The Soviets blew a dam on this exact river in 1941 to delay the Nazi's, and killed tens of thousands of Ukrainians in the process.So, real question here, are there historical examples of attackers blowing up a dam upstream of a flood zone covering a large geographical area in which they are about to be, or currently, conducting offensive operations?
I'm fairly confident there are historical examples of defenders doing this when the attacker is in that position.
Russia has sabotaged Ukrainian dams before
To slow the German army in 1941, Russian forces blew up a major Ukrainian dam on the Dneiper River. They might have done it again this week.
taskandpurpose.com
Pretty much every dam blow I know of in history has been a defensive move, not something carried out by attacking forces, and Ukraine was not in danger of the Russians pushing across that river again, but Russia very much was in danger of Ukraine getting easy access across with the western bridging gear that has gone to Ukraine.