Delta-X: Acoustic Doppler Current Profiler Channel Surveys, Coastal Louisiana, 2021

This dataset provides river discharge measurements collected at selected locations in the Atchafalaya and Terrebonne Basins within the Mississippi River Delta floodplain in coastal Louisiana, USA. The measurements were made during the Delta-X Spring campaign from 2021-03-26 to 2021-04-11. Channel surveys were conducted with a Teledyne RiverPro acoustic doppler current profiler (ADCP) on selected wide channels (>100 m wide) and a few selected narrow channels (approximately 10 m wide).

This dataset includes 348 files in comma-separated values (*.csv) format. Also included are three companion files: one each in image (*.jpg), compressed Keyhole Markup Language (*.kmz), and Portable Document (*.pdf) formats.

This dataset provides river discharge measurements collected at selected locations across the Atchafalaya and Terrebonne Basins in Southern Louisiana, USA, within the Mississippi River Delta (MRD) floodplain. The measurements were made during the Delta-X Spring campaign from 2021-03-26 to 2021-04-11. Channel surveys were conducted with a Teledyne RiverPro acoustic doppler current profiler (ADCP) on selected wide channels (>100 m wide) and a few selected narrow channels (approximately 10 m wide).

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 Datasets

Christensen, A.I., T.M. Pavelsky, D.J. Jensen, and K. Liu. 2020. Pre-Delta-X: River Discharge Channel Surveys across Atchafalaya Basin, LA, USA, 2016. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1806

• The preliminary dataset that lead to the formation of the current dataset.

Denbina, M.W., M. Simard, T.M. Pavelsky, A.I. Christensen, K. Liu, and C. Lyon. 2020. Pre-Delta-X: Channel Bathymetry of the Atchafalaya Basin, LA, USA, 2016. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1807

Denbina, M.W., M. Simard, E. Rodriguez, X. Wu, and C. Michailovsky. 2021. Pre-Delta-X: L3 AirSWOT-derived Water Level Profiles, Wax Lake Outlet, LA, USA, 2015. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1819

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: 1 m

Temporal Coverage: 2021-03-26 to 2021-04-11

Temporal Resolution: One-time estimates

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

Site	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude
Atchafalaya and Terrebonne Basins	-91.45	-90.82	29.70	29.16

Data File Information

This dataset includes 348 files in comma-separated values (*.csv) format. Also included are three companion files: one each in image (*.jpg), compressed Keyhole Markup Language (*.kmz), and Portable Document (*.pdf) formats. Most files are named ADCP_YYYYMMDD_hh:mm:ss_AAA_BBB_CCC_RepD_Bathy.csv, where:

YYYYMMDD = date as year, month (MM), and day (DD),
hh:mm:ss = time of arrival to site in hour (hh), minute (mm), and second (ss) of local, Central Daylight Time (UTC -5 h),
AAA = location name,
BBB = site name,
CCC = transect number, and
D = replicate number.

Table 1. File names and descriptions.

File Name	Description
Data Files
ADCP_YYYYMMDD_hh:mm:ss_AAA_BBB_CCC_RepD_Bathy.csv	Data from individual transects, including bathymetry and discharge measurements. These file should be considered raw data. Some files are missing longitude-latitude coordinates; however, transect coordinates are available from DeltaX_RiverDischarge_Spring2021.csv in the planned_latitude and planned_longitude fields.
DeltaX_RiverDischarge_Spring2021.csv	Summary information for each channel transect and includes longitude-latitude coordinates for each transect.
Companion Files
DeltaX_ADCP_locations_spring2021.jpg	Provides the site locations (small red diamonds) overlaid on a satellite image.
DeltaX_ADCP_locations_spring2021.kmz	Provides locations viewable in Google Earth.
DeltaX_ADCP_Measurements.pdf	A PDF version of this user guide.

Data File Details

The files contain location coordinates in longitude, latitude (EPSG: 4326). Missing data are indicated by the value -9999.

Table 1. Variables in the summary file DeltaX_RiverDischarge_Spring2021.csv.

Variable	Units	Description	Collected During Pre-Delta-X Campaign?
basin	text	Name of estuary basin: “Atchafalaya” or “Terrebonne”	Yes
campaign	text	Campaign name (e.g., Spring 2016)	Yes
transect	1	Order number of transect at a site	Yes
location	text	General location of transect (e.g. ATCH, ICWW, FLB)	No
site_name	text	Name of site	No
replicate	1	The replicate number for given transect	No
planned_latitude	degree_north	Planned location of transect	Yes
planned_longitude	degree_east	Planned location of transect	Yes
start_date	YYYYMMDD	Start date of the transect in year (YYYY), month (MM), and day (DD)	Yes
start_time	hh:mm:ss	Start time of the transect in hour (hh), minute (mm), second (ss) UTC	Yes
start_ensemble	1	The first ensemble included in the transect	No
start_latitude	degree_north	Location of transect start. ‘-9999’ values indicate no valid GPS data available	Yes
start_longitude	degree_east	Location of transect start. ‘-9999’ values indicate no valid GPS data available	Yes
end_date	YYYYMMDD	End date of the transect in year (YYYY), month (MM), day (DD)	No
end_time	hh:mm:ss	End time of the transect in UTC	No
end_ensemble	1	The last ensemble included in the transect	No
end_latitude	degree_north	Location of transect end. ‘-9999’ values indicate no valid GPS data available	No
end_longitude	degree_east	Location of transect end. ‘-9999’ values indicate no valid GPS data available	No
width	m	Width of the channel	Yes
area	m2	Area of the channel	Yes
boat_speed	m s-1	Average boat speed during the transect	Yes
mean_speed	m s-1	Average water speed during the transect	Yes
discharge_side	m3 s-1	Sum of discharge on the left and right edges of the transect	Yes
discharge_top	m3 s-1	Discharge in the top portion of the transect	Yes
discharge_middle	m3 s-1	Discharge in the middle portion of the transect	Yes
discharge_bottom	m3 s-1	Discharge in the bottom portion of the transect	Yes
discharge_total	m3 s-1	Total discharge	Yes
flow_direction	degree_from_north	Azimuth direction of water flow	No
file_name	text	Name of raw data file	Yes
profiler_id	text	Instrument used	Yes

Table 2. Variables in files named ADCP_YYYYMMDD_hh:mm:ss_AAA_BBB_CCC_RepD_Bathy.csv. User Note: This file should be considered raw data. Some files are missing longitude-latitude coordinates; however, transect coordinates are available from DeltaX_RiverDischarge_Spring2021.csv in the planned_latitude and planned_longitude fields.

Variable	Units	Description
ensemble	1	Ensemble number
date	YYYYMMDD	Date of the transect in year (YYYY), month (MM), and day (DD)
time	hh:mm:ss	Time of the ensemble in hour (hh), minute (mm), second (ss) UTC
distance_traveled	m	Distance traveled since the beginning of the transect
river_depth	m	Measured river depth
latitude	degree_north	Location of transect start. ‘-9999’ values indicate no valid GPS data available
longitude	degree_east	Location of transect start. '-9999’ values indicate no valid GPS data available

Companion files: Two files illustrate the planned sampling locations for all ADCP transects (points mark an edge of each transect):  DeltaX_ADCP_locations_spring2021.kmz provides labeled locations in Keyhole Markup Language (KML/KMZ) file compatible with Google Earth. DeltaX_ADCP_locations_spring2021.jpg shows the locations (small red circles) overlaid on a satellite image.

 

Understanding and mitigating the impact of the relative sea-level rise on coastal deltas is an urgent concern. If ignored, 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. Estuarine wetlands provide protection from storms and confer some resilience in the face of environmental change. Therefore, understanding the processes that control the location, extent, and topography of these ecosystems is essential. 

This dataset is used to calibrate and validate Delta-X’s hydrodynamic models. Acoustic doppler current profiler (ADCP) data provide near-instantaneous estimates of river discharge across the sampled channels at particular times. These locations and time-specific measurements are compared to hydrodynamic models to calibrate and validate their parameters. The hydrology models quantify the mesoscale (i.e., 1 ha) patterns of soil accretion that control land loss and gain (Simard et al., 2017), and they predict the resilience of deltaic floodplains under projected sea-level rise. 

Two or more replicate transects were taken and compared at each site. Transects were inspected for data loss due to instrument communication issues, and transects with lost data were removed. The goal was for measured discharge of replicates to differ by no more than 5%. This standard was met in most cases, except where flow rate was very small. Replicate transects are included in this dataset to allow the user to compare transects.

Acoustic doppler current profiler (ADCP) measurements of discharge rates were collected in estuarine channels of the Atchafalaya River and Terrebonne Basin in coastal Louisiana (Fig. 1) in March and April 2021. Before the campaign, 53 sites were chosen as part of a sampling design to incorporate major river channels in both basins and smaller channels surrounding Delta-X intensive study sites. Cross-sectional surveys of all wide channels (>100 m wide) and selected narrow channels (approximately 10 m wide) were conducted under AirSWOT flight paths (swaths) in the Atchafalaya River Basin. AirSWOT is an airborne instrument used to measure water levels during tidal cycles for Delta-X (Denbina et al., 2019; Denbina et al., 2021). River discharge was measured on cross-channel transects at these sites. Transects were spaced at six times the river width, making sure to target each total pressure transducer location (Simard et al., 2020). Transect site selection followed the guidelines in Mueller et al. (2013).

Measurements were made using a Teledyne RiverPro ADCP instrument. For each transect, the ADCP was mounted to a boat, collecting flow measurements while crossing each channel, perpendicular to flow (Fig. 2). The majority of transects were collected by the Coastal Studies Institute (CSI) at Louisiana State University (Fig. 2A) with the ADCP mounted to the front of the boat. An additional 16 transects were collected by the California Institute of Technology (Caltech) with the ADCP mounted to the port side of the boat (Fig. 2B). Each team collected cross-channel transect measurements at each site, returning multiple times to collect data during different stages of the tidal cycle.

Figure 2. (A) Researchers from Louisiana State University Coastal Studies Institute and (B) researchers from California Institute of Technology taking ADCP measurements along channel transects. The ADCP instrument was mounted to the front (A) or side (B) of the boat.

Teams collected two or more replicates of each transect to ensure data quality. The CSI team collected one continuous back and forth transect, which was split and processed separately using WinRiver II software (Teledyne RD Instruments, 2018). Methods for transect data collection are described in chapter 10 of the WinRiver II User Guide (Teledyne RD Instrument, 2018). At the beginning of each day in the field, calibration tasks (e.g., compass calibration, system tests, and site setting adjustments) were performed on the ADCP instrument according to instructions in the WinRiver II User Guide.

The CSI team experienced communication issues between the ADCP and the external GPS unit (Vector VS1000), which produced significant errors in the timestamp of GPS data for some transects. Post-processing was required in all CSI transects to correct external GPS data when possible or to replace external GPS data with internal GPS data from the ADCP instrument. In many cases, GPS data are not available for an ensemble and are replaced with -9999 values. Fortunately, transects were completed at planned locations, and users are encouraged to use planned coordinates (‘planned_longitude’ and ‘planned_latitude’ variables in DeltaX_RiverDischarge_Spring2021.csv) as a reference to transect location. Due to issues with external GPS data, the bottom track was used as the reference track for all CSI transects. The Caltech team used an external RTK GPS unit (Trimble R12), which was merged with the ADCP data during post-processing. Additionally, there are no moving-bed corrections due to errors in moving-bed tests while on site.

Denbina, M., M. Simard, E. Rodriguez, X. Wu, A. Chen, and T. Pavelsky. 2019. Mapping water surface elevation and slope in the Mississippi River Delta Using the AirSWOT Ka-band interferometric synthetic aperture radar. Remote Sensing 11:2739. https://doi.org/10.3390/rs11232739

Denbina, M.W., M. Simard, E. Rodriguez, X. Wu, and C. Michailovsky. 2021. Pre-Delta-X: L3 AirSWOT-derived Water Level Profiles, Wax Lake Outlet, LA, USA, 2015. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1819

Mueller, D.S., C.R. Wagner, M.S. Rehmel, K.A. Oberg, and F. Rainville. 2013. Measuring discharge with acoustic Doppler current profilers from a moving boat. Techniques and Methods, book 3, chapter A22. U.S. Geological Survey. https://dx.doi.org/10.3133/tm3A22 

Simard, M., M.W. Denbina, D.J. Jensen, and R. Lane. 2020. Pre-Delta-X: Water Levels across Wax Lake Outlet, Atchafalaya Basin, LA, USA, 2016. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1801

Simard, M., K. Liu, M.W. Denbina, D. Jensen, E. Rodriguez, T.H. Liao, A. Christensen, C.E. Jones, R. Twilley, M.P. Lamb, and N.A. Thomas. 2017. Modeling river discharge and sediment transport in the Wax Lake-Atchafalaya basin with remote sensing parametrization. AGU Fall Meeting, abstract: H52G-06. https://agu.confex.com/agu/fm17/meetingapp.cgi/Paper/236837

Simard, M., M.W. Denbina, D.J. Jensen, and R. Lane. 2020. Pre-Delta-X: Water Levels across Wax Lake Outlet, Atchafalaya Basin, LA, USA, 2016. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1801

Teledyne RD Instruments, Inc. 2018. WinRiver II Software User’s Guide. P/N 957-6231-00.