Whether grass is damaged by flooding depends on several factors:
In one experiment, creeping bentgrass survived 60 days of flooding at a water temperature of 50°F but less than 10 days at a water temperature of 86°F (Beard 1973). The good news is that many turf species have the ability to survive adverse conditions, including flooding. The following articles provide further information and details about turfgrass flooding and recommendations for recovery:
Will my turf recover from recent flooding? - Michigan State
It's Raining, It's Pouring, The Golf Course is Flooding - USGA