Goh Cheng Leong Chapter 5: Landforms made by Running Water YouTube Lecture Handouts

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Watch video lecture on YouTube: Goh Cheng Leong Chapter 5: Landforms made by Running Water Goh Cheng Leong Chapter 5: Landforms Made by Running Water
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Development of River System

  • Denudation – general lowering of the surface

  • Erosion + transportation helps this process

  • Rainfall occurs – some evaporates and other runs off in rivers

Watch video lecture on YouTube: Hydrological Cycle or Water Cycle - In 9 Simple Stages Hydrological Cycle or Water Cycle - in 9 Simple Stages
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  • Glaciers and snow only in cold areas, wind mainly in desert, waves in coastal areas but water action is present everywhere

  • Running water is single most important agent of denudation

  • Source – river, lake, marsh usually an upland with heaviest precipitation and slopes down

  • Uplands form the catchment area

  • Crest of mountain is divide or watershed from which streams flow down the slope

  • Consequent stream – initial stream exists as consequence of slope

Joined by tributaries at right angle or obliquely

If rocks are homogenous and of uniform resistance to erosion, tributaries join obliquely as in sequent streams

Drainage can be

  • Dendritic or tree-like: homogenous rock of equal resistance

  • Trellised or rectangular in alternate hard and soft rock

Watch video lecture on YouTube: Restless Rivers - Stream Types, River Capture and Drainage Patterns Restless Rivers - Stream Types, River Capture and Drainage Patterns
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Mechanism of Humid Erosion

Mass movement due to lubricating action of water

  • Soil creep – slow

  • Landslide – sudden

Process of River Action

  • Solution – dissolved (50 tons/year)

  • Suspension – suspended (200 tons/year)

  • Traction Load – coarse material rolled along the bed

  • Mississippi River drains half the size of USA daily into Gulf of Mexico

  • Ability of river to move depends on volume of water, velocity of water, size, shape and weight of load

  • By doubling velocity, transportation power is increased by nearly 10 times

River Erosion & Transportation

Watch video lecture on YouTube: Life Cycle of a River - Stream Orders, Erosion, Transportation and Deposition Life Cycle of a River - Stream Orders, Erosion, Transportation and Deposition
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  • Corrasion or abrasion – mechanical grinding against banks and bed of river – lateral (sideways) or vertical (downwards)

  • Corrosion or solution: chemical or solvent action mainly in calcium carbonate in limestone

  • Hydraulic action: mechanical loosening of material, undermines the softer rocks

  • Attrition: wear and tear of material when they collide with one another, angular pebbles are smoothened into round pebbles

Course of River

Upper (youth)

Watch video lecture on YouTube: Tenacious Rivers - 5 Major Fluvial Erosional Landforms Tenacious Rivers - 5 Major Fluvial Erosional Landforms
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  • Vertical Corrasion

  • V Shaped valley

  • Gorges (Steep and narrow) – Indus gorge in Kashmir

  • Canyons – arid areas – cut deep into valley floor Bryce Canyon, Utah

  • Stream A would cut more rapidly due to higher gradient or more precipitation and succeeds in enlarging the base. Beheaded stream is also called misfit stream.

  • For example, Upper Sittang captured by Irrawaddy in Burma

  • Rapids, cataracts and waterfall – due to unequal resistance of hard and soft rock traversed by river

  • Plunge pool formation

  • Waterfall formation – resistant rock lies transversely, fault line scrap by faulting, water plunges down the edge of plateau and hanging valleys were formed

Image of Waterfall formation

Image of Waterfall Formation

Image of Waterfall formation

Middle (Maturity)

  • Lateral Corrasion increases

  • V shaped valley widens

  • Interlocking spurs

Image result for interlocking spurs

Interlocking Spurs

Image result for interlocking spurs

Depends on flow of volume

Meanders

River cliff (eroding region) and slip off slopes (depositing region)

Image of meander formation

Image of Meander Formation

Image of meander formation

Lower (Old)

Watch video lecture on YouTube: 7 Major Fluvial Depositional Landforms - Carving the Face of The Earth 7 Major Fluvial Depositional Landforms - Carving the Face of the Earth
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  • Lateral corrosion goes on and erodes banks

  • Coarse material drops and fine material carried to mouth of river

  • Flood plains & levees, artificial embankments

  • Braided channels

  • Ox-bow lake or mortlake (dead lake) – also called cutoffs or bayouts in Mississippi basin – degenerate into swamps, becomes marshy and dies

  • Delta – fan shaped and triangular – distributaries

  • Bird foot delta – Mississippi river

  • Arcuate (fan shaped) – Nile, Ganga and Mekong river

  • Estuarine - Amazon, Ob, Vistula river

  • Cuspate (tooth like) – Ebro of Spain

Where deltas are formed?

  • Tideless areas

  • Excessive sediments

  • Shallow region

  • No large lakes

  • No strong currents

River Rejuvenation

  • Being youth again

  • Negative movement when there is upliftment of land or fall in sea level – slope steepens and active down-cutting is renewed

  • Fall in sea level leaves floodplains at increased altitude – terraces are formed and graded profile with rapids or knick points

  • Rejuvenation in upper course leads to steep gorges, in middle course vertical corrasion strengthens (formation of incised meanders – common in River Colorado)

  • Positive movement occurs when there is depression of land or rise in sea level – submerge land along the coast and weaken the eroding power

Human Aspects

  • Chief highways of commerce

  • Navigable (Amazon is greatest navigable river of world), Nile, Mississippi, St. Lawrence, Rhine, Danube, Murray, Mekong, Irrawaddy

  • Delta areas are not good for ports

  • Stagnant water leads to water borne diseases

  • Site for hydro-electric power

  • Construction of dams

  • Irrigation canals

  • Flood plains are richest agricultural areas of world

  • Ganga (jute production), Nile (cotton) – support ports like New Orleans for Mississippi River, Rotterdam for Rhineland & Calcutta for Indo-Gangetic plain

  • Fresh water fishing

  • Political boundaries – Mekong separates Laos and Thailand; Yalu between North Korea and USSR