Soil surfaces should always slope away from buildings. Low areas sometimes cause problems because they cannot easily be graded to provide for adequate surface drainage. In such cases, drainage channels or underground drains may need to be constructed. Good internal drainage, which is the movement of water through the soil, will influence the effective rooting depth and resulting plant vigor. Many landscapes remain internally saturated because of underlying clay and rock layers.
Sandy soils are generally well drained, but can be subject to dryness.
Frequent light watering may be required because of their low water-holding capacities. Internal drainage should be good on deep soils with sloping surfaces. Layers that restrict downward water movement, however, may cause poor internal drainage, even on slopes. This generally appears as a down-slope damp or soggy condition showing at the ground surface. Obviously, rooting conditions and plant vigor are adversely affected in such areas.