Surface water is drained by flow (migration from the high points to the low point), with typical methods being rivers, canals, and trenches. Flowing water causes erosion as it dislodges and carries soil particles.
Methods devised for draining surface water do not work for draining water below the surface since they are solutions based on flow. Typical solutions offered over the years consist of various shapes of pipe with holes, slots, or perforations of some variety. The flow channels created by the pipes, holes, slots, and perforations are quickly covered over with soil particles carried by the flowing water. Blocked drainage can’t be repaired without a complete excavation and replacement.