Solving Backyard Drainage with French Drains and Check Dams

Diagnosing a Perpetually Wet Slope Base

Water from the uphill neighbor seeps downslope, overwhelming an undersized or poorly placed drain pipe. The pipe may be too small, lack sufficient slope, or the soil permeability is too low for water to reach it quickly.

Improvements

• Check dams on the slope or a shallow basin at the base slow runoff, giving the drain time to capture water.
• French drain with gravel to the surface (no soil cover) increases infiltration area.
• Swale with underdrain (perforated pipe + catch basins/drywells) handles larger volumes.
• Increase pipe diameter or add parallel lines if flow exceeds capacity.

Key Principle

Slow the water down, spread it out, and give it a clear path to an outlet. A single 4-inch pipe 8–10 inches deep is often inadequate for sustained seepage.