[Strategerist]

Wasn't extensive flooding thought to have played a role, in the last big quake along the New Madrid?

No. The quake series was during the middle of the winter.

[RegulatorCountry]

"Upon the whole, this has been an uncommon year; the early melting of snow to the north raised the Mississippi to an unusual height. The continued rains in the summer and the subsequent hot weather, and consequent sickness amongst the inhabitants, rendered that period somewhat distressing. Autumn, to this time, has been unusually mild..."

LOUISIANA GAZETTE (ST. LOUIS) -- Vol IV

Link:
http://www.eas.slu.edu/Earthquake_Center/SEISMICITY/Nuttli.1973/nuttli-73-app.html