Today (24/4) Ms Lin walked into class.

and basically covered some new content that was essential to the following lesson's discussion.

Upper Course	Middle Course	Lower Course
V-shaped Valley	Wider flatter valley	Wider flatter valley
Mass movements	Wider and deeper channel Alluvial(loose material like sand/sediments)	Wider and deeper channel Alluvial(loose material like sand/sediments)
Vertical erosion (Bedrock[hard rocks] channel)	Increased sinuosity	Floodplains and levees

THEN we went onto River Processes and sedimental transportation

Ways that sediments can be transported

1. Traction - heaviest material that rolls along river bed requires the most energy to carry

2. Saltation - Rocks bounce 

3. Suspension - Small particles like salt/clay/sand that is carried with water through turbulent flow. The MAIN form of sediment transfer

4. Solution - Minerals dissolved

Processes of erosion

The excess kilojoules of a river is harnessed to erode, the process of picking up and removal of material.

 

	Corrasion/Abrasion	Hydraulic Action	Solution	Attrition
Targets	Bedrock	Cracks	Bedrock	Sediment load
Nature	Drilling/sand paper	Pressure	Chemical	Impact
Outcome	Vertical/lateral erosion	Collapsed bank		Smaller/rounder

Erosion of RIVER CHANNEL

Sandpaper - the sediment load rubs against load, in collision

Hydraulic Action - Water enters the holes/cracks, which results in increased pressure. The air bubbles burst after heavy compression

Attrition - High pressure just result in impaction, collision 

There was this Velocity-Particle grain size(diameter) graph shown which shows the velocity needed to carry a certain coarse material. However, the values of the graph cannot be considered seriously because not all particles are round.

So after these mundane content we started looking at pictures! Such as deltas...meanders...etc. and apply our knowledge!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

taro

Friday 17th April 2009 =D

Today we did a recap on River Processes:
1) Erosion
2) Transportation
3) Deposition

So basically, the river erodes the rocks or soil and transports it and then deposits it when there is not enough energy left to carry it. (details are in the previous post by DL =D )

So we went over to the concept of Energy!

What affects the energy of the river?
- Discharge, which is the amount of water
- Velocity, which is based on the gradient, the cross-section/channel shape, and friction)

Discharge is easy to understand. If the river has more water flowing, it has more energy =D

Gradient too, if the river is more sloped (say, a waterfall, then it has more energy)
This is due to gravity:

Remember this?

Oh the horror...

Now for Channel Shape.
If the channel is narrower, there will be less friction for the water because there is a greater wetted perimeter/ greater amount of water in contact with the perimeter, thus wetting it/ greater- oh i dunno what la...
(wikipedia puts it as 'the greater the wetted perimeter, so there =D )
Also, wetted perimeter = the cross-sectional area that is 'wet' (courtesy of wiki as well xD)

So a river channel like this

will have more friction than one like this


supposedly, but won't the additional water that figure 1 can hold make up for the increase in the wetted perimeter, thus having a canceling effect or something?

ANYWAY, lastly, we have friction =D
This changes with different types of rocks

Next, we split into groups to try and predict how velocity changes from source to mouth.
btw, the source is defined as the tributary that is furthest away from the mouth =D

My group said that it varies because the friction due to greater wetted perimeter cancels out with the greater amount of discharge, so it's mostly dependent on the gradient, which can change randomly =D

The correct answer, anyway, was that velocity increases downstream as the eroded rocks get smaller and rounder, sediment load decreases, so velocity increases downstream =D

KK so that's basically what we did for lesson xD with this final extra question:
Will a group of salmon travelling upstream to, let's say, Bread, affect the velocity of the river?
My answer: No! xD

Here's a diagram why:
oh look, a fish!
Fishie wags his tail...


Fishie moves forward, Pushing the water infront of it infront...

So now we have a swarm of salmon...

AND VIOLA!!! (i'm sure i spelt this wrongly)
THE ARROWS CANCEL EACH OTHER OUT!!!
you can see that there are the same number of front-arrows as back-arrows =D

And this concludes LLJ's FISH THEORY OF CONSTANT VELOCITY

(All pictures courtesy of ME and Macromedia Fireworks xD [seriously, you all should get this])

Current Geo Challenge Score: 1833 (T.T)

Oh well...

Until next time then...

Well-Wishes
LiangJie

MR HEAH GET WELL SOOOOON!!!!!!!!! <3 (hahas yes i just typed that)

07/04/09 Daryl Lee

What a rainy day... Perfect for GEOGRAPHY =D. Today, Mr Faizal showed and explained to us what was happening at the 'garden' below our classroom.

So.. from what we have learnt from Mr Heah,

Firstly, there is interception, which is the trees, the grass and whatever that is obstructing adrop of water from falling down to earth to get absorbed by the soil.
SOMETHING LIKE...
YES! That is interception.

Then, there is infiltration, when water infiltrates in the soil.
When the soil reaches infiltration capacity, overland flow might result like we saw from the top of our classroom. Overland flow sometimes results in floods when it gets too serious. That is why vegetation plays an important role in preventing the soil from clumping together to increase infiltration capacity.
<---- OVERLAND FLOW There is also throughflow, which is water moving through the soil.
It is not as fast as overland flow, travelling at between 0.005 and 0.3m per hour.

After through flow, there is an even slower kind of flow, which is groundwater flow.
This happens when the underlying bedrock is permeable. Water will then slowly soak up the soil below and it will then flow through the small pores of rocks. This process is extremely slow. (takes a few THOUSAND YEARS)

Also, Mr Faizul also stated that some parts of the soil had clumped together as there is no vegetation on it and water is unable to infiltrate there. Therefore, we could see more overland flow at those parts of the 'garden' then at the parts with vegetation on it.
Human activity has also affected the hydrological cycle as water is unable to infiltrate through concrete and hence we could see (from the side of our classroom) lots of overland flow.

That's not all, we also read on the river channel processes which i will type about now =D.

Firstly, there are three river processes:
1) Transportation
2) Deposition
3) Erosion

1) Transportation
before we can talk about this, we have to know the kinds of load that a river carries
i) Dissolved load- Transport of chemicals in water (Solution)
ii) Suspended load- Sediments that is being carried by the flow of water (Suspension)
iii) Bedload- Material that is too heavey to be suspended in the water.
--> These are transported by rolling (traction) or bouncing (saltation)

so much sediments!

2) Deposition
Happens when velocity begins to fall, it has less energy and can no longer hold the load it is carrying.
Occurs when,
1) The load suddenly increases
2) Shallow waters
3) Low precipitation
4) When a river enters a sea or a lake (less velocity)
5) River overflow its bank hence the velocity outside the channel is reduced

3) Erosion
It is the picking up and removal of material.
3 types:
i) Corrasion- particles picked up by the river is rubbed along the river beds, wearing them away
ii) Hydraulic Action- occurs mostly at waterfalls and rapids. Air bubbles may burst in these areas sending out shockwaves which may increase erosion, this is called cavitation
iii) Solution- Dissolved CO2 from the air which is dissolved in the water may react with limestone and chalk, causing them to dissolve.

Lastly, there is attrition which is the particles that are being transported by a down-river crashing against one another causing them to become increasingly rounder and smaller in size.

ALRIGHT DONE! =D
GET WELL SOON MR HEAH =D

GET WELL SOON MR HEAH

WE MISS YOU!!! PLEASE PLEASE PLEASE GET WEEL SOOON!!!!! YOU ARE THE AAWESOME-EST TEACHER EVER! LIKE SERIOUSLY. WE ARE ALL ROOTING FOR YOU TO GET BETTER. WE NEED YOU FOR GEOG!!!

love,

Nurul

HEY MR HEAH! GET WELL SOON!!! YOU ARE THE BEST TEACHER EVER, WITH YOUR ABILITY TO EXPLAIN CONCEPTS THOROUGHLY AND EFFICIENTLY! ABOVE ALL THAT, YOU'VE BEEN A REALLY FUN TEACHER TO HAVE! I FEEL THAT IT IS FAIR TO SAY THE WHOLE OF 01 REALLY ENJOYED YOUR LESSONS, OUTDOOR AND INDOOR, AND WE REALLY WISH TO HAVE YOU BACK FULLY RECOVERED!
GO MR HEAH!! HEEEEALLLL! o8IP01 WISHES YOU ALL THE BEST!!

-
GET WELL SOON MR HEAH! :D :D :D :D
we all missed you and your fun lessons!

GET WELL SOON MR HEAH!!!!=DD
[place your wishes here]

Jude Dominic

Yesterday's lesson was mainly about hydrographs. A hydrograph shows the discharge of a river over a period of time. Storm hydrographs show the river's response to rainfall events. This is an example of a hydrograph:

The x-axis shows the precipitation as well as runoff discharge, which is measured in cumecs(cubic metres per second) and the y-axis shows time in hours. The green bars refer to the amount of rainfall. The curve shows the discharge through storm flow(throughflow, overland flow etc.), which is indicated by the blue part of the curve, and baseflow, which is indicated by the red part of the curve. The lag time is the time between the peak rainfall and peak discharge. The curve can vary due to different factors. If there is very heavy rain and the soil is saturated or frozen, there will be heavy overland flow and the curve will be very steep. However, if rain is light and there are a lot of trees and other vegetation( which results in more interception and obstructs overland flow), the curve will be less steep.

Hydrographs are highly useful to people managing drainage basins. The discharge rate of a river can sometimes be so high that the river floods its banks. Follow this link to see an animation of a flood(go to the bottom of the page and play the animation): http://www.geology.sdsu.edu/classes/geol351/hydrographs.htm. Human activities can also change a hydrograph. For example, there will be a generally low discharge rate in an area with much vegetation. However, if people clear the vegetation to gain land for other purposes, the discharge rate will become higher and flooding may occur.

We were asked to do the questions on page 231 of our notes as homework, so I may as well post up the answers here(although I'm not sure if they're correct. And I'm not going to give you the hydrographs here, because I can't draw hydrographs well on my pc).

2a) Lag time is the amount of time between peak rainfall and peak discharge.

2b) If lag time is short, a large amount of water will flow out in a short time, so there is a greater chance of flooding. If it is long, the water will drain out at a lower rate and there is a reduced risk of flooding.

3(i) a small drainage basin with very steep slopes: I won't give the graph but will describe it. The curve is a very steep one with a short lag time as the discharge rate is very high because of a steep slope.

3(ii) a linear shaped drainage basin: This graph has a gentle curve and long lag time. This is because the water discharges out slower due to the absence of a slope.

3(iii) a drainage basin that has recently been deforested: The curve is steep and the lag time is short. This is because there is less interception and overland flow because of the absence of trees.

3(iv) a long period of mainly light rain in summer: The curve is gentle and the lag time is long. This is because of less rain and because of more evaporation because of the summer sun. The tree canopy will also be at its highest at this time of year, so there is more interception.

3(v) a heavy rainstorm falling on thick snow in march: The curve is steep and the lag time is short. This is because the soil is frozen and so there is very heavy overland flow.

5. Hydrographs are useful to people for predicting floods and finding out how human activities like deforestation and urbanisation can affect the discharge rate of a drainage basin.

Water Balance

The water balance lesson, was not really the best lesson as there was no Mr. Heah :'(... anyway, The lesson taught us that the water that comes from the environment MUST go somewhere and cannot just disappear. It was given by the equation P = (change in S) + E + runoff [cant remember the variables. trying my best to recall what was taught without the help from the notes :D.

So, P = precipitation, change in S = change in the storage amount in the soil, E = evapotranspiration which is known as evaporation + transpiration and finally runoff meaning the amount of water that was not absorbed by the soil being flowed away to a water body like a river or a lake.

So we were given some situations:
1) Cloud Seeding
2) Damming
3) Agriculture
4) Urbanization
5) Grazing

Basically, we just have to determine what factors were affected due to these 5 activities, resulting in a change in the constants. :D

Thats about it
Choo Wen Yi