Single-beam bathymetric survey of the French Broad River near the Interstate 26 bridge south of Asheville, NC – December 2020, Mid-Construction #1

In January 2020, the North Carolina Department of Transportation (NCDOT) began work on the Interstate 26 (I 26) highway widening project that involves a bridge crossing over the French Broad River (FBR) near Asheville, North Carolina. The U.S Geological Survey (USGS) in cooperation with the NCDOT conducted a pre-construction bathymetric survey of the streambed in June 2019 (Whaling and Wagner, 2021) within a one-kilometer reach of the FBR at the bridge construction site. A canoe-based repeat bathymetric survey was collected with a single-beam echosounder approximately 11 months after construction began, with the purpose to monitor geomorphological changes to the streambed and inform the NCDOT of potential impacts from construction activities. The survey extended from 300 meters (m) upstream to 700 m downstream from the bridge. Depth data were collected using a canoe-mounted CEESCOPE single-beam echosounder manufactured by CEE Hydrosystems. Position and elevation data were collected using an SBG Ellipse-D, a dual antenna Real-Time Kinematic (RTK) Inertial Navigation System (INS). The final dataset provides position data in three dimensions with units of meters supplied in a ?XYZ? file.� The data are projected in Universal Transverse Mercator (UTM) coordinate system, zone 17 north, horizontally referenced to the North American Datum of 1983 (NGS, 2018a), 2011 realization (NAD83 2011), and vertically referenced to the North American Vertical Datum of 1988 (NAVD88; NGS, 2018b).

2020年1月，北卡罗来纳州交通运输部（North Carolina Department of Transportation, NCDOT）启动了26号州际公路（Interstate 26, I-26）拓宽工程，该工程涉及在北卡罗来纳州阿什维尔附近跨越法国布罗德河（French Broad River, FBR）的桥梁建设项目。美国地质调查局（U.S. Geological Survey, USGS）与NCDOT合作，于2019年6月在该桥梁施工现场周边1公里范围的FBR河段内开展了河床前置水深测量（Whaling与Wagner, 2021）。工程启动约11个月后，研究团队采用单波束回声测深仪开展了基于独木舟的重复水深测量作业，旨在监测河床地貌变化，为NCDOT评估施工活动的潜在影响提供数据支撑。此次测量范围覆盖桥梁上游300米至下游700米的河段。水深数据由CEE Hydrosystems公司生产的CEESCOPE型单波束回声测深仪搭载于独木舟采集。位置与高程数据则采用SBG Ellipse-D双天线实时动态（Real-Time Kinematic, RTK）惯性导航系统（Inertial Navigation System, INS）采集。最终数据集以?XYZ?文件格式提供了单位为米的三维位置数据。该数据采用通用横轴墨卡托（Universal Transverse Mercator, UTM）坐标系17北分带进行投影，水平基准为1983北美大地基准面（North American Datum of 1983, NGS, 2018a）2011实现版本（NAD83 2011），垂直基准为1988北美垂直基准面（North American Vertical Datum of 1988, NAVD88; NGS, 2018b）。