The Donaldsonville 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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12.31 inches of rain fell in two days, the most for this week of the year since records began in 1893. The next wettest, 5.12 inches, fell in 1947.
Donaldsonville’s center stands about 20 ft above sea level. Within three miles the land runs from 0 ft to 60 ft, a difference of 60 ft: nearly flat ground. Open water lies within three miles.
Under the town center the state geologic map shows Natural Levees (silt, clay), from the Holocene, less than 12,000 years old.
The section below crosses 3 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.
Silt, clay. Age: Holocene, less than 12,000 years old. About 15 mi of the line.
Clay. Age: Holocene, less than 12,000 years old. About 7 mi of the line.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 2 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 Donaldsonville reaches the Gulf of America by way of the Bayou Grand Coteau: about 120 river miles.
75 miles of the trip are on the Bayou Grand Coteau.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Donaldsonville; river miles along the main stem, rounded.
Donaldsonville has a humid subtropical climate. Summer afternoons average 91° in July; winter nights fall to about 42° in January. About 63 inches of rain fall in a normal year.
On November 14 Donaldsonville normally reaches 71° and falls to 49°. The record high is 87°, in 1955; the record low 25°, in 2019. The most rain on this date, 12.1 in, fell in 1961.
Normals 1991–2020 and records since 1893 at Donaldsonville 4 SW, 3 miles southwest. NOAA, through RCC-ACIS.
