♥ Monday, April 27, 2009 ♥

Hello I'm being responsible and blogging today! (like right after today's lesson)
Haha hooray me, and for us! :D

So firstly, we learnt about THE RIVER PROCESSES today. :)
Basically, deposition-> transportation -> erosion.
Which means that, after deposition, if there is still excess energy, transportation will take place, and again, if there is still some more excess energy, erosion will take place.
Now, let me show you a graph, which would help to enhance your understanding! ;)

Critical erosion velocity (the Hjulstrom curve)

Okay, I hope that you've understand the first part of today's lesson.
Next, we went deeper into the transportation process!

Traction- Heaviest/Largest material is rolled along the river bed, and this requires the most energy out of all the subgroups.
Saltation- Sand-sized particles bounce along the riverbed in a "leap-frog" motion.
Suspension- Smaller particles (silt and clay-sized) are carried within the water by turbulent flow. Turbulent flow refers to water not flowing straight. :)
Solution- Some minerals will be dissolved in the water and will be carried in the solution, and this requires the least energy.

Now moving on, if there is still excess energy, erosion will take place.

There are 4 types of erosion:
1) Corrasion
2) Hydraulic Action
3) Solution
4) Attrition

Corrasion, or also known as Abrasion, targets the bedrock. The nature of corrasion is either called the 'drilling' or 'sand paper', which is the rubbing effect on sediments. The outcome of this process are potholes banks, which are wider and also smoother because of the 'sand paper effect'.

Hydraulic Action, or also known as Weathering, targets cracks. The nature of this process is air pressure. Air pressure increases when water seeps into the cracks, and air pressure decreases in the cracks when the water flows out. This will cause the cracks to expand, and it is an explosive process. The outcome of this process are collapsed banks.

Solution, targets the bedrock too. Bedrocks are rocks which have not been weathered yet. And the nature of this process is chemically driven.

Attrition, targets the sediment load. And this process takes place because of the impact of the sediment load constantly knocking against each other. The outcome of this process is the formation of smaller and rounder rocks.

Its the end! Haha yay aren't you glad, thats all! (for the erosion process) ;D

Now imagine a hill...
Okay nevermind, I shall attempt to draw it out for you on paint! :/

There you go! HAHA :)

Now to explain about the River Valley...

Upper Course takes the shape of a V-shaped valley due to mass movements, such as landslides and avalaunches. This is called vertical erosion, which deepens the bedrock channel, thus forming landforms like the Grand Canyon.

This beautiful picture shows the famous Grand Canyon of Yellowstone. The V-shaped valley is very obvious in here. :)

Middle Course takes the shape of a wider and flatter valley as a result of the sediments being already weathered, and broken down. This can also be named as alluvial. There is increased sinuosity, which means the distances widens and increases, which forms landforms like meanders and grasslands.

This picture shows a typical meander along the grassland. Notice that the grassland is much flatter and wider than the valley along the upper course. :)

Lower Course also takes the shape of a wider and flatter valley. The reason to this formation is exactly the same as how the middle course forms a wide and flat valley. At the lower course, floodplains and levees are the types of landforms formed.

The picture shows a floodplain, which is flat or nearly flat, and is adjacent to a stream or river. This position causes it to be flooded occasionally. :)

Hope you enjoyed reading this post!

Haha alright, see you people around.

By, Joel Tay (22)

Crapped at 7:39 AM - 3 comments

♥ Sunday, April 19, 2009 ♥

Sorry o3, totally forgot about this!

I'll be referring to the handout.

Page 230: Diagrams

If the shape of the drainage basin is as in the diagrams, then the gauging station is located at the bottom edge of the basin, in order to gauge the entire basin (if it was located at the middle, it would only gauge part of the drainage basin).

Hydrograph of Diagram 1:
-Short lag time
The highest discharge is at the bottom of the basin, due to the wider area and the large amount of tributaries.
Thus, the highest amount of discharge is within the "early" time zone (that is, it reaches the gauging station earlier), leading to an early peak.

Hydrograph of Diagram 2:
-Long lag time
The highest discharge is at the top of the basin, as there is a larger area at the top, so it collects more rainwater.
Thus, the highest amount of discharge is within the "late" time zone (that is, it reaches the gauguing station later), leading to a late peak.

Hydrograph of Diagram 3:
-Double lag time
There are two areas with the highest discharge, one at the top and one at the bottom of the basin, due to the wider areas here.
This leads to a double-peak as the two main discharges reach the gauging station at two different times.

Soil and water:
Base flow comes below the soil
Throughflow comes through the soil
Overflow comes above the soil

Ground water is below the soil and acts like a store of water (it is just above a rock layer), which is a long-term store (as opposed to surface water bodies) and can last for millennia. It is the source of water for wells. It is due to the fact that some rocks are quite porous and can "hold" water after it comes down through percolation, which comes after infiltration.

Throughflow is a less consistent store of water, as opposed to ground water, and it is faster than baseflow. It occurs through infiltration of water through the soil.

Baseflow is slower than throughflow, but it is more consistent than it, since it draws from ground water stores.

The drainage density of a basin is related to the efficiency of the flowing of water (or something like that). The higher the density, the more efficient the flow of water is, leading to a shorter lag time, and vice versa.

A bit on Pg 230, regarding the shape of the basin:
Long basin
-Consistent amount of water
-Early and late time zones both produce the same amount of water.
-Thus, there is an extended peak, as the water does not come all at once.

Round basin
-The discharge reaches the gauging station at around the same time.
-This leads to a short but sharp peak.

Calvin

Crapped at 6:12 PM - 0 comments

♥ Wednesday, April 8, 2009 ♥

Firstly I would like the emphasize that in this post, I would not post pictures/excerpts from our geog textbook as I think it is redundant to do so since it isn't that hard to refer to your geog textbook.

To start things off:

Mr Faizal was once again explaining to us about the water balance because we were unsure about it. This time, he drew a diagram so I took it down...note that not all aspects of the water balance are illustrated here.

Storm Hydrograph:

(enlarge the photo to have a closer view)

This one caused quite abit of a stir...

Lag time: When a rain drop falls, the water level of a river does not shoot up immediately due to drainage. A rain drop still has to go through various processes occur before the water reaches the river. An example would be...imagine that you are a raindrop( so fun! ) and you precipitated down to earth. You land on the soil and infiltrate it. Thereafter, you would percolate and via throughflow, you reach the river. Hence, from this you can see, time was needed for the water to reach the river. This is lag time. Something to take note, a drainage basin with a steeper profile has less lag time and a drainage basin with a gentler profile has a longer lag time due to the speed at which the water reaches the river.
Rising Limb: After some time, water from the drainage basin would arrive at the river and it's water level thus rises.
Max. Capacity: When the river reaches it's maximum capacity and water is still flowing towards it, the river overflows its banks.
Recession Limb: When it stops raining(precipitating) some water within the drainage basin which hasn't reached the river continues its journey to the river. After which, the water level of the river slowly recedes and this is reason for the recession limb.
Rainfall Chart: The graph of the rainfall.

Yayy hope you understood it xD

Done by.. me. (:

Chunwai.

Crapped at 5:29 AM - 0 comments

08IP03! (:

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