breakdown of erosion and deposition

As you have learned from both rivers and coastal, there are 2 main factors that affect all of them: Erosion and deposition. You must take note that erosion is never completely without deposition happening and likewise deposition does not happen without erosion happening.

So in order to help you understand better, I have created this matrix for you all to see:

As you can see here on the outer bend of the meander, you can see that the water volume is bigger than that of the inner bank, so if you are standing on the inner bank, you will not get swept away, but you will at the out bank because of the higher speed. The reason for that is the higher volume of water has more kinetic energy, increasing the speed of the water.

Likewise with destructive waves, the gradient of the coast is steep, meaning there is a greater volume of water and where constructive waves are, the gradient is gentle and the water volume is low. If you follow the matrix above, you can see why the waves are constructive or destructive.

Coastal landforms

This is tricky to explain simpler since it is already simplified as much as possible, just remember that all landforms are created by erosion or deposition. Both processes happen at the same time, but one always happens more than the other.

Here are the landforms you need to learn and the parts in the textbooks you have to read up on and the relevant animation. I can improve on the information,but you all will need to feedback to me.

Cliff
Page 142, 2nd paragraph to page 143, 1st paragraph (remember how to draw diagram A to D)
Animation: http://www.curriculumbits.com/prodimages/details/geography/cliffs-and-wave-cut-platforms.html

Headland & bays
Page 144, 2nd paragraph
Animation: http://www.wiley.com/college/strahler/0471480533/animations/ch19_animations/animation2.html

Under headland and bays, remember that soft rock erodes first before hard rock. You will also need to know about refraction, under the animation, right at the end you will see how refraction occurs.

Beaches
Refer to my previous post on waves and the animation to see how beaches are formed.

Spits and tombolos
For spit, page 147, 1st paragraph from 2ns line to the word before "(fig 7.20)"
Remember to draw the 1st and 2nd drawing of how spits are formed. Remember that a spit is formed through the process of longshore drift.

The 3rd picture is for tombolo!

The last paragraph and 3rd picture should be added in if you are explaining tombolo. A tombolo is when a spit meets an island and fuses together. I will get the picture from East Coast Park soon, busy with my kids who just came back from Australia! =p

Here is the animation for a spit:
http://whs.moodledo.co.uk/file.php/1365/Coastal%20Systems/Coasts%20baymouth%20bars%20pits.swf

Longshore drift

Study and burn into your head page 139 of your textbook 2nd paragraph under transportation.

Here is an animation for you to study:
http://whs.moodledo.co.uk/file.php/1365/Coastal%20Systems/Longshore%20%28Beach%29%20Drift.swf

Please remember to know how to draw the diagram as seen in page 139!!

Coastal-Waves

Waves are formed by wind energy, the greater the surface area (fetch) the wind is blowing, more energy is transferred.

Constructive waves, notice how gentle the gradient is? This increases deposition.

Destructive waves, notice how steep the gradient is? This leads to more erosion, as the waves lashes out at the cliff.

2 types of waves= constructive and destructive

Constructive waves:
Swash=strong
Backwash=weak
Gradient=gentle
Energy=low
Process=more depositional


Destructive waves:
Swash=weak
Backwash=strong
Gradient=steep
Energy=high
Process=more erosional

Here is an animation for the effect on the beach by constructive and destructive waves: http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/0072402466/30425/14_08.swf::Fig.%2014.8%20-%20Seasonal%20Cycle%20of%20a%20Beach

River management in very short form!

Channelisation: Re-alignment and resectioning

Realignment:
Purpose=straightening of the river
Pros=to increase water speed, remove sediments faster and reduce flooding
Cons=Expensive and high manpower, destroy natural environment
Example=Singapore River

Resectioning:
Purpose=widening and deepening of the river
Pros=to hold more water, increase water speed, remove sediments faster and reduce flooding
Cons=Expensive and high manpower, destroy natural environment
Example=Singapore River
_____________________________________________________________________

Bank Protection: Planting vegetation (soft engineering) & building dykes, revetments and gabions (hard engineering)

Planting vegetation:
Purpose=plant plants along river banks
pros=cheap and roots help to prevent soil erosion.
Cons= Slower water speed
Example= Kallang River

Building dykes, revetments and gabions:
In case you are not sure what is the difference, dykes are simply rocks, sand or concrete walls. Gabions are small rocks in wire cages, and revetments are rocks cemented together.
Purpose= Artificial man made bank walls.
pros=long lasting, faster water flow due to less friction
cons=expensive and high manpower
example=Kallang River

River landforms

waterfall
description - A steep drop in the bed of a river causing the water in the river to fall vertically.
explanation - Waterfalls occur where a band of harder rock crosses the path of a river. The river is less able to erode this harder rock and leaves it as a step in the river's long profile.

Here is an animation link for waterfall formation: http://whs.moodledo.co.uk/file.php/1365/Fluvial%20systems/Waterfall2.swf

ox - bow lake
description - This is a truncated (cut off) section of a meander in the river channel which forms a 'c' shape.
explanation - This is formed by the loops in a meander eroding the flood plain until eventually the loop in the meander is left cut off from the main river channel.
diagram - Diagram 2.6h shows four stages in the formation of an ox - bow lake.

.

meanders
description - These are bends (loops) in the river. explanation - Lateral (sideways) erosion of the river channel results in the river forming a winding pattern. (tip ! if a river or stream has an absolutely straight pattern then it is probably artificial i.e. a canal).
diagram - As the water flows down a river, its speed is faster on the outside of the meander causing erosion and slower on the inside of the meander resulting in deposition.
This is shown in the diagram below. Mark two areas of erosion and two areas of deposition on Diagram 2.6i.

here is an animation for meander and ox bow lake: http://www.cleo.net.uk/resources/displayframe.php?src=309/consultants_resources%2F_files%2Fmeander4.swf

flood plain
description - This is an area of flat land found on either side of a river. This usually becomes wider as the river nears its mouth.
explanation - The flood plain is the area of land which is flooded when a river overflows its banks. In this area layers of alluvium are laid down. The soils are thus thick and fertile and the land is flat.

Here is an animation for floodplains:
http://whs.moodledo.co.uk/file.php/1365/Fluvial%20systems/Features%20of%20a%20River%20Floodplain.swf

here is an animation link for levees:
http://www.geography.ndo.co.uk/animations2.htm

levees
description - These are mounds of alluvium piled up along the river's edge.
explanation - These are formed by the river depositing the coursest part of its load (pebbles, gravel and sand) close to the river channel when the river floods. This happens because usually when the water overflows the river bank its speed (and therefore its ability to transport alluvium) is greatly reduced.
Sometimes these are built by people in an attempt to prevent the river flooding.
Why should people go to so much trouble and expense to prevent a river flooding ?
diagram - Examine and suitably shade in the following diagram.
Colour in yellow the levees on Diagram 2.6e

v-shaped valley
description - This is a valley whose typical cross section is shaped like a 'v'.
explanation - As the river cuts down into the landscape in an upland area, gravity and mass movements roll material down the valley sides to give the valley a typical 'v' shape.

REMEMBER: All landforms are created by erosion and deposition, it is only a question which process comes more into play, for example:
Valley, waterfall, Gorge = More erosion
Meander=both erosion and deposition
Floodplains, levees, ox bow lake, deltas=more deposition

Deposition (Rivers)

For Deposition, this are the factors that will lead to increase in deposition:
1. Low rainfall.
2. lower gradient (lower course of the river, less gravity pull)
3. increase in load (more rocks, more energy used up)
4. Increase in friction (such as rocks and plants in the way)

Follow this 4 points to help you understand the summary matrix in your textbook on page 117.

Check this animation for a better clarification:
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0604/es0604page01.cfm?chapter_no=visualization

Transportation (Rivers)

Remember S.S.S.T. (pronounced as sit)


Nuff said, picture says everything.

Erosion (rivers)

Remember C.A.S.H.

Corrasion (abrasion) = rocks scraping the river bed or banks.
Attrition=rocks suspended in the water
Solution=rocks dissolved by weak acidity in the river water.
Hydraulic Action=Fast moving water dislodge rocks.

Check page 115 of your textbook for the summary matrix at the bottom for reference.

Here is a animation link for you all to see:
http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/accounts/staff/rchambers/GeoBytes%20GCSE%20Blog%20Resources/Animations/rivererosion_njenkins.swf

Extra Notes from the internet:

Here is a set of notes from other schools, ours is inside too, this set of notes look really good:

http://www.slideshare.net/Chiamdj/physical-geography-chapter-3-rivers-and-coasts

River Energy!

There are 2 main factors for river energy: Velocity & Volume.

Velocity is caused by the following factors:
Slope gradient: Gentler the slope, the slower the flow. (caused by gravity)
Channel roughness: Rougher the channel, the slower the flow. (caused by friction)
Wetter perimeter: Bigger surface area, the slower the flow. (big area=more friction)

Volume is caused by the following factors:
Drainage Basin size: Bigger basin, more water.
Presence of vegetation: less plants, more water. (plants take more water plus they increase interception of rain leading to higher infiltration, here is a picture below to help you understand: imagine the tree acts likes a speed brake, when the water slows down, it is easier for the water to enter (infiltrate) the ground as the ground cannot absorb as fast as the volume of water coming down.)




















Rock Permeability: Less porous, more water. (think of a dense sponge)
Climate: More rain, more water.

Here is a mind map for river energy for your reference: