i. Landforms Made By Running Water
There are two components of running water –
- Overland flow on the general land surface as a sheet.
- Linear flow as streams and rivers in valleys.
Most of the erosional landforms made by running water are associated with vigorous and youthful rivers flowing over steep gradients and the gentler the river channels in gradient or slope, the greater the deposition.
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Erosional landforms |
Depositional landforms |
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1. Valleys – Valleys start as small and narrow rills; the rills will gradually develop into long and wide gullies; the gullies will further deepen, widen and lengthen to give rise to valleys. Eg. V-shaped valley, canyon, etc 2. Gorge – It is a deep valley with very steep to straight sides. 3. Potholes and Plunge pools – Potholes are formed because of stream erosion aided by the abrasion of rock fragments. At the foot of waterfalls, large potholes, quite deep and wide, form, and such potholes are called plunge pools. 4. Incised or Entrenched Meanders – They are very deep wide meanders (loop-like channels) found cut in hard rocks. 5. River Terraces – They result due to vertical erosion by the stream into its own depositional floodplain. |
1. Alluvial fans – When the stream moves from the higher level and breaks into a foot slope plain of a low gradient, it loses the energy needed to transport much of its load. Thus, they get dumped and spread as broad low to high cone-shaped deposits called alluvial fans. 2. Deltas – Deltas are like alluvial fans but develop along the coast. 3. Floodplains – Large-sized materials are deposited first when a stream channel breaks into a gentle slope. A riverbed made of river deposits is an active floodplain. 4. Natural levees – Natural levees are low, linear, and parallel ridges of coarse deposits along the banks of rivers. When rivers shift laterally, a series of natural levees can form. 5. Point bars – For large rivers, the sediments are deposited in a linear fashion at the depositional side of a meander. 6. Braided Channels – When selective deposition of coarser materials causes the formation of a central bar, it diverts the flow of the river towards the banks, which increases Lateral erosion. Similarly, when more and more such central bars are formed, braided channels are formed. |
Note: Meanders – Meanders are loop-like channel patterns developed over the flood and delta plains. They are actually not a landform but only a type of channel pattern formed as a result of deposition.
As meanders grow into deep loops, the same may get cut off due to erosion at the inflexion point and are left as oxbow lakes.