR_breach.shp for information regarding this file. This represents the depth grid for the 21,450 cfs profile.

该模型覆盖流域范围如下：罗河（Row River）从多雷纳大坝（Dorena dam）至与海岸支流（Coast Fork）的汇流处；海岸支流从科蒂奇格罗夫大坝（Cottage Grove dam）至与中支流（Middle Fork）的汇流处；锡尔克里克（Silk Creek）从河流里程1.7英里处至与海岸支流的汇流处。本数据集要素的编制依据为《威拉米特洪水保险研究——第一阶段（2013）》（Willamette Flood Insurance Study – Phase One (2013)）。本次生成的多边形复用了该洪水保险研究（FIS）中的水力与水文数据；与该FIS相关的报告及信息均适用于本产品。用于威拉米特FIS提交的数字高程模型（Digital Elevation Model, DEM），通过合并威拉米特河中游支流与海岸支流的多幅重叠地形测量数据生成。该DEM由四类数据源构建：2008年航测获取的斯普林菲尔德地区激光雷达（LiDAR）数据、2011年航测获取的锡尔克里克区域激光雷达数据、2012年航测获取的福尔溪（Fall Creek）区域激光雷达数据，以及2004年航测获取的威拉米特河中游支流与海岸支流的摄影测量数据。在无高分辨率高程数据的区域，采用美国地质调查局（United States Geological Survey, USGS）国家高程数据集（National Elevation Dataset, NED）数据补充DEM。Shapefile文件Hi_Res_Extents.shp与Low_Res_Extents.shp定义了上述高/低分辨率数据的覆盖范围。该DEM的水平基准面为NAD 1983 State Plane-Oregon South HARN，单位为国际英尺（NAD83）；垂直基准面为NAVD 1988，单位为国际英尺（NAVD-88）。此外，部分河道区域包含实测水深数据。此类区域可通过显著的深度突增特征识别：与激光雷达数据对比时，该突增会在深度网格上形成一条条纹，其对应航空数据采集时刻的水面高程。作为行业标准操作，桥梁桥面通常会从DEM中移除。因此，部分区域可能会被误标记为洪水淹没区域，但实际桥面并未被淹没。此前曾尝试裁剪桥梁桥面区域的洪水范围，但在评估洪水期间桥梁的通行可用性时，仍需结合人工判断。相较于仅观察桥梁本身，将桥梁与周边地面进行对比，能为该评估提供更有效的参考依据。本数据集的要素与深度网格，在海岸支流靠近河段北端的中支流汇流处终止。相关细节请参阅cfwgoshOR_breach.shp文件。本数据集对应21450立方英尺每秒（cfs）工况下的洪水深度网格。