The Coosawhatchie plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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4.92 inches of rain fell in two days, the most for this week of the year since records began in 1899. The next wettest, 2.53 inches, fell in 2019.
Coosawhatchie’s center stands about 30 ft above sea level. Within three miles the land runs from 0 ft to 110 ft, a difference of 110 ft: gently rolling country.
Under the town center the state geologic map shows Alluvial Valley Swamp (sand, gravel), from the Quaternary, less than 2.6 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sand, limestone. Age: Tertiary, 2.6 to 66 million years old. About 10 mi of the line.
Sand, gravel. Age: Quaternary, less than 2.6 million years old. About 8 mi of the line.
Unconsolidated. Age: Pleistocene, less than 2.6 million years old. About 4 mi of the line.
Sand, clay. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Coosawhatchie reaches the Atlantic Ocean by way of the Coosawhatchie and the Broad: about 25 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Coosawhatchie; river miles along the main stem, rounded.
Coosawhatchie has a humid subtropical climate. Summer afternoons average 90° in July; winter nights fall to about 36° in January. About 54 inches of rain fall in a normal year.
On November 14 Coosawhatchie normally reaches 68° and falls to 44°. The record high is 84°, in 1993; the record low 21°, in 1977. The most rain on this date, 1.09 in, fell in 1972.
Normals 1991–2020 and records since 1899 at Yemassee 1 N, 9 miles north-northeast. NOAA, through RCC-ACIS.
