Electric Resistivity Tomography (ERT) surveys conducted near campgrounds on the Buffalo National River, Arkansas

Karst environments present many challenges to agencies and engineers attempting to work in these landscapes, particularly towards building infrastructure. The interconnectivity of karst hydrologic systems means that activities occurring on the surface of a karst landscape can have an impact on water quality and quantity. Additionally, soil thickness in karst landscape is often highly variable due to the presence of solutionally-enlarged fractures, joints, and openings at the soil-bedrock interface. Therefore, when planning infrastructure in karst terrains it is critical to do a thorough assessment to ensure that planned activities will not negatively impact the sensitive environment. In October 2020 Electric Resistivity Tomography (ERT) surveys were conducted at two National Park Service (NPS) campgrounds on the Buffalo National River: Kyles Landing and Ozark campgrounds. The surveys were done in order to map the thickness of soil over the bedrock surface to aid NPS management in making future decisions regarding the wastewater treatment systems for both campgrounds. This data release includes three types of data: (1) raw direct current (DC) resistivity data, (2) inverted resistivity data, and (3) geospatial data collected via global positioning system (GPS) of the electrode locations and other relevant geospatial data. A data dictionary is included along with the data and defines all of the table headings, definitions, and units. Additional information related to the collection of the data present are included in the process steps within the metadata. An Iris Syscal Pro Switch 96 resistivity meter (http://www.iris-instruments.com/syscal-prosw.html) was used to conduct the DC resistivity survey along with a series of cables to connect a total of 96 electrodes. Resistivity arrays were designed using the Electre 2.03 software by Iris Instruments (http://www.iris-instruments.com/download.html#processing). Electrodes were connected to steel pins driven into the soil at set spacings. In most cases 2D resistivity arrays were used for data collection, however; at Ozark campground one 3D resistivity array was collected as a proof of concept. The geographic location and elevation for each electrode was also surveyed using a differential GPS. A Hemisphere SmartLink Antenna with Atlas H10 differential correction was used to georeference each stainless-steel pin location as well as other relevant features including river levels, benchmarks, and features related to nearby infrastructure. In all cases, once the GPS had acquired satellite connectivity the device was left to acquire position until horizontal (2D) position was less than 10 centimeters (cm), and vertical (3D) position was less than 15 cm. These locations were then used in the inversion process required to interpret the geophysical data.