If your home has a basement, you may have to clean a flooded basement at least once. Shut down the electrical power, gas, and water to the basement before entering the area. Check for broken pipes or fittings after the water goes down. Call an experienced plumber who knows what do if you are not comfortable handling the problem.
When it is flooded outside, the water inside is bracing the walls against the outside pressure of waterlogged soil and high waters. Do not drain the water in the basement until the outside water has gone down. It will prevent heaving of floors and pushed in walls.
Get the water out of the basement when it is safe. If there isn’t a drain or the water is extremely high, rent a sump pump. If your electrical panel is damaged, ask the rental company if they have a 12-volt car battery pump or gasoline operated pump.
If there is a drain and it isn’t working, clear the debris away from the opening and remove the drain plate. Use some old kitchen tongs to remove the debris inside the pipe. You might have to rent an auger to clear blockages close to the drain. Once the water is drained, open the doors and windows to allow the moisture to go outside.
Use a flat-bladed shovel to scoop up mud and debris. Place the gunk in 5-gallon buckets to be carried upstairs and disposed of in accordance with local health regulations. There are contaminants and germs, and the less opportunity for them to spread, the better for everyone concerned. Wear a mask, goggles, gloves, and waterproof boots while you are working.
Use a high-power pressure hose to get rid of dirt and silt stains on masonry and concrete walls and foundations. Tackle stubborn stains by scrubbing with a stiff bristle brush and household detergent. Rinse the areas off with clean water as you clean from top to bottom.
Fans and dehumidifiers help dry things out. You want to prevent mold, so tear up the carpet and padding and dispose of it. Get the subflooring dry.
Sometimes the odors hang around. Put a lump of dry charcoal into an open metal or tin container and place it on a shelf or the floor of the basement. The charcoal absorbs the odors. Drywall soaks up water like a sponge. Take it off and replace it after the wood framing is dry.