My backyard is flat about 14 feet out & then goes up a bank thats rather steep for the riding mower. Its rideable, but a little intense. I'd like to build an interlocking block retaining wall about 3-4 ft high at the base to make it a little better & put a patio up to the wall. I've read how to put the drainage pipe in the back of the wall. However, I'm not sure how to drain the water running from the house side of the wall. I've got a slight slope away from the house all the way around to run water from the house. Its not a lot of water, but it needs to go somewhere when it rains heavy. My question is, does it just seep thru the wall & into the same drain or will it need ditched on the front side of the wall?