Stormwater runoff is water from precipitation that does not soak into the ground. Such as rooftops, over paved areas, bare soil, and through sloped lawns. Stormwater runoff then accumulates in and flows through natural or man-made conveyance systems during and immediately after a storm event. Natural conveyance systems are rivers, streams, brooks, wetlands, etc. Man-made conveyance systems are bridges, culverts, pipes, catch basins, etc.