Geophysical Data Collected in the Cedar River Floodplain, Cedar Rapids, Iowa, 2015-2017

A suite of geophysical methods was used along the Cedar River in Cedar Rapids, Iowa to support the hydrogeologic characterization of the alluvial aquifer associated with the river and to assess the area for suitability for larger-scale airborne geophysics. The aquifer is comprised of sand and gravel, interbedded with finer sediments, and underlain by carbonate-dominated bedrock. The aquifer is the principal source of municipal drinking water for the City of Cedar Rapids. The raw data provided here includes waterborne continuous resistivity profiling (CRP) and continuous seismic profiling (CSP) data (collected at the same time), electrical resistivity tomography (ERT) profiles, and horizontal-to-vertical spectral ratio (HVSR) seismic from April 2015. Also, several borehole geophysical logs including nuclear magnetic resonance (NMR), gamma, and electromagnetic induction (EMI) from nine wells, collected in June 2017, are provided. The CRP, ERT, and borehole logs measure the electrical properties of the subsurface, which can be related to stratigraphic layers. The CRP, CSP, HVSR, and some of the borehole logs characterize the depth to bedrock. Collectively, the suite of methods can help characterize the subsurface and map the extent of the sand and gravel aquifer. In addition, these geophysical measurements can be used to plan and to ground-truth air-borne electromagnetic surveys.