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.
There are three other different types of drainage patterns caused by rainfall:
- Dendritic: This is the most common type of drainage pattern where it develops on top of land where the rock is uniformly resistant to erosion.
- Radial:Develops in high elevations that drop to lower areas.
- Rectangular: Develop at linear zones of weakness including joints and faults.