The Gretna 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.
Partly cloudy
Partly cloudy; warmer
Chance of showers
Mostly sunny
Mostly sunny
Partly cloudy
Mostly sunny
5.15 inches of rain fell in two days, the most for this week of the year since records began in 1956. The next wettest, 2.97 inches, fell in 1993.
Gretna’s center stands barely above sea level. Within three miles the land runs from -10 ft to 30 ft, a difference of 40 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 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.
Clay. Age: Holocene, less than 12,000 years old. About 10 mi of the line.
Silt, clay. Age: Holocene, less than 12,000 years old. About 9 mi of the line.
Clay. Age: Holocene, less than 12,000 years old. About 1 mi of the line.
Clay. Age: Holocene, less than 12,000 years old. About 0.8 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.
Gretna has a humid subtropical climate. Summer afternoons average 90° in July; winter nights fall to about 43° in January. About 64 inches of rain fall in a normal year.
On November 14 Gretna normally reaches 71° and falls to 49°. The record high is 82°, in 1993; the record low 33°, in 1969. The most rain on this date, 0.89 in, fell in 1976.
Normals 1991–2020 and records since 1956 at New Orleans Alvin Callender Field, 7 miles south-southeast. NOAA, through RCC-ACIS.
