Annual Channel Geomorphology Cross-Section Surveys 2005-2012 in Roanoke, Virginia

Geomorphology monitoring sites at 15 locations along the Roanoke River in Salem and Roanoke, Virginia, represented riffle or pool habitats and were designed to facilitate repeated measuring at the same cross section over time. Local bench marks were installed at each site to provide both horizontal and vertical control. At a minimum, each site had two bench marks (designated BM) and two transect control marks (designated TC) that were tied together through a static survey-grade Global Positioning System (GPS) survey to establish control to the nearest centimeter. Annual cross-section topographic surveys were conducted during summer low-flow periods at the 15 geomorphology monitoring sites using a total station from 2005 to 2012 at each site. Floodplains, banks, channels, and water-surface elevations were surveyed, with each survey beginning on the floodplain a minimum of 50 ft from the active channel. Floodplain features were surveyed on 5-10-ft intervals and at major breaks in slope, channel banks were surveyed on 1-5-ft intervals, and the active channel was surveyed on 1-2-ft intervals to document channel changes with greater resolution. Most sites had one bank that was steeper and more vegetated than the other; bank steepness occasionally prevented complete surveying of the banks, in which case the survey was continued up the bank as far as possible. Pools were surveyed from a canoe when depths prohibited wading. Water-surface slope within 10 meters upstream and downstream of the cross section was surveyed most years for evaluation of changes in gradient.弗吉尼亚州塞勒姆与罗阿诺克两市境内的罗阿诺克河沿岸共设置15处地貌监测点位，覆盖浅滩（riffle）与深潭（pool）两类河流水生生境，旨在支持长期对同一河道断面开展重复测量工作。 所有监测点位均布设了本地水准基点（bench mark），以提供水平与垂直方向的测量控制基准。 每个点位至少设置2个水准基点（标注为BM）与2处断面控制标记（标注为TC），通过静态测量级全球定位系统（GPS）对上述标记进行联测，将控制精度锁定至厘米级。 2005年至2012年间，项目组于每年夏季枯水期使用全站仪对这15处地貌监测点位逐一开展河道断面地形测量。 每次断面测量均从距离主河道至少50英尺（ft）的河漫滩区域起始，测量范围涵盖河漫滩、岸坡、河道主体与水面高程。 河漫滩地貌以5至10英尺（ft）的间隔布设测点，并在主要坡度转折处加密采样；河道岸坡采用1至5英尺（ft）的间隔测量；主河道则以1至2英尺（ft）的间隔采集数据，以更高的分辨率记录河道形态变化。 多数点位的两侧岸坡存在明显差异：一侧更为陡峭且植被覆盖度更高。部分岸坡因坡度过陡无法完成全段测量，此时测量工作将尽可能沿坡向上延伸至可行范围。 当深潭（pool）水深超出涉水测量的极限时，测量工作将通过独木舟完成。 多数年份中，项目组还会对断面上下游10米范围内的水面坡度开展测量，用于评估河道比降的动态变化。