Sawyer Mill Dam Removal Upper Impoundment Survey Transects (2019 and 2020)

These are the calculations for creating the survey elevation profiles pre-/post-dam removal in the Evans et al. Sawyer Mill dam removal reservoir response manuscript. The plots were made using the “Points to Line”, “Split Line at Point”, and “Calculate Geometry Attributes” tools in ArcGIS Pro to get the distances of the surveyed points along the transect lines. To calculate the length (LENGTH_GEODESIC option) of the lines in the “Calculate Geometry Attributes” tool, the coordinate system parameter was set to NAD 1983 (2011) StatePlane New Hampshire FIPS 2800 and measured in meters. Digital surface model (DSM) values were extracted from the same X/Y locations of the conventional survey measurements on the corresponding drone DSMs for each survey time to visualize differences between the conventional and drone survey transects and influences of refraction and vegetation in the drone values. 2019 measurements were post-lower dam removal and pre-upper dam removal while the 2020 measurements were post-both dam removals. The survey measurements were collected either on or within a couple days of the corresponding drone flight dates, which are used for the cross-section legends. Sometimes the beginning or end transect stake was unable to be surveyed every year due to poor satellite signal under trees (points were surveyed with a Topcon Hiper Lite+). If that was the case, another point representing the beginning stake was added to that year’s transect from a different year where the beginning stake was successfully surveyed. Elevation values correspond to NAVD88 in meters. The terrain columns contain transcribed field notes from the survey notebooks. Please see the spreadsheet and manuscript for additional information.<br>These materials were made using resources from an NSF EPSCoR funded project “RII Track-2 FEC: Strengthening the scientific basis for decision-making about dams: Multi-scale, coupled-systems research on ecological, social, and economic trade-offs” (a.k.a. "Future of Dams"). Support for this project is provided by the National Science Foundation’s Research Infrastructure Improvement NSF #IIA-1539071. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.<br>