After a disastrous storm, water below ground level must be removed slowly to equalize pressure on both sides of the basement walls, says David Miller, an administrator with the Iowa Homeland Security and Emergency Management Division. Pumping it out too quickly or too early can cause structural damage or a cave-in. "The water in your basement is pushing back, preventing your basement walls from collapsing," says Miller.
Test groundwater levels by digging down a few inches just outside your basement. If the water pools, wait a day or two to hook up a submersible pump. Don't go in without turning off the electricity first (if you can't, call your utility and don't go in at all). Don gloves, eyewear, and a mask to protect yourself from cleaning agents or wastewater that may have seeped into the basement soup. On the first day, remove just one foot of water (send it as far from the house as possible, preferably to a storm drain) and wait overnight. If the water level is back up, it's too early to pump. Once the water stops rising, pump out two or three feet each day until the basement returns to dry land.
Get all the know-how at Drying Out a Wet Basement