The spatial relationship between individual stream courses in an area. The resulting pattern often reflects the underlying rock type and structure, and several varieties are recognized. A dendritic pattern is the most common, characterized by a randomly branched arrangement. It is not structurally controlled, and is developed on a homogeneous rock, e.g. clay. A trellis pattern consists of subparallel streams, usually aligned along the geologic strike, and joined at right angles by tributaries. A rectangular pattern is dominated by right-angled bends, and reflects control by joints or faults. A centripetal pattern consists of stream courses converging into a central depression. The drainage network is the drainage pattern viewed geometrically.