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 5m 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 10 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) 0.00
2 1 2.848
3 2 3.006
4 3 3.058
5 4 3.066
6 5 3.091

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.

Procedure for GPS error corrections for 2013 and 2014 loggers
 
For an unknown reason, GPS data for the 2013-2014 years has an offset from all previous years.
Below is the procedure I used to account for this offset.
PIE has been taking GPS measurements at these sites for many years.
The same well holes were often used for multiple years (often only the underwater ref logger changed).
I averaged the marsh heights from 2011 and 2012 (which the GPS data are good).
I subtracted the 2014 values from the average 2011/2012 values.
There was a 1.31m difference between them.
To figure the correct marsh height I subtracted 1.31 from each of the 2014 values.
The corrected values are what is used in the 2014 calculations.

For Typha there was an additional factor to consider because the bank collapsed over the winter of 2012 . We Dug two new wells between what was previously known as well T5 and T4 (2012 and prior) Relabelled wells in a poor way! 2012 wells T1 and T2 are gone Well T1 for 2014 is the same well as T3 in 2012, T2=T4, T3 and T4 are new, and T5 is the same as 2012 T5 See field notebook for claification Mar 23, 2013