Site & Civil / Subsurface drainage trench
French drain
/frɛntʃ dreɪn/noun
Named after Henry Flagg French, who described it in his 1859 book Farm Drainage.
Definition
A gravel-filled trench, usually containing a perforated pipe wrapped in filter fabric, that collects groundwater and carries it away by gravity.
Fig. 100 — French drain: schematic studyNOT TO SCALE
Illustrative study — French drain · AI-generatedSAMPLE IMAGE
Photo study — French drain · AI-generated00:06
Structural & construction notes
Placed along footings or behind retaining walls, it relieves water pressure on below-grade walls. The pipe needs a steady fall to a daylight outlet or drain, and cleanouts allow flushing.
An educational reference. Project-specific design requires professional guidance.