Which type of drainage pattern is found in Maharashtra ?
(a) Dendritic
(b) Parallel
(c) Indefinite
(d) Trellis
Answer options :

Question

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Correct — option (4), All of the above: dendritic, parallel, indefinite and trellis patterns are all met with in Maharashtra. The question is not asking which single pattern characterises the state; it is asking which of the four occur within it, and a state that runs from a narrow coastal strip through a steep north-south mountain wall onto a wide lava plateau has room for all of them. Take them in turn. The dendritic pattern — a trunk stream with tributaries joining it at acute angles like the branches of a tree — develops where the underlying rock offers roughly uniform resistance and no structural line steers the water. That is the ordinary condition over most of the Deccan basalt, and the great east-flowing plateau drainage of the Godavari and Bhima basins takes this branching form. The parallel pattern — a set of streams running side by side in the same direction, joining nothing until they reach base level — develops where the land has a strong uniform slope. The western face of the Sahyadri gives exactly that: the short, swift Konkan rivers drop from the crest to the Arabian Sea down a single steep gradient in a series of roughly parallel courses. The trellis pattern — tributaries meeting the main stream at close to right angles, giving a rectangular, grid-like network — develops where the rock is not uniform but banded, so that streams cut along the weaker bands and cross the harder ones only at gaps; the Deccan lava pile is made of stacked flows of differing hardness and is cut by joints and lineaments, and where those exert control the drainage takes on this angular arrangement. The indefinite pattern is the residual class: drainage that shows no consistent geometry at all, because relief is irregular and neither slope nor rock structure dominates strongly enough to impose a shape. Each of the three partial options excludes one pattern that does occur, so only option (4) is defensible.

Why the other options are wrong — (a) This option accepts dendritic, parallel and indefinite drainage but excludes (d) the trellis pattern. The exclusion is the error. A trellis network forms wherever alternating resistant and less resistant bands, or a set of joints and structural lineaments, force tributaries to run along the weak lines and meet the master stream at nearly right angles — and the Deccan basalt of Maharashtra is a stack of many separate lava flows of unequal hardness, cut by joints, which is precisely the kind of banded, structurally controlled ground that produces angular drainage where the control is strong.  (b) This option drops (a) the dendritic pattern, which is the least defensible omission of the three. Dendritic drainage is the default form a river network takes when the bedrock is broadly uniform and no structure steers it, and it is the commonest pattern in Maharashtra, shown by the long east-flowing plateau rivers of the Godavari and Bhima basins across the Deccan lava country. An answer that admits the specialised patterns while excluding the general one has the geography inverted.  (c) This option drops (b) the parallel pattern, which is the one the state's relief makes most obvious. West of the Sahyadri crest the land falls steeply to the Arabian Sea over a short distance, and the Konkan rivers respond to that single dominant slope by running side by side in the same direction, short and swift, without converging on a common trunk before they reach the sea. A uniform steep slope is the textbook condition for parallel drainage, and Maharashtra's western scarp supplies it along the state's whole coastline.

Concept: A drainage pattern is the plan-view arrangement a river and its tributaries take, and it is read as evidence of what controlled the water as the network cut down. Four controls matter: the direction and steepness of the initial slope, the uniformity of the rock, the presence of structural lines such as joints and faults, and the shape of the relief. Dendritic patterns record the absence of structural control — uniform rock, gentle regional slope, and a tree-like branching network. Parallel patterns record the dominance of a single steep slope, which lines the streams up in the same direction. Trellis patterns record strong structural control by banded rock, producing right-angled junctions and a rectangular grid. Radial patterns record a central high point from which streams run outward, and centripetal patterns the reverse, streams converging into a basin. The residual class the paper calls indefinite covers drainage that fits none of these cleanly, because relief is irregular and no single control is strong enough to shape the network. Because these are responses to conditions rather than fixed properties of a region, one state can display several of them wherever its geology and relief change.

State PCS 2024 Q24 — Geography PYQ with Answer

State PCS 2024 Q24 — Geography PYQ with Answer