Continuous Resistivity Profiling (CRP) in the Des Moines River and Beaver Creek, Des Moines, Iowa, 2018

In September 2018, approximately 13 miles of continuous resistivity profiling (CRP) surveys were collected on the Des Moines River and Beaver Creek in Des Moines, Iowa. The CRP method was used to characterize the resistivity of the water column and the underlying geologic materials. Three CRP line profiles were collected during one day of field work and were collected concurrently with continuous seismic profiling (CSP) methods. For this investigation, 11 electrodes spaced 10 m apart and mounted in a streamer were towed behind a manned boat and data were collected using the dipole-dipole array type. The first two electrodes, closest to the boat were used to inject current into the water and river bottom, and eight electrical potential measurements were made using the remaining nine electrodes. With this system, a complete suite of measurements is collected every 2.8 seconds. Considering the boats slow rate of speed a complete measurement is taken about every 3-5 meters of boat movement. In general, voltage measurements taken with larger electrode spacings extend deeper into the subsurface. The exact depth and resistivity are determined through a process of inversion. Data were collected concurrently with CSP methods. Both methods used the same .gps files for georeferencing. Starting and ending coordinates for each line are specified in readme_CRP. This data release contains a notes file for archiving surface-geophysical data (CRP_Archive_Notes_DesMoinesIA.csv), a text file (Readme_CRP.txt) explaining the data files and processing references, and a color scale file (CRP_colorscale.png) relating colors to resistivity values. This data release also contains compressed zip folders (one for each survey line) that contain the original instrument files (windows command script, .crs, .stg, and .gps), two .xyz files (raw data culled and inverted data), and the inverted model output image for each survey line (.wmf). Field notes taken at the time of data collection are not included in this data release but are available upon request.