Direct runoff
"That part of surface runoff which reaches the catchment outlet immediately after the rain starts. Its volume is equal to rainfall excess. Some procedures for its derivation include prompt subsurface runoff but all exclude base flow." (United Nations Publications, 2013)
Sources
United Nations Publications. "Glossary of Shared Water Resources (English-Arabic): Technical, Socioeconomic and Legal Terminology." (2013). DOI:https://dx.doi.org/10.18356/70b462ce-en