Why dig a French drain instead of just an uncovered, unfilled trench ?
The reasons for the suggestions are mainly twofold: 1) allows for the slow dissipation of water and eliminates erosion 2) to prevent a breeding ground for mosquitoes French drains often include corrugated drainfield plastic tubing [4-6″] that is surrounded on 4 sides with the gravel. This lets the water traverse a longer/larger area and helps to prevent a saturated or soggy section of land near the point of water entry. Also consider covering the gravel with a mesh material so that dirt doesn’t compact around the rock. the tubing and mesh are found in the same section at Home D or any building supply. Might also consider using “drainfield” rock, which is larger than gravel.
