Airborne electromagnetic, magnetic, and radiometric surveys of the Mississippi Alluvial Plain and Chicot Aquifer System, March 2018 and May - August 2021

Airborne geophysical surveys were acquired in March 2018 and May 25 through August 7, 2021 using a helicopter-based platform. These surveys were collected along 10,706 line-kilometers (line-km) within selected areas of the Mississippi Alluvial Plain (MAP) and the Chicot Aquifer System in the southeastern United States. The airborne geophysical surveys include electromagnetic, magnetic, and radiometric sensor data collected in rivers and levees throughout the two areas to evaluate groundwater and surface-water interaction, riverine ecosystems, and infrastructure.

This data release contains three child items that provide:

Minimally processed (raw) data supplied by the airborne contractor (Xcalibur Multiphysics) for all three sensors along all flight lines: Airborne electromagnetic, magnetic, and radiometric surveys of the Mississippi Alluvial Plain and Chicot Aquifer System, March 2018 and May - August 2021: Raw Data
Fully processed electromagnetic data: Airborne electromagnetic, magnetic, and radiometric surveys of the Mississippi Alluvial Plain and Chicot Aquifer System, March 2018 and May - August 2021: Processed Data
Final inverted resistivity models: Airborne electromagnetic, magnetic, and radiometric surveys of the Mississippi Alluvial Plain and Chicot Aquifer System, March 2018 and May - August 2021: Resistivity Models

Supporting documentation contained in this data release include:

Contractor's report- Description of data acquisition and minimal processing as conducted by Xcalibur Multiphysics (Airborne Survey Contractor).

Organization:
The data files contained in this release are broken up according to the three main objectives of these surveys:  1) River surveys along the thalweg of major rivers within the MAP and the Chicot Aquifer extents; 2) Levee surveys along the Mississippi and Arkansas rivers from Cairo, IL to Baton Rouge, LA and northwest from the confluence of the Mississippi and Arkansas rivers to Pine Bluff, AR; and 3) Gridded products focused on gravel bars within the Mississippi River from Helena, MS to the confluence with the Arkansas River.

Data were collected on the following 16 rivers:

Rivers within the MAP boundary:  Black, White, Big Sunflower, Little Sunflower, Ouachita, Tensas, Obion, Saline, Little Red, and Bogue Phalia.
Rivers within the Chicot Aquifer extent:  Mermentau, Calcasieu, Sabine, Vermillion, Bayou Teche, and Bayou Lacassine.

Levee Surveys:
Along selected reaches of the Mississippi and Arkansas Rivers, levee survey lines were flown along the toe of the levee both on the side adjacent to the river and on the side opposite the river.  In addition, where possible, a third line was flown 91m (300 feet) offset from the toe of the levee opposite to the river. Additional processing was done on all levee lines and is described in the data dictionaries and processing step sections of the metadata included in the “Processed Data” and “Resistivity Models” child items of this data release.

Seven gridded surveys were also collected:

Mississippi River gravel bars: 

250 m Line Spacing

 Prairie Point
 Island 63
 Crumrod

100 m Line Spacing

White River

  Melton Grid:23 line-km at a 100 m line spacing over a site near Minter City, MS.
  AR OSL Grid: 268 line-km at a 500 m spacing over a series of the drill core locations near Paragould, AR.
  Raccourci Grid:100 line-km at variable spacings over Raccourci Old River, a relic oxbow near Batchelor, LA.

Additional Data:
A dataset collected on levees near Greenville, Mississippi, in March 2018 is also included in this data release.  The survey includes four lines parallel to and over the levee for a total of 27 line-km. This dataset was collected as an evaluation of the technical approach used on the more comprehensive surveys in the MAP and Chicot Aquifer extents. This dataset contains AEM data only (magnetic and radiometric data were not collected).

Additional details on flight line numbers and citations for the various methods used in the collection and processing of the radiometric data are included in the supplemental section.