A French drain is a drainage system used to remove standing water on the ground's surface. In a French drain, a trench directs the water away from an area. This system can be used anywhere on your property where water collects, including around a rock wall. French drains can be added to the ground without any special equipment.
Dig a trench into the ground. Start the trench next to the rock wall where the water is accumulating. The trench should be approximately 6 inches wide and 1 foot deep.
Aim the trench down a slope on your property so that gravity will draw the water naturally away from the wall. The trench should come out somewhere at the edge of your property where it can be left to soak naturally into the ground and will not interfere with anything.
Line the trench with landscape fabric. The fabric will keep the soil from mixing with the gravel and clogging up the drain.
Fill the trench with gravel that is 1/2 inch to 1 inch in diameter. The trench should be filled to 4 to 6 inches from the surface.
Cover the gravel with sand until the sand is level with the ground's surface. Use coarse sand to ensure proper draining.
Lay sod over the top of the sand. This will hide the trench from showing.