Drainage Patterns: Dendritic, Trellis, Radial & More
Complete guide to drainage patterns in geography covering dendritic, trellis, rectangular, radial, centripetal, annular, deranged, and barbed patterns with Indian and world examples for UPSC.
A drainage pattern is the spatial arrangement of streams in a region, shaped by slope, rock structure, geological history, and climate. Reading drainage patterns on a topographic map tells you about the underlying geology before you even look at a geological map. UPSC tests this concept in both Prelims (matching pattern to geological structure) and GS-I Mains (Indian drainage systems).
The pattern a river network forms is never random. It is a direct expression of the rocks and structures beneath. Master the 8 major patterns, and you can decode landscapes.
Major Drainage Patterns
1. Dendritic Pattern
The most common drainage pattern worldwide. Streams branch irregularly in all directions, resembling a tree's branches ("dendron" = tree in Greek). Forms on uniform, horizontally-bedded rock with no structural control — the streams follow the slope without being deflected by resistant rock layers.
Where found: Indo-Gangetic Plain (tributaries of the Ganga on flat alluvial terrain), upper peninsular rivers on the Deccan Trap basalt, Mississippi River basin, Amazon basin.
The Ganga's tributaries — Gomti, Ghaghra, Gandak, Kosi — create a textbook dendritic pattern on the northern plains because the alluvium offers uniform resistance in all directions.
Diagnostic clue: Irregular branching at acute angles. No preferred orientation of tributaries.
2. Trellis Pattern
Main streams flow parallel to each other, controlled by alternating bands of resistant and weak rock. Short tributaries join at near-right angles from the sides. The name comes from a garden trellis (lattice framework).
Where found: Folded mountain regions where valleys follow soft rock (synclines or weak beds) and ridges form on hard rock. Appalachian Mountains (USA) is the textbook global example. In India, parts of the Jhelum system in the Kashmir Valley and the Subarnarekha River in Jharkhand show trellis tendencies.
Diagnostic clue: Parallel main streams with short, right-angle tributaries. Strong structural control visible.
3. Rectangular Pattern
Streams and tributaries make right-angle bends, following a joint or fault system in the bedrock. Different from trellis because both main streams and tributaries change direction at right angles, not just the junction point.
Where found: Regions with a well-developed joint/fault system in two perpendicular directions. Parts of the Colorado Plateau (USA), Scandinavian Shield, and some sections of the Vindhyan region in central India.
Diagnostic clue: Streams make sharp 90-degree bends, creating a blocky, angular network.
4. Radial Pattern
Streams flow outward from a central high point in all directions, like spokes of a wheel. Develops on volcanic cones, domes, or residual hills.
Where found: Amarkantak Plateau (Madhya Pradesh) — one of India's finest examples. From this single plateau, three major rivers radiate: Narmada flows west, Son flows north (to join the Ganga), and Mahanadi flows east to the Bay of Bengal. Mount Kilimanjaro (Tanzania), Mount Etna (Italy), and the Ozark Dome (USA) are global examples.
Also visible around isolated residual hills in the Deccan, where small streams radiate outward from granite inselbergs.
Diagnostic clue: Streams diverge from a central point in multiple directions.
5. Centripetal Pattern
The reverse of radial — streams flow inward toward a central depression or basin. Think of water draining into a sinkhole or lake.
Where found: Loktak Lake (Manipur), where surrounding streams converge into the lake. Crater lakes, karst sinkholes, tectonic basins. Lake Chad (Africa) and the Great Basin (Nevada, USA) are global examples. The Sambhar Lake in Rajasthan also shows centripetal drainage from the Luni catchment.
Diagnostic clue: Streams converge toward a low point instead of diverging toward the sea.
6. Annular Pattern
Streams arrange in a ring-shaped (annular) pattern, following concentric bands of alternating hard and soft rock in an eroded dome structure. Main streams occupy the weak rock belts; short tributaries cut across the resistant bands.
Where found: Eroded structural domes where differential erosion has exposed concentric rock layers. Black Hills of South Dakota (USA) is the classic example. In India, Pithoragarh district (Uttarakhand) shows partial annular patterns in eroded gneissic domes.
Diagnostic clue: Ring-shaped stream segments connected by short radial links.
7. Deranged Pattern
An irregular, chaotic network with no discernible pattern. Streams wander without structural or slope control, forming poorly integrated drainage with many lakes, swamps, and dead ends.
Where found: Recently deglaciated areas where ice sheets disrupted the pre-existing drainage. The Canadian Shield, Finland, and parts of Ladakh where glacial retreat left behind disorganized drainage.
Diagnostic clue: No pattern. Lots of lakes, marshes, and disconnected channels.
8. Barbed Pattern
Tributaries flow in the opposite direction to what the regional slope suggests, joining the main stream at obtuse angles (pointing upstream). This indicates river capture (stream piracy) — a more powerful stream has captured the headwaters of a weaker stream, reversing tributary flow direction.
Where found: Where an aggressive river has breached a divide and captured drainage from an adjacent basin. Parts of the Tista River system in Sikkim-West Bengal and some Himalayan tributaries show barbed patterns due to tectonic river capture.
Diagnostic clue: Tributaries point upstream instead of downstream. Hook-shaped junctions.
Drainage Patterns: Comparison Table
| Pattern | Shape Description | Geological Cause | Indian Example | World Example |
|---|---|---|---|---|
| Dendritic | Tree-branch, irregular | Uniform rock, no structural control | Ganga tributaries on alluvial plain | Mississippi, Amazon |
| Trellis | Parallel mains, right-angle tributaries | Folded rocks, alternating hard-soft bands | Jhelum in Kashmir | Appalachians (USA) |
| Rectangular | Right-angle bends in all streams | Perpendicular joint/fault systems | Parts of Vindhyan region | Colorado Plateau |
| Radial | Outward from central high point | Volcanic cone, dome, residual hill | Amarkantak (Narmada/Son/Mahanadi) | Mt. Kilimanjaro |
| Centripetal | Inward to central depression | Basin, crater, tectonic low | Loktak Lake (Manipur) | Lake Chad (Africa) |
| Annular | Ring-shaped segments | Eroded dome, concentric rock bands | Pithoragarh (partial) | Black Hills (USA) |
| Deranged | Chaotic, no clear pattern | Recent glaciation, disrupted drainage | Parts of Ladakh | Canadian Shield |
| Barbed | Tributaries point upstream | River capture/stream piracy | Tista system (partial) | Various captured streams |
Indian Drainage: Key Concepts
Peninsular vs. Himalayan Rivers
Understanding India's drainage requires distinguishing between two fundamentally different river systems:
Himalayan rivers are antecedent — the Indus, Satluj, and Brahmaputra established their courses before the Himalayas rose and maintained them by cutting deep gorges as the mountains uplifted. This is why these rivers flow across (not around) the Himalayas, creating transverse gorges thousands of meters deep.
Peninsular rivers are consequent — they follow the slope of the land surface. The Western Ghats form the principal water divide. Most peninsular rivers (Godavari, Krishna, Kaveri, Mahanadi) flow eastward into the Bay of Bengal. Only the Narmada and Tapi flow westward through rift valleys, not because of slope but because they occupy graben (downfaulted troughs) between the Satpura and Vindhya ranges.
Common student mistake: Claiming Narmada flows west because the Western Ghats slope that way. Wrong. The Narmada flows through a rift valley (tectonic origin). The reason is structural, not slope-based. The Western Ghats are higher on the west, which is precisely why most rivers flow east.
Watershed and Drainage Divide
A watershed (or drainage divide) separates two adjacent river basins. The Western Ghats form India's most important watershed, separating the short, swift west-flowing rivers from the longer east-flowing rivers.
India has 12 major river basins (catchment area >20,000 sq km) and 46 medium river basins (2,000-20,000 sq km). The Ganga basin is the largest at 8,61,452 sq km (26.2% of India's area), draining parts of 11 states.
Superimposed and Antecedent Drainage
Antecedent rivers (already discussed) maintained their course despite tectonic uplift. Superimposed drainage occurs when a river establishes its course on a younger rock layer, then erodes down to expose an older layer with different structure — but the river ignores the new structure and keeps its old course. The Damodar River cutting across the Rajmahal Hills shows superimposed drainage characteristics.
UPSC Relevance
UPSC Prelims 2017 asked about rivers originating from Amarkantak — a direct test of the radial drainage concept. Mains GS-I frequently asks "Compare Himalayan and Peninsular rivers" or "Explain why Narmada and Tapi flow westward." Geography Optional tests all 8 drainage patterns with diagram-based questions.
Draw diagrams for each pattern. UPSC Mains rewards labeled diagrams, and drainage patterns are among the easiest to draw accurately.