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PART 2 FINAL
PHYSICAL GEOGRAPHY 106
CALCULATE AND ANSWER ALL OF QUESTIONS BELOW
KNOW THE ANSWERS TO ALL THE FOLLOWING QUESTIONS AND....
BRING THE ANSWERS WITH YOU (IN YOUR MIND OR ON A SHEET OF PAPER) TO THE FINAL EVALUATION.
THESE QUESTIONS WILL BE PART OF THE MULTIPLE CHOICE EVALUATION.
Dr. M. Mustoe

This part of the evaluation is concerned with the relationship between water velocity and competency in stream flows. It also introduces a theoretical concept known as The Sixth-Power Law.

STEP 1
Read the article written below.

THE SIXTH POWER LAW
M.Mustoe

A relationship exists between the velocity or speed of the flow of a river, the size of the particles that can be eroded, deposited....that is ....moved or transported, and what is known as boundary shear stress. Some particles such as silt or clay, that stick adhesively together, require a little more energy to get them flowing into the stream's bedload. Bedload is the sediment that flows suspended in the water near the bottom and sometimes in contact with the bottom of the stream. Sediments such as pebbles, cobbles and gravels require higher velocities of the water to take off or be transported from the bottom of the stream bed or the stream's walls because these particles are heavier in weight.

A stream's competence is the maximum size of particle that can be transported by the stream at a given discharge velocity. What's interesting is where the power of kinetic energy comes in with respect to these sizes of particles. It has been worked out to show that there is a mathematical relationship that exists between the increase in the velocity of a stream with the size of the particles. This relationship is stated as the Sixth Power Law. It's pretty simple, but it really reflects the power that exists in water when it is moving. Essentially a particle at rest on a stream bed is at rest when the force of the water surrounding it equals the resistance exhibited by the particle. There's my favorite word embedded into this statement....equilibrium. Once the velocity of the water exceeds this equilibrium...then...the particle moves. The largest radius of a particle that a given velocity can kick into motion is stated as The Sixth Power Law.

Now, I deliberately used one of my favourite fonts (first grader) on the above so as to attenuate the impact of these scary looking numbers for some of you. What this is saying is:

STEP 2
After you have read the segment on the sixth-power law....then consider the following question(s) and do the calculation. Bring the answer with you to class.

1. Consider a stream which increases its velocity from 3 m/sec to 6 meters per second. If the stream originally carried a load of particles averaging 0.2 grams, theoretically the maximum size of particles the stream could carry at its increased flow would be?

2. Bedload is defined best as:
a. volcanic material suspended in water.
b. material used in making road bed.
c. sediment being carried by water near the bed of the stream.
d. an alluvial fan.

3. The statement: "The biggest particle that a stream can pick up at Spring flood stage is 3 centimeters. Is referring to the __________________ of the stream.

The following does not use the 6th power law....but deals with water force.

4. Water moving at 4 mph exerts a force of 66 pounds per sq foot. Given a car moving through water (water moving at 4 mph) and exposing a surface area of the car of about 15 square feet (that is, the car is going through moving water that is running up a little higher than the bumper). What is the total force (derived from the water) that will be exhibited on the car?

4b. Water weights about 64.2 lbs. per cubic foot. An average down flow velocity of water is anywhere from 6 to 12 mph. If you drive a 1500 pound automobile into this moving water and it stalls, there is an estimate of 500 pounds of force from the water that will be applied to the vehicle for every foot of rise in the water level of the stream. In addition, for every foot the water rises up, the vehicle will displace 1500 pounds, (the weight of the automobile) This is the buoyancy force of the car. In essence for every foot of rise in the water, the car weighs 1500 pounds LESS. When buoyancy lifts the vehicle and exceeds the frictional force that "sticks" the car to the road, lateral force will push the floating car down the stream. So about how many feet of water would it take to float/move a 1500 pound vehicle? I'll give you the answer.....it doesn't take much more than two feet to float your car. Don't drive in flood waters. It is not worth the risk. More people die by drowning in severe weather than from any other form of severe weather.

REGARDING SOIL POROSITY

Soil porosity is the physical amount of space there is between soil particles. It is an important measurement especially when dealing with the moisture factors of the soil for issues such as mass wasting as well as agriculture. The way you determine soil porosity is by taking a sample of a completely dry clump of the soil at issue, and infuse it with water until it cannot hold any more of the water. Here is the procedure:

A. Weigh out the dry core sample in grams.
B. Wet the sample until saturated and weigh the saturate sample.
C. Find the difference between the two weights above. This gives the Cubic Centimeters (CC) of the water in the sample.
D. Divide the CC of water by the CC of core sample and multiply this by 100.
E. This procedure provides the percentage of pore space which is the porosity of the soil.

5. Determine the porosity of a soil that has is sampled with a 400 cc clump of dry soil that weighs 600 grams (when it's dry). When this sample is saturated. this soil has a weight of 760 grams. What is the porosity of this soil?

And that's all folks. Remember to bring your data to the meeting on the day of the FINAL