Much of the Beidler Forest is a swamp – a flooded forest where the water level fluctuates rather dramatically, some areas may occasionally be completely dry. The water doesn’t come from streams or springs but from rainfall draining from the four hundred and thirty thousand acres watershed above Four Holes Swamp, of which Beidler is a part. Think of a swamp as a massive porous surface – rainwater can slowly infiltrate the soil and pollutants – fertilizers, motor oil from roadways, industrial waste, sewage -- are broken down by soil organisms into non-toxic substances. The water level fluctuates with rainfall but inexorably slowly flows across the land, from wetter to drier sites before ending in the Edisto River. After excess rainfall events, that slow passage mitigates flooding of that River and adds cleansed water for the backup supply of Charleston’s drinking water.