CORE UNIT: PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT 2. Trellis pattern
In this pattern, tributaries join the main river at right angles, forming a pattern similar to a garden-wall trellis. These patterns form when the main stream flows across landscapes with bands of
hard and soft rock. Smaller tributaries cut their valleys in the bands of soft rock. They then join the main river at right angles. Many glaciated valleys also have this pattern. Streams flow down steep valley
sides from hanging valleys into the main valley with little space to meander across before reaching the main river.
Tributaries join main stream at right angles
Main river
Fig. 9 Trellis drainage pattern shows tributaries joining the main river at right angles.
Fig. 10 Trellis drainage pattern 280 290 300 315
3. Radial pattern This pattern forms when rivers flow in many directions away from an upland area, much like water flowing off an umbrella. The rivers radiate out froma central upland area. Round or oval- shaped hills show this best, for example Brandon Hill in County Kilkenny.
Fig. 11 Radial drainage pattern: rivers flow from a central upland area.