Surface runoff (also known as
overland flow) is the flow of
water that occurs when excess
stormwater,
meltwater, or other sources flows over the earth's surface. This might occur because
soil is saturated to full capacity, because rain arrives more quickly than soil can absorb it, or because areas (
roofs and
pavement) send their runoff to surrounding soil that cannot absorb all of it. Surface runoff is a major component of the
water cycle. It is the primary agent in soil erosion by water.