There is described a drainage structure for collecting and removing liquid from an area, the drainage structure comprising: a catchment reservoir; an outlet; an outlet orifice located at an interface of the catchment reservoir and the outlet, wherein the outlet orifice enables liquid to flow between the catchment reservoir and the outlet; and an outlet orifice surface arranged adjacent the outlet orifice, the outlet orifice surface comprising at least one protrusion which protrudes into the catchment reservoir and/or the outlet.