Drainage Patterns: Descriptive and Genetic Classifications

1. Drainage System vs. Drainage Pattern

In fluvial geomorphology, two fundamental concepts are often confused but must be kept distinct:

2. Open Geomorphic System Framework

A drainage basin operates as an open geomorphic system, receiving inputs (precipitation, solar energy) and releasing outputs (water, sediment) through its mouth.

Key concepts:

• Ultimate Base Level — Sea level; the lowest point to which an exterior-draining river can erode.
• Regional / Temporary Base Level — In endorheic (closed) basins, streams terminate in inland lakes or desert playas. A resistant rock layer also acts as a temporary base level.
• Drainage Divide — The ridge separating adjacent basins. Sharp in young topography (Himalayas); indistinct in old, peneplained landscapes (Deccan Plateau).

3. Quantitative Morphometry

4. Genetic Classification of Streams

Geomorphologists classify streams by their relationship to initial slopes and geological structures into two broad groups:

A. Sequent / Accordant Streams

Streams that strictly follow regional tectonic slopes and geological structures.

1. Consequent Stream (Dip Stream)
The first stream to form on a newly uplifted surface. Flows directly down the initial regional slope and bedrock dip.

• Indian Examples: Godavari, Krishna, Cauvery descending from the Western Ghats to the Bay of Bengal. 2. Subsequent Stream (Strike Stream) Develops after the consequent stream by headward erosion along soft rocks parallel to the geological strike.
• Indian Examples: Asan and Song rivers along the Dehradun strike valley; Chambal, Sind, Ken, Betwa, Tons, Son rivers joining Yamuna-Ganga at near-right angles. 3. Obsequent Stream (Anti-Dip Stream) Flows opposite to the consequent direction, typically from scarp slopes of cuestas and hogbacks.
• Indian Examples: Northward-flowing streams from the Mahabharat/Siwalik Range joining subsequent rivers like the Sun Kosi. 4. Resequent Stream (New Consequent) Flows in the same direction as the consequent but at a lower topographic level, after relief inversion.
• Global Example: Synclinal streams in the Appalachian Ridge and Valley province.

B. Insequent / Discordant Streams

Streams that cut directly across folds, faults, and mountain barriers.

1. Antecedent Drainage (Inconsequent)
A stream older than the mountains across its path. The river maintained its course by cutting downward as the land rose around it.

• Indian Examples: The Indus, Brahmaputra, and Sutlej — all older than the Himalayas, cutting deep, narrow gorges. The Indus gorge near Gilgit reaches ~17,000 feet deep. 2. Superimposed Drainage (Epigenetic / Superposed) A stream that initially developed on younger overlying strata and was lowered onto older, structurally discordant formations through continuous erosion.
• Indian Examples: Damodar and Subarnarekha in Chotanagpur Plateau; Son River cutting across Khainjua ridges at Deoland; rivers of Rewa and Bhander Plateaus.

5. Descriptive Drainage Patterns

1. Dendritic Pattern 

Shape: Irregularly branching, tree-like network. Tributaries join the trunk at acute angles (less than 90°).

Controls:

• Homogeneous lithology with uniform rock resistance (isotropic conditions)
• Absence of significant faulting, jointing, or folding
• Flat to gently rolling topography Formation: Three phases — Open Dendritic (youth) → Closed Dendritic (maturity) → Simplified Dendritic (old age via river capture) Indian Examples: Mahanadi, Godavari, Krishna, Cauvery, Damodar; Indo-Gangetic plains; Rajasthan desert plains; Vindhyan sandstone plateaus (Panna, Bhander, Rewa); Ranchi Plateau (granite-gneiss). Global Examples: Canadian Shield; Russian Platform; Northern European glaciated lowlands. Exam Key: Bifurcation Ratio (Rb) in dendritic basins = 3.0–4.5 — reflects pure random branching with no structural control.

2. Trellis Pattern

Shape: Grid-like lattice. Long parallel strike streams joined by short lateral streams at strict right angles (90°).

Controls:

• Strongly folded rocks (parallel anticlines and synclines)
• Alternating resistant (quartzite, sandstone) and weak (shale) rock bands
• Cuesta or hogback topography Formation: Consequent streams occupy synclinal troughs; subsequent tributaries erode headward along soft strike vales at 90°. Indian Examples: Singhbhum region, Chotanagpur Plateau. Global Examples: Appalachian Ridge and Valley (USA); Jura Mountains (Europe); Paris Basin (France). Exam Key: Longitudinal streams = subsequent (strike) streams; short perpendicular streams = dip (consequent/resequent) and anti-dip (obsequent) streams.

3. Rectangular Pattern 

Shape: Blocky, orthogonal network with sharp right-angled bends and perpendicular confluences.

Controls:

• Orthogonal joint sets, fractures, or perpendicular fault planes
• Uniform lithology with pronounced structural lines of weakness
• Flat to moderate slopes (no folded ridges) Formation: Runoff exploits orthogonal joint networks, creating intersecting perpendicular linear depressions. Indian Examples: Vindhyan Mountains; Belan River (UP/MP border) and its tributaries (Adwa, Naina) along Upper Vindhyan sandstone joints. Global Examples:

  Shape: Multiple streams originate at a central elevated point and flow outward in all directions (like spokes of a wheel).

  Controls:

  • Domal uplifts, laccoliths, volcanic cones
  • Centralized tectonic uplift creating radially outward gradients Formation: Tectonic uplift or volcanic construction forces runoff outward along the steepest radial slopes. Indian Examples: Amarkantak Hills (source of Narmada, Son, Mahanadi); Ranchi Plateau dome (South Koel, Subarnarekha, Kanchi, Karo); Girnar Hills (Gujarat); Mikir Hills (Assam); Rohtas Plateau (SW Bihar). Global Examples: Mt. Kilimanjaro (Africa); Sri Lanka Central Highlands; Central French Plateau. Note: If a dome is deeply eroded, radial streams may evolve into an annular pattern as concentric subsequent streams develop in the circular vales.

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  5. Centripetal Pattern 

  Shape: Multiple streams converge inward toward a central low point — the geometric opposite of radial.

  Controls:

  • Enclosed structural depressions, synclinal basins, downfaulted grabens, volcanic calderas
  • Interior drainage with no outflow to the sea (endorheic) Formation: Tectonic subsidence or volcanic collapse creates an enclosed basin; runoff is forced inward toward the center. Indian Examples: Closed basins of Ladakh (Himalayas); Raigarh Dome depression, Lower Chambal Basin. Global Examples: Kathmandu Valley (Nepal); Closed basins of Tibet; Caspian Sea basin; Lake Aral; Lake Chad. Exam Key: Centripetal drainage in arid regions forms playas (flat salt-encrusted lake beds) due to intense evaporation of the ponded water.

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  6. Annular Pattern 

  Shape: Subsequent tributaries flow in concentric, arcuate rings around a central summit before joining outward-radiating streams.

  Controls:

  • Maturely dissected structural dome (breached dome)
  • Alternating concentric bands of resistant (sandstone, quartzite) and weak (shale) rocks
  • Creates concentric circular cuesta ridges and circular strike vales Formation: Differential erosion breaches a dome's outer layers, exposing circular strata. Subsequent streams exploit circular weak-rock vales, adopting curved concentric paths. Indian Examples: Sonapet Dome, Chotanagpur Plateau (Jharkhand) — most famous Indian example; Pithoragarh (Uttarakhand); Nilgiri Hills (Tamil Nadu and Kerala). Global Examples: Black Hills, South Dakota (USA); Weald dome, southeast England. Key Distinction from Radial: Radial = straight outward lines. Annular = concentric circular rings. Annular is a structurally more mature stage of radial drainage on a deeply eroded dome.

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  7. Parallel Pattern 

  Shape: Numerous independent channels running parallel or sub-parallel, rarely merging, flowing directly into the sea or sink.

  Controls:

  • Pronounced, uniformly steep, unidirectional regional slope
  • Linear fault scarps or dipping homoclinal strata
  • Uniform lithology with rapid downslope runoff Formation: Tectonic uplift or coastal emergence forces runoff into straight, parallel consequent channels before lateral convergence can occur. Indian Examples: Short, swift rivers descending from the western flanks of the Western Ghats to the Arabian Sea; rivers of Eastern Coastal Plains; source streams of the Adwa River (Kaimur range). Global Examples: Newly emerged coastal "land of a thousand lakes"); Canadian Shield; Minnesota till plains. Exam Key: Deranged drainage = direct proof of recent continental glaciation and extreme geomorphic youth of the current fluvial cycle.

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  6. Bonus Patterns

  A. Barbed Pattern 

  Tributaries join the master stream at backward-pointing, hook-shaped junctions — result of river capture (stream piracy) and tectonic flow reversal. Tributaries continue in their original direction while the trunk stream reverses.

  • Indian/Himalayan Example: Arun River (tributary of Kosi system), Nepal.

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  B. Pinnate Pattern 

  Dozens of short, closely spaced parallel tributaries join a straight central stream at extremely acute angles, resembling feather veins. Controlled by narrow linear valleys flanked by steep parallel ridges.

  • Indian Example: Upper reaches of the Son and Narmada rivers in tectonically constrained rift-valley trenches.

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  C. Herringbone / Rib Pattern 

  Short parallel tributaries join a straight central longitudinal stream at near-right angles, like fish ribs. Controlled by broad U-shaped valleys or structural trenches bordered by steep parallel ridges.

  • Indian Examples: Upper Jhelum River (Vale of Kashmir); Tamar Kosi; upper Rapti River.

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  D. Angular Pattern 

  Tributaries join at oblique (acute or obtuse) angles, creating zig-zagging courses. Controlled by oblique (non-perpendicular) intersecting joint or fault sets.

  • Indian Example: Complex fractured terrains of the Himalayan foothill regions.

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  7. Comparative Summary Tables

  Table 1: All Major Drainage Patterns at a Glance

  Pattern	Shape	Primary Control	Indian Example	Global Example
  Dendritic	Tree-like, acute junctions	Homogeneous lithology; no folds/faults	Godavari, Mahanadi, Ganga	Canadian Shield
  Trellis	Perpendicular junctions; parallel strike channels	Folded strata; cuesta/hogback	Singhbhum, Chotanagpur	Appalachian Ridge and Valley
  Rectangular	Blocky, right-angled bends	Orthogonal joints/faults	Vindhyan Mts.; Belan River	Colorado River
  Radial	Centrifugal spokes from central hub	Domed/volcanic structures	Amarkantak Hills; Ranchi Plateau	Mt. Kilimanjaro
  Centripetal	Inward converging channels	Enclosed depressions; grabens	Ladakh basins; Raigarh Dome	Kathmandu Valley
  Parallel	Long, straight, non-merging channels	Steep regional slope; fault scarps	Western Ghats rivers (Arabian Sea)	South American west coast
  Annular	Concentric circular rings	Breached domes; alternating strata	Sonapet Dome (Jharkhand)	Black Hills, South Dakota
  Deranged	Chaotic channels, lakes, bogs	Disrupted glacial drift	Karakoram glaciated valleys	Canadian Shield; Finland
  Barbed	Backward hook junctions	River capture; flow reversal	Arun River (Kosi tributary)	Appalachian streams
  Pinnate	Feather-like, leaf-vein	Narrow valleys, steep ridges	Upper Son and Narmada	American Southwest canyons
  Herringbone	Perpendicular ribs along spine	Broad structural trenches	Upper Jhelum (Vale of Kashmir)	Tamar Kosi; upper Rapti

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  Table 2: Pattern vs. Controlling Factors

  Pattern	Lithological Control	Tectonic / Structural Control	Slope / Topographic Control
  Dendritic	Uniformly resistant rocks	Undisturbed, horizontal strata	Flat to moderate gradients
  Trellis	Alternating hard and soft bands	Intense compressional folding	Folded ridge-and-valley
  Rectangular	Homogeneous; highly jointed	Orthogonal joint/fault grids	Flat, no linear ridges
  Radial	Uniform volcanic / crystalline	Centralized doming / volcanic	Conical or dome-shaped peak
  Centripetal	Variable; flanking a closed basin	Graben faulting; caldera collapse	Enclosed inward-sloping basin
  Parallel	Uniform, homogeneous	Fault block scarps; tilted cuestas	Pronounced unidirectional slope
  Annular	Alternating concentric bands	Breached sedimentary dome	Concentric cuesta ridges
  Deranged	Buried under glacial drift	Disrupted pre-existing bedrock	Hummocky post-glacial plains

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  8. Key Facts for Rapid Revision

  • Consequent = Dip stream | Subsequent = Strike stream | Obsequent = Anti-dip stream | Resequent = New Consequent
  • Asan River (Yamuna) and Song River (Ganga) = classic subsequent streams in the Dehradun strike valley.
  • Indus, Sutlej, Brahmaputra = antecedent rivers older than the Himalayas.
  • Indus gorge near Gilgit = ~17,000 feet deep antecedent gorge.
  • Damodar, Subarnarekha, Chambal, Banas = classic superimposed (epigenetic) drainage.
  • Subarnarekha superimposed on Dalma and phyllite hills west of Chandil (Jharkhand).
  • Son River cuts across Khainjua quartzite ridges at Deoland — classic superimposed feature.
  • "Superimposed drainage" coined by J.W. Powell (1857); "superposed" by W.J. McGee (1888).
  • Horton (1945) — Drainage Density: Dd = L/A.
  • Dakota Badlands (USA) = highest drainage density: more than 125 km/km².
  • Savindra Singh (1976) — Drainage Texture Index (Dt); correlation with Dd exceeds 0.9.
  • Bifurcation Ratio (Rb) in dendritic basins: 3.0–4.5.
  • Gravelius (1914): trunk stream = 1st order (opposite of modern schemes).
  • Strahler (1952): modified Horton's ordering; two 1st-order streams join to form a 2nd-order stream.
  • First systematic Indian drainage basin morphometry: Belan River — Renu Srivastava (1976), Allahabad University.
  • Sonapet Dome (Jharkhand) = most famous Indian annular drainage example.
  • Amarkantak Hills = most famous Indian radial drainage (Narmada, Son, and Mahanadi all diverge from here).
  • Arun River (Kosi tributary, Nepal) = classic barbed pattern from river capture.
  • Vale of Kashmir / Upper Jhelum = classic herringbone pattern.
  • Parallel drainage = initial/youthful pattern that evolves into dendritic or trellis over time.
  • Deranged drainage = evidence of recent continental glaciation.
  • Centripetal drainage in arid zones forms playas (flat, salt-encrusted dry lake beds).
  • Annular = structurally more mature than radial; forms on breached and dissected domes.