Spatial and temporal imaging of a cover-collapse sinkhole in west-central Florida through high resolution remote sensing and geophysical techniques

On July 14, 2017, a cover-collapse sinkhole formed in the front yard of a home in Pasco County, FL. Starting as a depression, the initial collapse occurred rapidly (120 minutes) with subsequent slumping over the course of three days. The sinkhole is oval and cone-shaped with a northeast-southwest long axis and ridges on the northwest and west slopes. A combination of remote sensing, geophysics, and soil borings are used to characterize the temporospatial surface changes and subsurface structures at this sinkhole. Repeat surveys started four days post-collapse and concluded 10 months post-collapse. Surface changes over time are computed using terrestrial laser scanning (TLS) and drone-based structure-from-motion (SfM) photogrammetry, with the Multiscale Model to Model Cloud Comparison algorithm. The initial collapse area measured 1,395 square meters (day 4) and grew to a maximum of 1,626 square meters (day 32) before stabilization efforts partially the sinkhole and built up the perimeter walls. Post-collapse and pre-stabilization activity in the form of perimeter growth occurred on the northeast and southwest edges. Ground-penetrating radar detected a semicontinuous horizon within sands and silts that appears to correspond to the historic ground surface present before portions of the nearby Saxon Lake were filled in as part of agricultural and housing development modifications to the area in the 1960s and 70s. The direction of the collapse’s long axis, post-collapse activity, and the orientation and depth of a semicontinuous subsurface horizon all suggest a northeast-southwest trending linear or elongated karst feature contributed to the collapse and subsidence.