I have lost 50-60 acres of corn to flooding. I applied 2 quarts of atrazine...
First I hope that water is receding.
The standard recommendation in this situation is to do a bioassay where you take some of the soil from the field, place in a pot and plant bean seed to check the bean growth. If they grow then the amount of atrazine residue is not enough to interfere with bean growth and you should be successful. As the water recedes you can take the soil sample and dry it out quicker than the whole field, so you would have you answer before the field is ready to plant.
On a practical level others have done this before and not had problems planting beans. Unfortunately every situation is not the same so a blanket recommendation can be made.