Come to think of it, I could do that in LTTW, as that involved similarly re-flooding the Fens because of the invasion and I never specified whether they put it right afterwards...ooooo
I did make a start on a story set in an alternate world where we lost WW1, and it featured an attempted German landing on the East Coast, which led to us reflooding the Fens in a panic. Post-war Britain loses a lot of colonies and has to pay big reparations to Germany (who desperately needs that cash, much more than we did OTL) so we can't afford to put it right.