Definitions for "Surface runoff"
Precipitation, snow melt, or irrigation in excess of what can infiltrate the soil surface and be stored in small surface depressions; runoff is a major transporter of non­point source pollutants.
That portion of rainfall that is not immediately absorbed into the soil and becomes overland flow
Precipitation that exceeds the infiltration capacity of soils and reaches streams relatively fast, via the land surface. This produces higher or peak flows immediately following storm events.