From Longman Dictionary of Contemporary Englishfloodwaterflood‧wa‧ter /ˈflʌdwɔːtə $ -wɒːtər, -wɑː-/ noun [plural, uncountable] water that covers an area during a flood
Examples from the Corpus
floodwater• 2500 residents were forced out of their homes by floodwaters.• At Challow in Oxfordshire, deep floodwater meant it was strictly snails pace only for motorist.• Each wave brought more floodwater through those broken windows, negating the work of sump-pumps.• Elsewhere, vehicles were stranded in the middle of lakes of floodwater.• The rate of rise of floodwater in normally dry watercourses is, in many cases, extreme.• Looking out to the west, I thought I could see floodwater, but it was smoke.• No one in town has taken floodwater, though some basements are wet from seepage.• The floodwater, carrying branches and driftwood, was over the roadway on the curved iron bridge.• Mekinock was evacuated when floodwater washed through town. 