Examining Vertical Stability of Deep Rod Marks in Marshes Philippe Hensel 1, James Rassman 2, Jordan Mora 2, Chris Weidman 2, James Lynch 3, Christine Gallagher 1, Jarir Saleh 1 and Donald Cahoon 4 1 NOAA National Geodetic Survey 2 Massachusetts Department of Conservation and Recreation, Waquoit Bay National Estuarine Research Reserve 3 National Park Service Northeast Region 5 US Geological Survey, Patuxent Wildlife Research Center

Problem Statement 1 Wetland elevation change data using Surface Elevation Tables (SETs) rely on in situ vertical reference marks.

Problem Statement 1 Wetland elevation change data using Surface Elevation Tables (SETs) rely on in situ vertical reference marks. SET marks have varied over the past decade (pipes, rods), as have their installation methods (by hand, vibracorer, impact hammer, jackhammer)

Problem Statement 1 Wetland elevation change data using Surface Elevation Tables (SETs) rely on in situ vertical reference marks. SET marks have varied over the past decade (pipes, rods), as have their installation methods (by hand, vibracorer, impact hammer, jackhammer) Does installation method result in different vertical stability?

Problem Statement 2 Sea level change “Sentinel Sites” rely on a high accuracy local vertical control network Vertical control networks hard to find in marshes Railroad Bed T3 T4 T5 T1 T2 Patuxent River Railroad Bed Low intertidal SETs High intertidal SETs Tide station

Problem Statement 2 Sea level change “Sentinel Sites” rely on a high accuracy local vertical control network Vertical control networks hard to find in marshes Railroad Bed T3 T4 T5 T1 T2 Patuxent River Railroad Bed Low intertidal SETs High intertidal SETs Tide station But we have SET marks! Can SET marks be used for vertical control?

Problem Statement 2 Sea level change “Sentinel Sites” rely on a high accuracy local vertical control network Vertical control networks hard to find in marshes Wetland elevation change study sites contain SET marks Can SET marks be used as part of local vertical control networks? How often should one re-establish vertical connections to maintain network integrity?

A short history of the SET 1980’s – research into vertical wetland processes and rates focuses on vertical accretion 1990’s – Developed technique to include accretion and erosion: the SET

A short history of the SET 1980’s – research into vertical wetland processes and rates focuses on vertical accretion 1990’s – Developed technique to include accretion and erosion: the SET 2000 – Adopted sectional rod monument type for SET mark

A short history of the SET 1980’s – research into vertical wetland processes and rates focuses on vertical accretion 1990’s – Developed technique to include accretion and erosion: the SET 2000 – Adopted section rod monument type for SET mark 2010’s – NGS introduces modifications to SET instrument and reference mark

SETs and Sentinel Sites SETs are now being used to monitor elevation change at sentinel sites Can older SET technology be used in conjunction with sentinel site infrastructure? What is the effect of installation technique? Does installation technique lead to differential stability?

Waquoit Bay NERR Deep peat soils (300 feet?) Need to develop local vertical control network Local interest

Study Design I NGS 3D rod marks  reference marks – Compare insertion lengths among three techniques Manual hand held pile driver Bosch 11316EVS-type electric demolition hammer Gasoline-powered jackhammer – One 3D rod mark per wetland section (3)

Results 63.3’ 92.8’ 125.5’ All methods significantly different at P  0.02 n = 3

Study Design II 3D rod marks driven to known insertion lengths in wetland soil – 20 feet – 40 feet – 60 feet – 80 feet Perform high precision digital barcode leveling among all marks to monitor relative stability

Surveying in the Marsh RepDateCumulative Days 0Dec Dec days 2Dec days 3Jan days 4Feb days 5Mar days 6aMay 30 – Jun days 6b*Jul days 7Dec days * Connecting Sections 1 and 2 only

Leveling Statistics 90% of section misclosures  0.5 mm 70% of loop misclosures  0.5 mm

Results Spurious data connecting 3060 to 3001?

Potentially spurious data connecting 3060 to 3001

Possible error in section 3060 – 3001 (seen earlier)

Possible data error 3060 – 3001 on 12/28/2011

NGS Mark 555

Few sections show significant trends Section: FromToCoefficientsStandard Errort StatP-valueR Square

Preliminary Conclusions Different rod insertion techniques yield significantly different insertion lengths No clear evidence of initial settling No clear trend in (in)stability among insertion lengths Apparent movement of all marks within a section the result of site-specific movements or epoch-based measurement biases?