Need Some In Put on new hay ground .

I guess Im the new guy on forum but have visted this site several times and read about several topics. I have become a hay producer for several farms over the last couple years and have some good ground around me but I have just got a farm next to me that has had horses on it for 10 + years and is weed invested. The current owner has got rid of horses  and has decided to do other things in life now ].  He has turned farm over to me and I am wanting to turn weeds into hay ground and make some thing out of the creek bottom field. My question is do I need to plow under and work ground or spray and seed drill it . The field lays on a creek bottom and the water table is usually good so the weeds have thrived in there since horses have destroyed the grass . The ground will sometimes flood in winter months when we have lots of rain and I wondered If fescue would be the only thing that would withstand being submerged in water for sometimes a day or two at most or would other grasses survive it . Thanks for any input , I do plan on getting soil samples in next week or so to see where I stand on ground but I thought Id ask advise on it also . My goal is to produce a good stand of hay to square bale since I have a barn right there to put it in. Will Alfalfa take the flooding in winter ? Spring and summer it stays dry unless creek rises from lots and lots of rain . Thanks for any help .............   

Need Some In Put on new hay ground .