Lawn Care/Maintenance/Drainage
Surface and subsurface drainage are essential to maintain turfgrass. Primary reasons for good drainage include:
Surface drainage is the removal of excess runoff from rainfall, irrigation, seeps, or springs by water flowing on the soil surface. Surface drainage allows for removal of much larger volumes of water in a shorter time span than subsurface drainage. Two approaches can be followed when working with surface drainage. The first is to divert water away using turf lined channels before it can collect in low spots. The channel should leads to a natural outlet such as a road ditch where the excess water can be handled properly. The second, less desirable, approach is to provide a channel to drain water from the low spot after it collects.
Random drains are commonly used to drain scattered low spots that are not removed during construction. Drainage channels are used to link these low spots and then the water is channeled to an outlet. The drainage channels should follow the natural lay of the land.
Channel cross section
Diversions divert water away from specific features as bunkers, flower beds, or adjacent properties. They are useful for short irregular slopes. Thick turf should be maintained in the channel to prevent erosion, slow velocity of runoff, and trap eroded soil particles.
Subsurface drainage is the removal of excess water from soil. Water in soil moves to through the soil to the drain tile, but this is a slow process compared to surface drainage. Various arrangements of drains are used depending on the situation.
Grid systems are used to drain areas of uniform slope where the entire area requires drainage.
Interceptor drains are used to drain areas that are wet due to seepage from a hillside. The drain tile should be placed at the depth of the impermeable layer if possible.
Subsurface drain lines are designed to remove excess water from soil. The groundwater enters the tile through openings cut in the tile along the entire length of the line.
Two methods are used to divert surface water into the drain tile. The simplest is to backfill the open trench with gravel or other coarse material over the tile. This works well but the gravel can become clogged with silt and clay over time. The second type of inlet is an inlet structure that extends to the soil surface where it is covered with a grate. Surface inlets work best where large quantities of water are to be removed.
Tile outlets are critically important when installing subsurface drainage. Common problems include clogged outlets from weeds and debris, animal nests in the tile line, broken or crushed outlet lines, and soil erosion around the outlet. These problems can be prevented by properly constructing the outlet initially and with regular maintenance. The last 10-15 feet of the outlet should be metal pipe. The drain tile-metal pipe connection should be cemented in place beneath the soil for stability. The drain tile should not be extended to the outlet point.
