DRAFT WILLAMETTE RIVER GREENWAY DESIGN PLAN <br />verification and adjustments to the TOB line in response to field conditions include: <br />• Aligning the TOB line exactly with the field-collected field data (points); or <br />• Aligning the TOB line with the riverside edge of the bike path on sites where the bike path exists. <br />Test sites were not selected to define the TOB line for the full corridor, but rather to verify the accuracy <br />of the mapped TOB line generated using LiDAR data in GIS. Along most of the river corridor, LiDAR data <br />indicates that TOB is consistent with the riverside shoulder of the bike path, where the path's edge abruptly <br />changes from predominately horizontal to predominantly vertical. Additionally, consultants observed the <br />bike path separating developed fill from a landform influenced by river hydrology and riparian flora and <br />floodplain detritus. <br />Using the riverside edge of bike path method as an adjustment where field-collected data points varied <br />from the mapped TOB line, consultants applied a general offset, riverside, from the bike path GIS layer (line <br />feature). Half the width of the standard bike path width was used as an offset, or --6 feet. This offset was <br />used as the adjusted TOB line within areas with an unclear interpretation of LiDAR hillshade data. <br />FINDINGS <br />The field investigation of test sites was conducted on the morning of October 12, 2021. Weather conditions <br />were partly cloudy, temperature of low 50 degrees, and no discernable precipitation. Following is a series <br />of tables for each sample site including observations, supporting information, methodology to determine <br />TOB line adjustment (if applicable), and findings. <br />Table 2.1 Test Site No. 1 <br />GPS Points Collected XX / XLF <br />Satellites Acquired 20 <br />Observations The test site is within an area frequently inundated by the water, <br />containing scattered riparian tree canopy, mid-story vegetation <br />like Salix sp. and landform character shaped by presence of water <br />and riverine systems. Detritus, woody debris caried by water, <br />and erosion observed along embankment adjacent to property <br />line. Field observed TOB line is close to or about a meter from <br />property lines of residential development to west. Unrelated to <br />TOB, consultants observed bank erosion caused by foot traffic <br />and deposits of yard debris. <br />Findings Presence of erosion was not used to determine TOB field data <br />point locations due to extent of foot traffic. Characteristics <br />including deposition of woody debris deposited by water, water <br />loving riparian vegetation and topography shaped by frequent <br />movement of water used instead of data points. GPS points <br />collected align with TOB line derived from GIS Hillshade data. <br />The mapped TOB line is accurate, and no adjustments are <br />proposed. <br />M WILLAMETTE RIVER GREENWAY CODE AMENDMENTS I CITY OF EUGENE 39 <br />