Sinkhole flooding above a shallow bedrock aquitard in an urbanizing community, central Tennessee, USA

In the aftermath of a storm on 6 February 2020, central Tennessee, USA flooded sinkholes were concentrated in places where two Late Ordovician aquitards are probably at or within similar to 10 m of the surface. The similar to 278 km(2) study area is located similar to 35 km SE of central Nashville along the edge of Murfreesboro, a city of >153,000 that grew in population by similar to 40 % between 2010 and 2020. Within the study area, the largest amount of flooding happened within the similar to 12 km(2) Shores Road focus area which includes the city boundary and is mostly within the city's urban growth boundary. Analysis of published geologic maps and stratigraphic observations reveals areas where bedrock aquitards are probably at or within similar to 10 m of the surface, and inundation was observed on 3 m cell size Dove multispectral satellite imagery on 8 February. The largest inundated areas were mapped with similar to 88 % accuracy through supervised classification of the 8 February scene. Of 1247 inundated features in the study area, 233 (similar to 19 %) are in areas where the Pierce Limestone aquitard is at or within similar to 10 m of the surface, and this result is statistically significant at the p < 0.01 level because these areas comprise only 8 % of the study area. These 233 features account for similar to 27 % of the inundated area. If areas underlain by a second aquitard, the Lower Ridley Confining Layer, are included in the analysis, this approach explains similar to 69 % of the features and similar to 86 % of the inundated area. This result is also significant at the p < 0.01 level. Although many factors affect sinkhole formation and flooding in general, these results underscore the significance of shallow bedrock aquitards.

Automated summary

In the aftermath of a storm on February 6, 2020, central Tennessee, USA experienced flooding and sinkholes, primarily concentrated in areas where two Late Ordovician aquitards are close to or within 10 meters of the surface. The study area of approximately 278 square kilometers is located about 35 kilometers southeast of central Nashville. Analysis reveals that bedrock aquitards near or within 10 meters of the surface significantly contribute to flooding and sinkhole formation. This highlights the importance of shallow bedrock aquitards in understanding and predicting these phenomena.