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RIVERS AND
ASSOCIATED
LANDFORMS
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Geomorphology
Study of surface features of the Earth, curved byriver; wind or glacial action.
Evolution and structure of various landformsrelated to mountains, plains, plateaus, valleys andbasins are specialized field of study withingeomorphology.
Fluvial Geomorphology
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River
Running water is the most important agent oferosion on the continents and the stream valleys arethe most common landforms.
Rivers flowing to the oceans drain about 68 % ofthe Earth's land surface. The remainder of the landeither is covered by ice or drains to closed basins.
River gradually mould the land by eroding away thematerial in some place and depositing it in other
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A river system consists of a main channel (trunk stream) and all of the
tributaries that flow into it or joining the trunk stream.
A RIVER SYSTEM CAN BE DIVIDED INTO THREE SUBSYSTEMS:
collecting system (branches) -- consisting of a network of tributaries in the
headwater region, collects and funnels water and sediment to the main stream
transporting system (trunk) -- the main trunk stream, which functions as a
channelway through which water and sediment move from the collecting area
toward the ocean. (Erosion and deposition also occur in a river's transporting
system)
dispersing system (roots) -- consists of a network of distributaries at themouth of a river (delta), where sediment and water are dispersed into an
ocean, a lake, or a dry basin
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tributary : a stream flowing into or joining a larger stream
distributary : numerous stream branches into which a river
divides where it reaches its delta
upstream : moves toward headwater (up the regional slope
of erosion)
downstream : moves toward mouth of river (delta)
Delta : a large, roughly triangular body of sediment deposited
at the mouth of a river
Meander : a broad, looping bend in a river Braided : river is divided into multiple channels by alluvial
islands. Braided rivers tend to have steeper gradients
Parts of River
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Irregular branching pattern (tree like)
in many direction. It is common in massive rocks and in flat
lying strata
Due to strong resistance of rocks
headward development of valley is
negligible.
Drainage Pattern
Dendritic
Parallel Parallel or sub-parallel drainage
formed on sloping surface.
Common in terrain with homogeneousrocks.
Development of parallel rills, gullies ornarrow channels are commonly seen ongently sloping surface
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Streams radiates out from the center
of the topograhic high
common in Volcanic terrain
Channels marked by right-angle
bends
Commonly due to presence of joints
and fractures in the massive rocks or
foliation in metamorphic rocks
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Consequent Stream:
A stream following the
slope. Development of
slope may be due to
sudden tectonic uplift
Subsequent Stream:
A stream that develops later on, carving
the softer rocks and flow at almost
right angle to the original slope of the
land
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Stream Order
1
1
2
3
11
2
3
4
1 12
Drainage
Basin
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Alluvial Fan
FLUVIAL LANDFORMS
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Alluvial fans are fan-
shaped deposits of water-transported material(alluvium).
They typically form at thebase of topographicfeatures where there is a
marked break in slope.
Consequently, alluvialfans tend to be coarse-grained, especially at theirmouths. At their edges,
however, they can berelatively fine-grained.
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Braided Channel
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Braided Rivers exhibit numerous channels that split off
and rejoin each other to give a braided appearance. Theytypically carry coarse-grained sediment down a steep
gradient.
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Meandering Pattern
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In contrast to braided rivers, meandering rivers typically
contain one channel that winds its way across the
floodplain. As it flows, it deposits sediment on banks that
lie on the insides of curves (point bar deposits), and erode
the banks on the outside of curves.
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Deltas form wherever rivers encounter standing bodies of water such
as lakes or oceans.
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The Ganges and Brahmaputra Rivers
combined have formed one of the
largest deltas in the world, comprising
approximately 105 640 km2
. The Ganges River originates near the
Tibet/India border, and then flows
southeast across India to combine
with the Brahmaputra in the country
of Bangladesh. The Brahmaputra River has its source
in Tibet along the northern slope of
the Himalayas, and flows across
Assam into Bangladesh. The drainage
basin, approximately 1.6 million km2
in area, is geologically young, with
large volumes of unconsolidated
sediment available for transportBay of Bengal
Ganga
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Young stream Vegetation onlevee
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Levees
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Oxbow lakes
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River system
Headwater
TributariesTrunk streamDistributaries
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