Delta-X: Bed and Suspended Sediment Grain Size, MRD, LA, USA, 2021, Version 2

This dataset provides sediment concentration and grain size distribution measurements from suspended and bed sediment samples collected in the Atchafalaya and Terrebonne River Basins as part of the Delta-X Spring campaign between March 24 to April 2, 2021 and Delta-X Fall campaign between August 17-25, 2021. During the field campaign, samples were collected in the main distributary channels and the interior of Mike Island in the Wax Lake Delta, Louisiana and at site CRMS0421 inside the Terrebonne River Basin. Sediment samples were collected from a boat using a Van Dorn sampler (for suspended sediment samples) or a Ponar bed sampler (for bed samples). Suspended sediment samples were collected from a boat drifting at approximately the same velocity as the water flow. One sample was collected per drift. Bed samples were collected in a similar fashion. Data includes measurements of sediment grain size, total sediment concentration, as well as water temperature, velocity, salinity, and depth. This Version 2 includes the initial release of Fall 2021 data and an update to the Version 1 (Spring 2021) data file in which an error in the data was resolved.

In this Version 2, an error in Version 1 of the Spring 2021 file was resolved. This error was introduced during processing by ORNL DAAC which caused some 'date_time' values to be associated with incorrect rows of data. Version 2 also includes the initial release of Fall 2021 data.

This dataset contains two data files in comma separated values (*.csv) format.

This dataset provides sediment concentration and grain size distribution measurements from suspended and bed sediment samples collected in the Atchafalaya and Terrebonne River Basins as part of the Delta-X Spring campaign between March 24 to April 2, 2021 and Delta-X Fall campaign between August 17-25, 2021. During the field campaign, samples were collected in the main distributary channels and the interior of Mike Island in the Wax Lake Delta, Louisiana and at site CRMS0421 inside the Terrebonne River Basin. Sediment samples were collected from a boat using a Van Dorn sampler (for suspended sediment samples) or a Ponar bed sampler (for bed samples). Suspended sediment samples were collected from a boat drifting at approximately the same velocity as the water flow. One sample was collected per drift. Bed samples were collected in a similar fashion. Data includes measurements of sediment grain size, total sediment concentration, as well as water temperature, velocity, salinity, and depth. This Version 2 includes the initial release of Fall 2021 data and an update to the Version 1 (Spring 2021) data file in which an error in the data was resolved. 

Project: Delta-X

The Delta-X mission is a 5-year NASA Earth Venture Suborbital-3 mission to study the Mississippi River Delta in the United States, which is growing and sinking in different areas. River deltas and their wetlands are drowning as a result of sea level rise and reduced sediment inputs. The Delta-X mission will determine which parts will survive and continue to grow, and which parts will be lost. Delta-X begins with airborne and in-situ data acquisition and carries through data analysis, model integration, and validation to predict the extent and spatial patterns of future deltaic land loss or gain.

Related dataset

Castaneda, E., A.I. Christensen, M. Simard, D.J. Jensen, R. Twilley, and R. Lane. 2020. Pre-Delta-X: Total Suspended Solids of Surface Water across MRD, LA, USA, 2015-2016. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1802.

• Contains total suspended solids measurements of surface water in the MRD during Pre-Delta-X in 2020.

Nghiem, J., G. Salter, and M.P. Lamb. 2022. Delta-X: Bed and Suspended Sediment Grain Size, Wax Lake Delta, LA, USA, 2021. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2061

• Version 1 of this dataset (superseded).

Acknowledgement

This work was supported by NASA Earth Venture Suborbital-3 Program (grant NNH17ZDA001N-EVS3: Delta-X) and Research and Technology Development at NASA's Jet Propulsion Laboratory (Strategic R&TD FY17–19).

Spatial Coverage: Atchafalaya and Terrebonne Basins, Mississippi River Delta (MRD) floodplain, southern coast of Louisiana, USA

Spatial Resolution: Point

Temporal Coverage: 2021-03-24 to 2021-08-25

Temporal Resolution: One-time measurements

Site Boundaries: Latitude and longitude are given in decimal degrees.

Site	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude
Atchafalaya and Terrebonne Basins	-91.45234	-90.82263	29.70441	29.17151

Data File Information

This dataset contains two files in comma-separated values (.csv) format:

• DeltaX_GrainSizeDistribution_Spring2021.csv
  • Contains measurements from the 2021 Delta-X Spring campaign
• DeltaX_GrainSizeDistribution_Fall2021.csv
  • Contains measurements from the 2021 Delta-X Fall campaign

Table 1. Variables in the data file. Missing data are indicated by -9999.

Variable	Units	Description
basin		Atchafalaya or Terrebonne
campaign		Spring_2021 or Fall_2021
site_id		Location name within the basin
latitude	decimal degrees	Latitude of site
longitude	decimal degrees	Longitude of site
date_time	YYYY-MM-DD HH:MM:SS	Date and time of sampling in UTC
water_velocity	m s-1	Water flow velocity- flow velocity profiles through the water column were measured while sampling suspended sediment using the ADCP
water_temp	degree C	Temperature of water samples made with a handheld pH-conductivity meter or ADCP
water_salinity	ppt	Salinity of water samples made with a handheld pH-conductivity meter. If the water temperature reading was reported from the ADCP, salinity was not reported
water_depth	m	Water depth at site from sonar measurements, by ruler (for shallow water depths), or by the ADCP
height_above_bed	m	Height above bed of sampling- Elevations of samples were made with respect to depth below the water surface, which was converted into elevation with respect to height above the sediment bed with a local measurement of river depth.
total_sediment_concentration	mg L-1	Total sediment concentration or -9999 for bed samples.
sediment_concentration_grainsize_[lower grain size]_[upper grain size]	mg L-1	Sediment concentrations by range of grain sizes. There are 100 columns with size range, lower grain size to the upper grain size, listed in field name. Grain size is in microns. For bed samples, values of these columns represent distribution fractions for different grain size groups.
sd_sediment_concentration_grainsize_[lower grain size]_[upper grain size]	mg L-1	The standard deviation of sediment concentrations by range of grain sizes. There are 100 columns with size range, lower grain size to the upper grain size, listed in field name. Grain size is in microns. For bed samples, values of these columns represent standard deviation of distribution fractions for different grain size groups.

Data note: Records with a “total_sediment_concentration” populated with a missing data value (-9999) indicate bed samples. The sediment concentration for bed samples are reported as distribution fractions for each grain size group, or a histogram with dimensionless units, in columns 13 to 112. These 100 fraction values sum to 1.0. Columns 113 to 212 list the standard deviation of these measurements by grain size.

This dataset characterizes sediment concentration with high vertical resolution in the water column and partitions concentrations according to grain size at many sites across the Wax Lake Delta. These detailed field data are required to successfully characterize and model sediment fluxes because settling and accretion of mineral sediment are highly dependent on the vertical profile and grain size of the sediment. These measurements are compared to numerical models to calibrate and validate its parameters. The hydrology models quantify the mesoscale (i.e., on the order of 1 ha) patterns of soil accretion that control land loss and gain and predict the resilience of deltaic floodplains under projected relative sea-level rise. Understanding and mitigating the impact of the relative sea-level rise on coastal deltas is urgent. If ignored, relative sea-level rise will very soon have devastating consequences on the livelihood of the half-billion people that live in these low-lying coastal regions.

Repeated grain size distribution measurements of samples were run on the Malvern Mastersizer 3000E seven times to characterize the uncertainty of grain size distribution measurements. The standard deviation is reported across the replicate measurements. Precision of instruments is listed in the next section.

Suspended and bed sediment samples were collected from a boat using a Van Dorn sampler (for suspended sediment samples) or a Ponar bed sampler (for bed samples). For suspended sediment samples, either a 2-L and 8-L Van Dorn sampler was used depending on the sediment concentration. Larger volumes are needed to collect the necessary sediment under lower sediment concentration. Sediment grain size measurements require ~0.1 g of sediment, but this amount is grain-size dependent.

The suspended sediment samples were collected at different heights in the water column. Elevations of samples were made with respect to depth below the water surface, which were converted into elevation with respect to height above the sediment bed with a local measurement of river depth. The river depth measurements were estimated through sonar measurements, ruler (for shallow water depths), or an acoustic Doppler current profiler (Teledyne RiverPro ADCP). The ADCP was used to measure flow velocity profiles through the water column while sampling suspended sediment.

The suspended sediment samples were collected from a boat drifting at approximately the same velocity as the water flow. In a rapidly moving current, this was achieved by 1) marking the profile location with a GPS point, 2) motoring the boat well upstream of the profile location along the path of a flow line, 3) putting the boat into neutral allowing it to drift over the profile location, 4) before reaching the profile location, the sampler is lowered to the desired depth as indicated by a pressure transducer mounted to the sampler, or by metering out rope, 5) the sampler doors are triggered to close at the profile location, 6) the sampler is retrieved to the boat and the boat motors back upstream to start the next drift. One sample was collected per drift.

The bed samples were collected in a similar fashion. With the boat in full drift, the sampler was positioned ~ 1 meter off the bed. Once the boat drifted over the profile location, the bed sampler was released. Upon impacting the bed, it was spring loaded to snap shut. The user then hauled the sampler to the boat with a rope. Once the sample was on board, the sample was transferred from the water or bed sampler into a plastic sample bag through a funnel. A squeeze bottle was used with river water to wash residual sediment into the bag from the funnel and the sampler. The bags were then labeled and stored them in coolers. Those handling samples wore nitrile gloves to avoid sample contamination.

Additionally, the samples in the field were filtered through polyethersulfone (PES) filter paper with pore size of 0.2 μm to recover sediment (Fig. 2). In the laboratory, the samples were prepared and analyzed for sediment concentration and grain size distribution. First, sediment from filter paper was recovered using deionized water and sonication. Then, the samples were dried under low heat (50-70°C) and weighed to calculate the total sediment concentration. The samples were then split for different analyses using the quarter-cone method. The sample splits were decarbonated using 1 M HCl for grain size analysis to remove inorganic carbon. Then, organic matter was removed by oxidation with 30% hydrogen peroxide solution and heat (~80°C). FInally, the samples were treated with sodium hexametaphosphate solution and sonicated to prevent flocculation. The grain size distribution for each sample was measured using a Malvern Mastersizer 3000E laser diffraction particle size analyzer.

Water temperature and salinity of surface water were measured in the field with a handheld pH-conductivity meter (Extech ExStik II pH/conductivity meter), which has an accuracy of ±1 °C for temperature and ±2 ppm for salinity. The surface water was sampled using a clean plastic bottle and the water temperature and salinity were measured immediately after sampling using the handheld meter in the bottle. The meter was rinsed between each use. For samples without a handheld meter measurement, the water temperature reading was reported from the ADCP and did not report salinity.

Figure 2: Example of sample filtering in the field.

None provided.