A transect of wells is established on the marsh platform, perpendicular to the marsh edge. A total of 5 wells are dug to the depth of the water table under the marsh platform. Wells 1-4 are spaced approximately evenly within the first 6m of marsh edge with well 5 approximately 20m upland from the marsh edge. A water level logger, referred to as the tide gauge, (Onset HOBO U20 series) is placed at the river bottom directly in front of the transect . Individual water level loggers (Onset HOBO U20 series) are used in each well and they measure water height in terms of absolute pressure. Barometric pressure is measured above ground with an additional Onset HOBO U20 series water level logger to tease out the atmospheric pressure from water column pressure. Prior to deployment, each water level logger is sealed in protective plastic whirl-pak bags filled with freshwater, and calibrated to known water depths. Once in the field, water height measurements, in terms of absolute pressure, are recorded every 5 minutes. Pressure readings are uploaded from the HOBO water level loggers using HOBOware software which compensates for temperature, fluid density, and barometric pressure, then are converted to absolute water height above the river bottom. Data is QA/QC'd to ensure that the loggers report the same flood water elevation on the marsh surface. The surface elevation of the marsh as measured by the marsh water level loggers must match that of the gps'd surface elevation. Any corrections made to a particular logger data field (logger # Dc (m)) are reported in the Offset corr field (Offset corr logger # (m)).

Well Location Information:
Logger Well Height of Marsh Surface Above Creek Bottom (m) Horizontal Distance Upland of Creek Edge (m)
1 (tide gauge) 0
2 1 2.766 0.00
3 2 2.920 0.70
4 3 3.019 2.15
5 4 3.057 4.32
6 5 3.021 19.38

Logger 1 tide gauge located on river bottom.
Marsh wells 1-5, numbered consecutively moving upland.

NOTES AND COMMENTS: Due to occasional equipment malfunction, readings are not continuous throughout the field season. Times in EST.

See file 'RR finding marsh position GPS alternative 2013' to see how elevations determined in 2013 GPS software troubles during the 2013 year All values originally reported with approx 1.276m higher than all previous years Since loggers 8-12 were in the same positions for several years I used the average postions from 2011-2012 to get their elevations (see tab 'marsh elevation prev yrs' for details) Tide guage (logger 7) was in a different postion from 2012 so I used Vapp from logger 9 during a high tide (point where the water floods marsh surface) to calculate its height (see "Vapp ref log hgt' for details) Once I knew the Vapp (2.92) at logger 9 I subtracted the previous ave mash ht at 9 (in NADV88) from the 2.92 (ht relative to logger 7) to get the height of the ref logger to the marsh at logger 9 (-1.61m) Below I subtracted that elevation from logger 9 to get -0.71m