[Quix]

A sufficiently large or sufficiently long lasting tsunami tidal bore type wave on top of the usual Mississippi water would have looked to folks of that era in that location as though the river was ‘running backwards,’

imho.

[Figment]

A sufficiently large or sufficiently long lasting tsunami tidal bore type wave on top of the usual Mississippi water would have looked to folks of that era in that location as though the river was running backwards imho.

Even if it only stopped flowing south in a stretch of the lower Mississippi, it would be catastrophic today. Many take flowing backwards too literally. It was definitely disturbed and distracted from its normal flow