Plan for something serious, not for a picnic. If you have the space, 30-days per person should be a start and go from there. Think about Hurricane Katrina if you were at the epicenter.
Water should be stored in large containers to maximize storage capability. Keep bleach & a backpacking water filter handy. Both come in handy for treating long-standing water, or if your water source is contaminated by flooding. Use a rubber hose to transfer to drinking containers.
For longer term, think storing whole grains & other dried foods in 5-gallon sealed buckets. These can last for years. IIRC, even CostCo was selling 'preparedness kits' in 5-gallon containers.
Guns & ammo. Keep the ammo triple bagged and stored off the ground in case of water seepage.
Clothing, cook kits, sleeping supplies, toilet paper and fuel. I'd also consider a few rolls of American Eagle silver dollars, one oz. pure silver each, may come in handy for buying things like medical supplies, gasoline, ammunition if things get really bad.