Making History at the VCU Rice Rivers Center
July 11, 2016
History was made at the VCU Rice Rivers Center. The first SET (Surface Elevation Table) was installed at 12:33 PM on Wednesday, May 25th 2016, and became a contributing partner investigating coastal wetland response to sea level rise in the NOAA Chesapeake Bay Sentinel Site Cooperative. With the help of A.W. Demeo (VIMS), Claudia Deeg (a VIMS intern), Ron Lopez (M.S. ENVS 2017), Melissa Davis (M.S. ENVS 2016), Chris Gatens (ENVS 2016/BIOL 2016) and Dr. Ed Crawford (VCU, Biology), two SETs were successfully installed within Harris Creek, initiating our long-term study. These two SETs (and others to follow) represent the first SETs installed in tidal forested wetlands within the James River watershed.
Ron Lopez, one of the graduate students for this project, offers the following explanation on what exactly this project will provide:
Accelerated rates of relative sea-level rise (RSLR) are predicted as a result of climate change. While tidal freshwater wetlands have been able to keep pace with RSLR via self-regulating mechanisms of sediment accretion in the past, it is not certain that they can continue to keep pace. Tidal forested freshwater wetlands, in particular, are understudied, and the understanding of their accretion dynamics is in its infancy. With this study, researchers hope to gain insight into rates of elevation change, and influencing factors, in tidal forested freshwater wetlands in the James River watershed, as well as to gauge the success of the Kimages Creek restoration in terms of sediment accretion.
What are SETs?
The SET is a device for measuring elevation change relative to a fixed benchmark. The instrument consists of a horizontal arm attached a vertical rod that is inserted into permanent benchmarks that have been installed in the substrate. Through the horizontal arm run nine pins that are lowered to the sediment surface to take measurements. Often used in conjunction with SETs are feldspar marker horizons, which are layers of white feldspar clay placed on the sediment surface that become buried as sedimentation occurs; sediment accretion can be measured by taking a core through the feldspar layer and measuring from the clay marker horizon to the sediment surface. Using the array of SETs coupled with feldspar marker horizons, researchers will be measuring elevation change, sediment accretion, and shallow subsidence occurring within the wetland sites. To date, 15 of the 18 first SETs (with the final three to be installed in James River National Wildlife Refuge July 12th) have been installed. The intention is to further expand the array of SETs to continue the advancement of this long-term study.
Where are the SETs?
For this research, observations and data collection will occur in three tidal forested freshwater wetlands: Harris Creek (at the Rice Rivers Center), Presquile National Wildlife Refuge, and James River National Wildlife Refuge. Additionally, researchers will be taking measurements in Kimages Creek (an ongoing restoration that previously existed as tidal forested freshwater wetland) in order to measure the success of the Kimages Creek restoration in the context of sediment accretion by comparing accretion measurements with those of the reference/ benchmark site at Harris Creek.
In order to gain insight into some of the factors that may govern variability in our measured rates of accretion and elevation change, researchers will be measuring predictor variables at each site to include: aboveground vegetation density, aboveground surface roughness, distance to sediment source, tidal inundation parameters, and suspended sediment concentration within each channel. Real Time Kinematic (RTK) base stations will be used to attain actual elevations at each site. The state-of-the-art RTK units are capable of sub-centimeter accuracy in the z-coordinate, allowing for precise elevation measurements.
In addition to bolstering the understanding of accretion dynamics in mature and restored tidal forested freshwater wetlands and allowing observation of elevation change in these ecosystems, this study marks a historical milestone for VCU Rice Rivers Center, as these SETs are the first installed in tidal forested freshwater wetlands in the James River watershed. Furthermore, the partnership with the national wildlife refuges and the incorporation of data into the NOAA Chesapeake Bay Sentinel Sites Cooperative sets a precedent of cooperative information sharing and adaption to sea-level rise.