Disaster 1990! was a prequel to the series Invasion! which ran in 2000 AD progs 119-139 in 1979. Written by Gerry Finley-Day and drawn mostly by Carlos Pino, it saw battling truck driver Bill Savage and his ally Professor Steve Bamber fighting for survival in a Britain partly flooded when a nuclear accident caused melting of the North polar ice cap, along the way taking on such opponents as the fascistic Legion of London and the crazed Doctor Pyke until the flood waters eventually froze over and allowed the reclamation of the country to begin. Its canonicity as regards Savage's other adventures in 2000 AD is uncertain as these events are never mentioned in the other strips he appears in.
The series is reprinted in Disaster 1990! Vol 1, given away free with the Judge Dredd Megazine in 2013.