Comparing Methods and the Stability of Deep-Driven Rod Elevation Benchmarks and SETs in a Salt Marsh Environment

July 3, 2013 in Climate change/Sea level rise, Current Research Projects, Salt marsh, Sediments

IMG_2761PIs: Philippe Hensel, National Geodetic Survey
Galen Scott, National Geodetic Survey, University of RI
Jim Lynch, US Geological Survey
WBNERR Staff: Jim Rassman, Jordan Mora, Chris Weidman

Description: Sediment Elevation Tables (SETs) and benchmarks are used to measure change in marsh elevation with millimeter scale accuracy to determine sedimentation rates. This information, combined with accurate water level measures, can assess whether salt marshes are keeping up with sea level rise or risk being “drowned.” Traditionally SETs and benchmarks are installed by driving metal rods deep into the earth until they hit resistance. This can be difficult and costly as each 4’ length of rod is expensive. This project is investigating whether it is necessary to drive the rods that deep, or whether they are just as stable at, say, 20’ depth. Rods have been driven to different depths in the South Cape Beach salt marsh and are being “leveled” regularly – measured against a known point – to see if they have shifted. If not, this research could result in new standards for installation of this infrastructure which would save significant time and money. This is one of a growing number of projects in the new “Climate Change Observatory” in this marsh.