A dendritic drainage pattern is the most common form and looks like the branching pattern of tree roots. It develops in regions underlain by homogeneous material. That is, the subsurface geology has a similar resistance to weathering so there is no apparent control over the direction the tributaries take.
Quick Answer. A trellis drainage pattern occurs when tributaries join a river and erode a valley at right angles in a pattern that resembles a garden trellis. Drainage patterns occur most often where rock or other soil formations can erode easily along weak areas in the rock.