Soils that have dense, fine-textured subsoils and claypan soils are very slowly permeable. Their structure is coarse, angular blocky or massive with very few visible pores. Roots are few and generally follow ped faces and cracks. These subsoils are very firm when moist and very hard when dry. Soil peds have thick, continuous, clay films on surfaces.
Horizontal cracks are longer than vertical ones.
Surface Runoff Surface runoff is the relative rate water is removed by flowing over the soil surface. This includes rainfall, as well as water from adjacent slopes. It is the combined effect of soil slope, position in the landscape, permeability, and infiltration rate on runoff. Four classes of runoff are recognized in Oklahoma land judging. A large amount of rainfall is lost and only a small portion moves into the soil increasing the erosion hazard.