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1. WORKS OF RIVERS, WIND
AND SEA AND THEIR ENGINEERING
IMPORTANCE
Lesson7
Baculo, Ashley,
Baliwag, AubreyBinondo,
Binondo, Zara Veronica C.
Canono, Ryan

2. RIVERS
■ As the rivers have a beginning which is called head. The place where as river ends in
the sea or lake is called mouth. In all the cases, the slope of the rivers at the head is
high so that it can carry all the materials (the coarse and fine weathered products)
from the parent rocks down.
■ The slope slowly decreases and in the plains it is smaller. Thus the shape of the
slope from the head to the mouth is concave (facing the sky)

4. PLAYFAIR’S LAW
(FUNCTION OF A RIVER)
John Playfair

5. WHO IS JOHN
PLAYFAIR?
• Scottish Geologist and mathematician
• March 20, 1748, Benvie, Forfarshire,
Scot.
• Died July 20 1819, Burntisland, Fife
• Explanation and expansion of ideas on
uniformitarianism.
• He was the first to propose that a river
cuts its own valley and was also the first
to recognize the transport role of glaciers.

6. PLAYFAIR’S LAW
(FUNCTION OF A
RIVER)
• This law indicates how deep valleys
and landforms have been formed.
• These landforms have been formed by
the three geologic functions of the
rivers:

7. GEOLOGIC FUNCTIONS OF THE RIVERS
EROSION
TRANSPORTATION
DEPOSITION

8. EROSION
■ The erosion is one of the most expressivefeatures of river which is turbulent with
currents in all directions. Most rivers carve the river valley by erosion.
■ The river erodes in four main ways:
1. Attrition
2. Corrosion
3. Corrasion
4. Hydraulic action

9. HYDRAULIIC ACTION
■ The waves crash against rock and compress the air in the cracks.
■ This is the force of the water of the fast flowing rivers that can dislodgematerials
from the river banks and river beds.

10. CORRASION (ABRASION)
■ Eroded particles in the water scrape and against the rock (cliff), removing small
pieces.
■ This is the abrasive force producing a mechanical erosion of rocks by the sediments
the river carries.

11. ABRASION: THREE FACTORS
■ If the transported materials is hard in relation to the bed, the bed gets affected and
wears down.
■ If both are hard then the bed gets polished
■ If the bed is harder the bed is not affected.

12. ATTRITION
■ Eroded particles in the water ash into each other and break into
smaller pieces. Their edges gets rounded off as they bash into each
other.
■ This is due to the rubbing of the particles being carried by the river
when they are thrown at each other.

14. CORROSION (SOLUTION)
■ In this process the water dissolves particles of the river
banks or bottom and carries them in solution.
■ Weak carbonic acid in sweater dissolves rock like chalk and
limestone.

15. TRANSPORTATION OF
ERODED MATERIALS

16. TRANSPORTATION OF ERODED
MATERIALS
■ The materials that have been eroded have to be transported down the river. There
are ways in which the river can transport the materials dislodged by it.
1. Dissolved Load
2. Suspended load: the fine particles of Sand silt and clay can remain in suspension.
3. Bed Load: The large-sized materials settle to the bed of the river and move along
the bed by rolling, sliding or by sudden movement (saltation). This bottom load is
also called the traction load.

17. DEPOSITION (ALLUVIAL DEPOSITION)
■ When the velocity of water in river is not enough to carry the load of soil particles it
has been carrying, it deposits the load at the places of low velocity. This usually
happens in the regions where the slope of the river bed becomes gentle.
■ These Function act on the following three physical processesinvolved in the
formation of river valleys, namely:
1. Deepening of the river valley
2. Lengtheningor shorteningof the river valley
3. Wideningthe river valleys

18. CARRIED OR DEPOSITED PARTICLES BY
RIVER WATER
■ Different particles of soil require different velocities.
1. For them to be sourced by water
2. For them to be carried in water
3. To be deposited on their path.

19. Figure 10. Fields
of erosion,
transportation
and deposition
of
river sediments
in the flow of
rivers.

20. STREAM CYCLE

21. Juvenile or Youth Stage (Upper Course)
■ This is the stage of high downwardvertical erosion. It develops the following
characteristic formations:
a) V- shaped valleys
b) Gorges and canyons
c) Rapids and cataracts (Rapids of greater dimensions are knownas cataracts)
d) Waterfalls
e) Holes
f)Piracy (Capturing of a streamlet that flowed into one river another stream that
flows into another river)

22. ■ EXAMPLE:

23. Maturity Stage (Middle Course)
■ This is the middle course of a river where the gradient is gentler and the river valley
becomes wide, leading to the following features:
a) Meanders
b) Flood plain

24. Meanders
■ The term meanderis derived from river Meanderz in Turkey, which flows in loops.
■ In the wide plains the river may be made to bend and take a curve due to some
obstructions.
■ Then the velocity around the outside bend becomes very much higher and hence
the river cuts down the river bank.
■ As the velocity inside the bend being less, deposition of fine particles takes place
which is shown.
■ The clay deposits are found more on the inside of the river bends where the velocity
is low.
■ As erosion cuts away bank on one side and deposition takes place on the opposite
side, the river migrates laterally and produces a meandering river

25. EXAMPLE:

26. Flood plain
■ The flood plains occur in the middle course of the river that has formed its maturity.
The valley characteristics are absent and the river flows along a wide and flatter
region. Overflow of the banks and flooding happens during floods. This leaves
behind deposits of silt on both sides. These are called flood plains

27. EXAMPLE:

28. The following are the geomorphologic features of this region:
Levees- : The natural embankments formed by the river in the flood plains are called
levees. As the floodwater in the river spills on the flood plains it loses energy and coarse
materials are depositedat the edges. Over the years raised edges are formed which are
called levee
Oxbow lakes- The meanderingriver can cut across the flood plain and form the oxbow
lakes. The oxbow lakes can develop into swamps in course of time.
Braiding- When the river reaches the end of the middle course the river deposits more
and more of the load it has been carrying and may break up into a network of
interconnected channels resembling the strand of a braid. This happens more often
towards the beginning of the old stage of the river.

29. ■ EXAMPLE:

30. OLD AGE (Lower Course)
■ In the last stages of the river just before it joins the sea or lake, the flow becomes
gentle as the slope of the river in considerably reduced. If it joins the sea, there are
waves, sea currents and also change in the salinity of water. The suspended
material is deposited. If the amount of material is not large then it will be carried
away by the sea by its currents and waves. This is what happens to the small rivers
on the west coast of peninsular India. However if the rivers are large like those which
flow into the Bay of Bengal and the amount of suspended materials carried by river
is very large, a large amount of the suspended materials will be deposited at the
mouth of the river to form deltas.

31. - Delta-Building:
■ The subject of delta-buildingis very interesting and can be explained as follows. The
deposition of material at the mouth of the river and into the sea materially increases
the length of the river. This decreases the slope and hence more deposition
happens. For example, if the slope was 2 ft in 90 miles and if the length of
deposition of sediments of the river is increased to 100 miles, the slope reduces
from 1 in 45 to 1 in 50. The velocity of water decreases and more deposition takes
place. Also during the floods because of the raising of the beds, the river will have to
branch off before it falls into the sea to increase the flow and thus form the typical
delta.There are many types of deltas of whichthree are the typical.

32. EXAMPLE

33. 1) Arcuate deltas
■ : It looks like those of the river Ganges and Nile.

34. EXAMPLE:

35. 2) Birds foot deltas
■ It appears like that of the Mississippi river. These rivers carry extremely fine particles
and clays. The deposits do not allow much flow under the surface (the deposits
being clayey or impervious), so that the flow of water is concentrated in a few large
channels which form a pattern of the bird’s foot. Thus this type of deltas has clay
deposits.

36. ■ EXAMPLE:

37. 3) Estuarine filling:
■ As in the Hudson River which flows into an estuary and where the deposits are built
in the form of long bars at the mouth of the river. The forms extensive filling of soil
bars or marshes.

39. ■ The rivers that fall into lakes will also build deltas. The deltas, built in
lakes and in land seas or bays, are more perfect than those built in
the open ocean with strong currents and waves. The deltas built in the
seas will be usually irregular.
■ The three stages or courses do not depend on the age of the river but
on the present performance of the river at a given place which
depends on many present factors. It is also interesting to consider the
two basic physiographic concepts in river flow that of (a) base level
and (b) profile of equilibrium which varies with the flow.

40. a) Base Level
■ : This is the level that controls the depth of the stream erosion. No stream base level
can be below the sea level.
■ . A base level is the depth limit of the valley and is controlledby the water level in the
body of water into which it flows down (ocean, sea, lakes, etc.).

42. b) Profile of equilibrium
■ : A stream is said to have reached its grade or profile of equilibrium when its slope
and volume of water it carries are in equilibrium with the sediment load it
transports.
■ The annual and seasonal fluctuations in volume and velocity bring about continual
readjustments of their profile.
■ The gradient is expressed as slope of the profile of equilibrium at the steady state of
flow of the river with no erosion or deposition. It is expressed in meters per
kilometer, meter or feet per mile.

43. ■ No implication of years is to be read into the
terms juvenile, youth and old stages. It only
represents the various stages of development
of the river. Thus a youthful stream in hard
rock, high above the base level (profile of
equilibrium) may be millions of year of age,
whereas the old stream near the base level
may be only a few thousand years of age.

44. REJUVENATION OF RIVERS
■ As already indicated, youth and old age does not denote the age of the river but only
whether it is eroding (juvenile) or is in equilibrium or in depositing (old age) at
present. Thus if a mature river has its gradient increased for example, by lowering
the sea level or some construction then the river will work to reduce the gradient by
cutting down the previously deposited flood plain until the former gradient is again
established. This is in accordance with the Playfair’s law.

45. CORIOLIS EFFECT AND FERREL’S LAW
■ The effect which causes the deflection of a body in motion on earth due to the
rotation of the earth is called the Coriolis Effect. Accordingto Ferrel’s law, due to this
effect if a body moves in any direction on the earth’s surface, the deflection force
will act to the right in the northern hemisphere and the left in the southern
hemisphere.
■ According to this law a river flowing in the north direction in northern hemisphere
tends to erode the east banks more than the west banks. Similarly a river in the
northern hemisphere flowing in south direction tends to deflect to the west; land
erosion will take place more of the west banks than the east banks. However in all
the cases the resistance of the material to erosion and slope of the land will also
play a prominent part.

46. WIND
■ The movementof air over the surface of the earth is called wind.
■ Wind performs all the three functions of erosion, transportation and deposition of
the weatheredproducts.
■ The wind deposits are also called Aeolian deposits.

47. EROSION WORK OF WINDS
■ The processesof erosion due to wind are (1) Deflation, and (2) Abrasion

48. 1. Deflation
■ The act of removing the loose particles of the earth from one area and forming
depression as shown in the figure is called deflation. By this process of removing the
sand to the groundwaterlevel, oasis is formed in deserts.

49. Abrasion
■ Abrasion is the process of impact of the coarse particles in the wind against
formations like understanding rock and erodingthem. Most of the coarse materials
in the wind remain in the lower 30 to 60 cm height of the wind from the ground as
bed load and some coarse sand particles will be swept by rolling them on the
ground. Hence the rock erosion produces profiles of upstanding rocks as shown in
figure. In such cases there will be more erosion at the lower level and very much
less erosion at the higher level of the upstanding rocks.

50. SAND STORMS AND DUST STORMS
While the lower part of the wind consists of sand, the upper part is mainly the fine
particles of dust. Thus the lower part produces the sand storms and the upper part
produces dust storms.
SAND STORMS describean exceptionally strong wind, which picks up and carries
a large amount of sand in the atmosphere. They can reach up to weight of 10-50 ft.
DUST STORMS carry much smaller particles, whichcan be carried higher and
further tyan sand storms.

51. DEPOSITION OF SEDIMENTS
The velocity of the wind carrying the particles may get reduced by some
obstructions like hills, mountains,forests sudden changeof climate presense of water
bodies like rivers, sea, fall of rains, etc. This reduction of velocity forces deposition of
the particles the wind is carrying, and they form typical Aeolian deposits.
TWO (2) IMPORTANTSTYPES OF DEPOSITS:
• Sand Dunes
• Loess

52. SAND AND DUNES
•The sand dunes are formed by deposition of sand carried by winds. It is heap of sand
conical in cross section with a gentle slope on the windward side and a steeper slope on
the leeward side.
•There is much type of formations such as the (1) LONGITUDINAL DUNES, (2)
TRANSVERSE DUNES and the most common(3) CRESCENT SHAPE DUNE called
BARCHANS.
• The dunes may get stabilized as “ fixed dunes “ in one place or like the barchans
move on the directions of the winds.
• Sand dunes can be formed at three (3) kinds of locations namely:
1. Near sea shores as shore dunes
2. Bed of rivers as riverbed dunes
3. Inland as desert dunes

53. PLAN VIEWOF SAND DUNES
(a) Crescent Shaped Dune called Barchans
(b) TransverseDune
(c) Longitudinal Dune
SEIFS are also called LONGITUDINAL DUNES.
Theyare formed parallel to the directions of the
wind as shown in the figure. These are usually
found in the places where steadywind prevails.
These dunes may exist in great heights and up to
200 m along long distances.

54. LOESS DEPOSITS
•The term loess was first applied to the loose unconsolidated deposits found along the
Rhine River extending to the Black Sea.
•Loess is fine particles usually derived from flood plains and glacial outwash laid by
the wind. It consist of the loosely arranged angular grains of calcareous silt, rich in
quartz with calcium carbonate.
• It is the uniform size and compositionformed without stratification.
• The loess deposits pose two (2) engineering problems:
1. The collapese of its structure on wetting or saturation.
2. Because of its losse structure, they are subject to frost heaving in cold countries,
when they occur on highway layouts.

55. SEA- Seas and Oceans covered 70% of the Earth’s surface. The term “ sea “ is generally
used for saline water bodies surrounded by landforms and also water bodies of
shallowerdepth less than 4km.
FORMA
TIONOF THE SHORELINE
1.sea waves, sea currents, the theory of formation of coastlines by erosion, deposition
and sea levelchanges.
2. Coral deposits
SEA WAVES -The waves are created by the winds. This disturbance travels to the coast
and gets its energy destroyed.The distance between the crests of adjacent waves is the
wavelength in the deep part of the sea; waves are only oscillatory (goes only up and
down). These are called oscillatory waves.

56. LITTORAL CURRENTS - The word littoral means pertaining to the shoreline. The
movement of water up to the coast when the waves break is called swash and the
return of the water back into the sea is called backwash.While the flow (velocity) of the
swash is directed to the shore the currents set up by the backwash(which is called the
rip current) usually act below the sea level and are directed to the deeper waters.
WAVES AND CURRENTS
(1) Ordinary Waves
(2) Transitory Waves
(3) Littoral Currents
(4) Rip Currents

57. FORMATIONOFCOASTLINEBYMARINEEROSIONOF
COASTALROCKS
Four distinct processes.
1. Abrasion: Waves hurl pebbles, sand boulders and other substances
against base of cliffs, under-cutting the base of cliffs on the sea
coast.
2. Hydraulic action: The cracks in the cliffs are filled with sea water from
the waves and its sudden release during the retreat of the waves
cause the material around the cracks to break up.
3. Attrition due to rubbing together of particles in the waves and get
broken up.
4. Solution (Corrosion): By chemical action leading to solution of some
of the constituents

58. LANDFORM FORMEDBYMARINEEROSIONOFROCKS
ON SEA
COASTS
Landforms are created by the above erosion of the rocks beside the sea.
■ Sea Cliffs

59. Landforms are created by the above erosion of the rocks beside the sea.
■ Sea caves, Arches, stacks and stumps
LANDFORM FORMEDBYMARINEEROSIONOFROCKS
ON SEA
COASTS

60. ■ Wave-cut platforms
LANDFORM FORMEDBYMARINEEROSIONOFROCKS
ON SEA
COASTS

61. FORMATIONOFLANDFORMSBYCOASTALDEPOSITION
■ the sediments entering the sea are carried away by the sea waves and deposited in
the sea or alternately it may be taken to the other parts of the seacoast.
■ deposits on the coast forms the landforms called 1.) beaches, 2.) spits and 3.) bars.
1. Beaches: These are formed by the deposition of sand and gravel along the coast. In
theory, beach is the zone extending from low water sea level to the upper limit of
high water.
2. Spits: Spit is a long and narrow extension of the beach into the sea. They are sand
deposits formed by shore drifts.

62. FORMATIONOFLANDFORMSBYCOASTALDEPOSITION
3. Bars: Bars are long deposits of sand formed in the sea parallel to the
shoreline. This may be above or below the sea level. Those above the sea
level are called barrier beach.
Tombolo: If the bar forms a link to
the mainland the link is known as a
tombolo
Lagoon: A bar spit can enclose a
portion of the sea

63. FORMA
TION OFLANFORMSBYSEALEVELCHANGES
■ A rise in sea level can form a fjord. Fjord is a narrow long valley.
There are called shore lines of submergence.When the sea level
falls and more of the land gets exposed they are known as raised
beaches. The landforms formed by this process are called land or
shores of emergence.

64. Types of Shorelines:
1. Shoreline of submergence - Ashoreline, characterized by bays,
promontories, and other minor features, formed by the dominant
relative submergence of a landmass. Also known as positive
shoreline; submerged shoreline.
2. Shoreline of emergence - A straight or gently curving shoreline formed
by the dominant relative emergence of the floor of an ocean or a lake.
Also known as emerged shoreline; negative shoreline.
FORMA
TION OFLANFORMSBYSEALEVELCHANGES

65. TYPESOFCURRENTSTHATAFFECTTHECOASTLINE
■ Underflow or rip currents and littoral currents
– We noted that the waves that come to the shore with a certain
velocity, after flowing up the slope of the beaches, the water
returns to the sea with a velocity depending on the slope of the
beach along the bottom. This current is called undertoe or rip
current. Already dealt with in the current that moves along the
coast is called littoral current. This current will flow parallel to the
coast until depressions are found which will give an opportunity
for seaward exit.

66. ■ Tidal Currents
– The rise and fall of the tide in an open coast does not produce
much effect on the deposits on the shoreline. However if the tides
are very high and the fall of the tide has to take place through a
narrow exit then the large velocity at the place of exit may have
some effect on the nearby deposits at that place. The high velocity
can lead to erosion.
TYPESOFCURRENTSTHATAFFECTTHECOASTLINE

67. SEAWALLS AND
BULKHEADS

68. SEAWALLS AND BULKHEADS
■ Seawalls and bulkheads are the massive structures built alone the
coast. (Built parallel to the coast.)
■ Their faces may be vertical, sloping or parabolic to produce as little
force on the wall as possible.

70. SEAWALLS AND BULKHEADS
■ Bulkheads are made of steel or concrete or timber piles and they are used where
the impact of waves is not very large. The large hollow prestressed concrete pipes
have been used for shore protection near Chennai harbor with some success.

71. CONSTRUCTION OF REVETMENTS
■ Revetments against the coast are usually built with large stone or
concrete block big enough to resist the force of the waves placed on
each other. It should also be built high enough to prevent overtopping
of the ordinary waves. For economy, the height may be such that
stormwaves may just spill over it.

72. ROCK REVETMENTS
■ In stream restoration, river engineering, and coastal engineering, “revetments” are
sloping structures placed on banks or cliff in such a way as to absorb the energy of
incoming water.
■ Slope angle of layered boulders to absorb, rather than reflect

73. PREVENTION OF SILTING
■ Corals are very small sea organisms that live in very large colonics especially near
the tropics. They secret calcium carbonates and build coral reef. These coral
deposits may be built on sand deposits in the sea.
■ Three types of corals reefs deposited:
1. Fringing reefs
2. Barrier reefs
3. Attols

74. FRINGING REEFS
■ Fringing reefs grow near the coastline around islands and continents. They are
separated from the shore by narrow,shallow lagoons. Fringing reefs are the most
common type of reef that we see.

75. BARRIERREEFS
■ Barrier reefs also parallel the coastline but are separated by deeper,wider lagoons.
At their shallowest point, they can reach the water’s surface forming a “barrier” to
navigation.

76. ATOLLS
■ Sometimes known as a coral atoll, is a ring-shaped coral reef including a coral rim
that encircles lagoon partially or completely. There may be coral island or cays on
the rim.