SIR2016-5029_cfwgoshor_1: Flood Inundation Depth for a Flow of 12,000 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 12,000 cfs profile.

本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）从里程标记1.7英里处至与海岸支流的汇流处。
上述要素的编制依据为《威拉米特洪水保险研究——第一阶段（2013）》（Willamette Flood Insurance Study – Phase One (2013)）。本研究复用了该洪水保险研究（Flood Insurance Study，FIS）的水力学与水文学数据以生成上述多边形要素；与之相关的报告与信息同样适用于本数据集产品。
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由四类数据源构建而成：2008年航摄的斯普林菲尔德地区激光雷达（LiDAR）数据、2011年航摄的锡尔克里克激光雷达数据、2012年航摄的福尔溪激光雷达数据，以及2004年航摄的威拉米特河中游支流与海岸支流摄影测量数据。
对于缺乏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）补充DEM。形状文件（shapefile）Hi_Res_Extents.shp与Low_Res_Extents.shp划定了上述补充数据的覆盖范围。
该DEM的水平基准为NAD 1983俄勒冈州南部州平面高分辨率大地基准（NAD 1983 State Plane-Oregon South HARN），单位为国际英尺（NAD83）；高程模型的垂直基准为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可见，此类区域的表观水深会出现显著跃升，在水深网格中形成条带，该条带对应航空数据采集时刻的水面高程。
作为常规操作，DEM通常会移除桥面高程数据。因此，部分区域可能会将非淹没状态的桥面显示为淹没状态。本次数据集已尝试对桥面区域的洪水范围进行裁剪，但在评估桥梁在洪水工况下的可用性时，仍需结合实际判断。相较于仅观察桥梁本身，将桥梁与周边地面进行对比，能更准确地反映该区域的实际情况。
本数据集的要素与水深网格在海岸支流接近中游支流的河段北端处终止。相关文件信息可参考cfwgoshOR.shp。本数据集对应12000立方英尺每秒（cubic feet per second，cfs）流量过程的水深网格。