The purpose of this Engineering Practice is to provide planning, design, construction and maintenance information and criteria for agricultural drainage outlets by means of open channels. Drainage, so provided, will enhance agricultural production and protect environmental resources. This Engineering Practice is compatible with ASAE EP302, Design and Construction of Surface Drainage Systems on Agricultural Lands in Humid Areas, ASAE EP480 Design of Subsurface Drains in Humid Areas, and ASAE EP481, Construction of Subsurface Drains in Humid Areas.