SIR2016-5029_cfwgoshor_4: Flood Inundation Depth for a Flow of 27,900 cfs at the Gage Coast Fork Willamette River at Goshen, Oregon

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.shp for information regarding this file. This represents the depth grid for the 27,900 cfs profile.

本模型覆盖的流域范围如下：多里纳大坝至与海岸支流汇流处的罗河；科蒂奇格罗夫大坝至与中支流汇流处的海岸支流；里程标1.7处至与海岸支流汇流处的丝绸溪。上述空间要素的编制依据为《威拉米特洪水保险研究——第一阶段（2013）》（Willamette Flood Insurance Study – Phase One (2013)）。本次多边形数据的制作复用了该洪水保险研究（FIS）中的水力学与水文学数据，该研究配套的报告与信息同样适用于本产品。用于提交威拉米特洪水保险研究的数字高程模型（Digital Elevation Model, DEM），通过整合威拉米特河中游支流与海岸支流的多份重叠地形测量数据生成。该DEM包含四类数据源：2008年航拍的斯普林菲尔德地区激光雷达（LiDAR）数据、2011年航拍的丝绸溪激光雷达数据、2012年航拍的福尔溪激光雷达数据，以及2004年航拍的威拉米特河中游支流与海岸支流摄影测量数据。在无高分辨率高程数据的区域，本DEM补充采用了美国地质调查局（United States Geological Survey, USGS）国家高程数据集（National Elevation Dataset, NED）的数据。形状文件Hi_Res_Extents.shp与Low_Res_Extents.shp界定了上述高分辨率数据的覆盖范围。该DEM的水平基准面为NAD 1983俄勒冈州南部州平面HARN，单位为国际英尺（NAD83）；该高程模型的垂直基准面为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。与激光雷达数据对比时，此类区域会在深度网格中呈现出显著的深度跃升条纹，其对应航空数据采集时刻的水面高程。作为行业标准操作流程，桥面高程通常会从DEM中移除，因此可能出现桥面未被淹没却被标记为淹没的情况。虽已尝试对桥面区域的洪水范围进行裁剪处理，但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，将其与周边地面高程进行对比，能更有效地辅助相关判断。本数据集的空间要素与深度网格在研究河段北端，即海岸支流靠近中支流的汇流处终止。有关该文件的详细信息，请参阅cfwgoshOR.shp。本数据集对应27900立方英尺每秒（cfs）流量剖面的深度网格。