Strong winds and storm surge from Hurricane Isaac's
landfall forced the Mississippi River to flow backward for nearly 24
hours on Tuesday, the U.S. Geological Survey said Thursday.
The USGS stream gage at Belle Chasse, Louisiana, showed the
Mississippi flowing upstream at 182,000 cubic feet per second, surging
to 10 feet above its previous height. Average flow for the Mississippi
River at Belle Chase is about 125,000 cfs, toward the Gulf of Mexico,
the USGS said.
"Although it doesn't happen often, hurricanes can cause coastal
rivers to reverse flow," a release from the agency said. "Between the
extremely strong winds and the massive waves of water pushed by those
winds, rivers at regular or low flow are forced backwards until either
the normal river flow or the elevation of the land stop the inflow."
Storm surge from Isaac has been observed as far north as Baton Rouge, USGS said.
"This reversal of flow of the mighty Mississippi is but one measure
of the extreme force of Isaac," said USGS Director Marcia McNutt. "While
such events are ephemeral, they are yet another reminder of why we need
to respect hurricane warnings."