Some information on food safety from the West Virginia University extension office:
Can I eat produce from my garden after a flood? Simply put, the safest answer is no. Discarding all produce that was touched by flood water eliminates any and all risks, and is the only way to ensure you and your family do not become ill from consuming these items. Flood water can be contaminated with a variety of things including sewage, farm run-off, industrial run-off and other pollutants, and you simply don’t know what was in the water.
Read the full article here.