Civil Engineering · Engineering Glossary
Site drainage is the engineered system of graded surfaces, swales, inlets, pipes, and detention or retention facilities that collects and conveys stormwater runoff from a developed site to an approved outfall. Proper drainage design prevents flooding, erosion, and property damage while complying with local stormwater regulations.
Site drainage design begins with hydrology — calculating the runoff from the site for the design storm event (typically the 10-year or 100-year storm, depending on jurisdiction). The civil engineer designs swales, channels, inlets, and underground storm sewer pipes to convey the design flow without overtopping. Detention basins temporarily store runoff and release it slowly to limit peak flows to pre-development rates, which is typically required by local stormwater management ordinances. Retention ponds permanently store runoff for infiltration or evaporation. Low Impact Development (LID) techniques — bioretention, permeable pavement, green roofs — reduce runoff through infiltration and evapotranspiration. Apex Grid designs site drainage systems for commercial, industrial, and multifamily development.
Apex Grid Engineering maintains this glossary as a resource for architects, contractors, developers, and property owners who encounter unfamiliar engineering terminology on their projects.
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