Whether grass is damaged by flooding depends on several factors:

• Turf species (bermudagrass and creeping bentgrass, Kentucky bluegrass, perennial ryegrass and annual bluegrass)
• Amount of time the turf is submerged
• Depth of water
• Light intensity
• Temperature of the water

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