First, treat active flooding carefully
If water is near electrical equipment, outlets, panels, appliances, or unknown hazards, avoid entering the water until the area is made safe. Severe flooding may require emergency water-removal or utility assistance before waterproofing work begins.
After the water is controlled
Look for the pattern: storm-related seepage, sump failure, wall or floor entry, plumbing leakage, or exterior drainage. The waterproofing solution depends on the source.
Preventing repeat basement water
Long-term measures may include sump pump work, drainage, crack repair, or broader basement waterproofing.