Apres moi, le déluge.....
I had never heard the "ice break-up" derivation before.
debacle - "disaster," 1848, from Fr. débâcle "breaking up of
ice on a river," figuratively extended to the violent flood that
follows when the river ice melts in spring, from débâcler "to
free," from M.Fr. desbacler "to unbar," from des- "off" +
bacler "to bar," from V.L. *bacculare, from L. baculum
"stick." Sense of "disaster" was present in Fr. before Eng.
borrowed the word.