Surface Elevation Tables (SETs) were installed in 2009 and 2010 using permanent, deep rods driven down into the soil with a demolition hammer, typically about 60-80 feet. The top of the rod lies near the sediment surface, with a receiver end. A Surface Elevation Table is a portable mechanical leveling device that attaches to the receiving end at the top of the deep rod. The SET arm includes a bubble level and a notched collar that allows for the arm to be aligned precisely and repeatedly in the cardinal directions. SETs were installed as triplicates in Reference, Phase II, and as north-south pairs in the 2009 restoration area (Units 1-4). Each SET location was read repeatedly at regular, at least annual intervals. Reading SETs consisted of measurements for nine pins facing the four cardinal directions for a total of 36 measurements per SET, per sampling event. Each pin was measured to the nearest millimeter.

Surface Elevation Tables and Marker Horizon (collectively SET-MH) datasets provide a unique opportunity to evaluate tidal marsh accretion rates compared with current and projected sea-level rise. SET is a tool that allows for accurate and repeatable measurements of marsh elevation, while Marker Horizon allows for the measurement of sediment that has deposited on top of the feldspar marker. SETs are deep rod benchmarks with an attachment for a portable leveling device (arm) at fixed directions. The distance from the fixed arm to the marsh surface is measured by lowering a set of pins (usually nine) from the SET to the marsh surface, providing a repeatable and accurate measurement of elevation change. Marker horizon data measure the amount of sediment that is deposited onto the marsh surface, is a layer of white feldspar clay applied to a 0.5x0.5m quadrats associated with each SET. Marker horizons are measured by extracting a plug from the marsh surface using a knife or cryo-core, and measuring the sediment deposited on top of the layer. Together, repeated measurements of SET-MH data separates surface deposition from shallow subsurface processes (e.g., root growth or shallow soil compaction). The ability of a tidal marsh to keep up with sea-level rise was largely due to relative sediment load and to a smaller degree it’s position within the tidal frame.

Surface Elevation Tables and Marker Horizon (collectively SET-MH) datasets provide a unique opportunity to evaluate tidal marsh accretion rates compared with current and projected sea-level rise. SET is a tool that allows for accurate and repeatable measurements of marsh elevation, while Marker Horizon allows for the measurement of sediment that has deposited on top of the feldspar marker. SETs are deep rod benchmarks with an attachment for a portable leveling device (arm) at fixed directions. The distance from the fixed arm to the marsh surface is measured by lowering a set of pins (usually nine) from the SET to the marsh surface, providing a repeatable and accurate measurement of elevation change. Marker horizon data measure the amount of sediment that is deposited onto the marsh surface, is a layer of white feldspar clay applied to a 0.5x0.5m quadrats associated with each SET. Marker horizons are measured by extracting a plug from the marsh surface using a knife or cryo-core, and measuring the sediment deposited on top of the layer. Together, repeated measurements of SET-MH data separates surface deposition from shallow subsurface processes (e.g., root growth or shallow soil compaction). The ability of a tidal marsh to keep up with sea-level rise was largely due to relative sediment load and to a smaller degree it’s position within the tidal frame.

SET-MH were installed in 2009 and 2010 with three replicates in Reference and Phase II and with two replicates (north-south) pairs in the 2009 restoration area (Units 1-4). SET-MH were read repeatedly at regular, at least annual intervals. Reading SETs consisted of measurements for nine pins facing the four cardinal directions for a total of 36 measurements per SET, per sampling event. Marker Horizons consisted of a marker, usually white feldspar clay, so that the sediment that accumulated on top of the marker would be visible and measurable to the nearest millimeter. Together, SET-MH provide information on surface elevation changes due to surface accretion (MH) compared to changes that may be due to subsurface processes (such as root growth or groundwater swelling).

Surface elevation tables with marker horizons (SET-MH) measure millimeter-scale changes in elevation over time. A combination of pin measurements (elevation change) and surface deposition measurements (marker horizon) is used to distinguish elevation changes due to belowground and aboveground processes. SET-MHs were installed in 2016 and were measured quarterly across five tidal marshes (Petaluma marsh, San Pablo Bay National Wildlife Refuge, Rush Ranch, Browns Island, and Miners Slough).

Surface elevation tables with marker horizons (SET-MH) measure millimeter-scale changes in elevation over time. A combination of pin measurements (elevation change) and surface deposition measurements (marker horizon) is used to distinguish elevation changes due to belowground and aboveground processes. SET-MHs were installed in 2016 and were measured quarterly across five tidal marshes (Petaluma marsh, San Pablo Bay National Wildlife Refuge, Rush Ranch, Browns Island, and Miners Slough).

GPS horizontal and vertical position data were collected on the Nisqually River, McAllister Creek and Nisqually River Delta to survey in water surface, instrumentation and delta structures for to reference North American Vertical Datum 1988 (NAVD88). These data are housed in .csv file named “Nisqually GPS Data” and are sorted by date and time. The position data are grouped by data collection methods Point and Topo. Point method collected position data for 180 seconds and was used to survey surface water and instrumentation elevation. Topo method collected position point data for 1 second and was used for surveying delta bathymetry elevation. Data were collected using the available RTN-GPS network provided by the Washington State Reference Network and using a Trimble R8 GPS antenna mounted on a 2-meter rod. Position data are labeled with descriptors such as “WS” (water surface) or “Delta” which refer to the feature surveyed. Check-in/check-out procedures were satisfied using reference marker Station: pid_sy0708. Two check-in orthometric heights were collected (60.05 and 60.10 m) and following point and topo data collection one check-out orthometric height (60.04 m) was collected. Bathymetric data (Topo method) was collected across the Nisqually River Delta starting at the left bank of McAllister Creek (MC2) and ended on the right bank of tidal channel D4. A total of 2,505 positions were surveyed using the topo method and positions were labeled as “delta-trav###”. Delta elevation ranged from 3.44 to -1.64 meters (NAVD88). Rod and antenna were held at a fixed level marked on both upper rod and technician for maintaining a constant 2 meter height above the walking surface. The bottom half of the rod was removed during topo data collection for ease of walking to avoid rod tip drag and keeping an even pace along the delta structures. Tidal channel bathymetry data consists of transects between banks with position names containing the tidal channel name and distance upstream or downstream of deployed sensor. Only D4 and D3 tidal channel bathymetric data sets were collected. Both D3 (Station ID: “les”) and D4 (Station ID: “are3”) had four tidal channel bathymetry transects collected which consisting of a 10 and 20 meter upstream and downstream of deployed sensor transects. Point data were collected at sites with sensors collecting water depth (WL) time-series data. GPS data was collected by holding the rod/antenna unit at a bubble-level static positioned for 3 minutes (180 epochs) during data collection. Point data were water surface elevations which were used to provide offsets for converting recorded water level (WL) data by sensors to referenced NAVD88.

Tabular datasets in text format (.CSV) containing data on marsh surface elevation, accretion, and sampling station information. The datasets were used in a custom R Package (https://irma.nps.gov/DataStore/Reference/Profile/2296626) containing code, data, and documentation to: • Determine trends for each Sampling Station, Site and Park using a GLMM or GAMM based on elevation and accretion data over the full length of the dataset. • Compare elevation and accretion trends to each other for each Sampling Station and Site, as well as to local rates of sea level rise (SLR), • Provide guidance based for when to consider analyzing the SET dataset over shorter time periods, as well as compare accretion and elevation linear trends based on fall and spring sampling dates to determine if sampling frequency can be limited to once per year.

An upward-looking acoustic Doppler velocity meter (ADVM, SonTek SW, 3.0 MHz) located in a tidal channel of the Nisqually River Delta at site D3 (N 47d 05’ 36.5”/W 122d 42’ 42.9”) measured water level and current velocity at 15-minute intervals from April 1, 2017 to July 20, 2017 (80.9 days, excluding missing periods). This site is in a tidal channel at a levee breach where flow is tidally influenced. The water depth of the sensor ranged from 0.05 to 3.04 m and may have been lower during periods of extreme low tide. The elevation (NAVD88) of the ADVM sensor was surveyed by RTN-GPS. The offset to convert all water depth time-series data to water surface elevation (NAVD88) is 0.47 meters. The instrument temperature ranged from 7.2 to 23.0 degrees C but may be bias during periods of low tide due to solar heating of the submerged instrument. The mean downstream velocity component (Vx) ranged from -0.81 to 0.81 m/s. The mean vertical velocity component (Vy) ranged from -0.40 to 0.49 m/s and signal to noise ratio ranged from 21.3 to 82.8 dB. The ADVM measured the water-velocity profile using a dynamic boundary adjustment mode allowing up to 10 velocity measurements in the water-column profile. Time-series gaps of 15-minutes or more occurred when the instrument was offline, when error thresholds were exceeded, or when the water level in the channel dropped below the elevation of the sensor during periods of extreme low tide. Discrete discharge data at this site are available at: https://waterdata.usgs.gov/wa/nwis/inventory/?site_no=12081525&agency_cd=USGS&

An upward-looking acoustic Doppler velocity meter (ADVM, SonTek SW, 3.0 MHz) located in a tidal channel of the Nisqually River Delta at site D3 (N 47d 05’ 36.5”/W 122d 42’ 42.9”) measured water level and current velocity at 15-minute intervals from April 1, 2017 to July 20, 2017 (80.9 days, excluding missing periods). This site is in a tidal channel at a levee breach where flow is tidally influenced. The water depth of the sensor ranged from 0.05 to 3.04 m and may have been lower during periods of extreme low tide. The elevation (NAVD88) of the ADVM sensor was surveyed by RTN-GPS. The offset to convert all water depth time-series data to water surface elevation (NAVD88) is 0.47 meters. The instrument temperature ranged from 7.2 to 23.0 degrees C but may be bias during periods of low tide due to solar heating of the submerged instrument. The mean downstream velocity component (Vx) ranged from -0.81 to 0.81 m/s. The mean vertical velocity component (Vy) ranged from -0.40 to 0.49 m/s and signal to noise ratio ranged from 21.3 to 82.8 dB. The ADVM measured the water-velocity profile using a dynamic boundary adjustment mode allowing up to 10 velocity measurements in the water-column profile. Time-series gaps of 15-minutes or more occurred when the instrument was offline, when error thresholds were exceeded, or when the water level in the channel dropped below the elevation of the sensor during periods of extreme low tide. Discrete discharge data at this site are available at: https://waterdata.usgs.gov/wa/nwis/inventory/?site_no=12081525&agency_cd=USGS&