The San Diego Creek makes up the river system here. As it enters near 0 feet in elevation (sea level) the river winds to help slow down it's velocity. When the river winds, erosion and deposition of sediment is more prevalent in some areas more than others.
You can think of a river like wind. There are areas of high pressure and areas of low pressure. High pressure wind make rocks erode more quickly than low pressure wind. The same principles apply here. When the San Diego Creek is flowing in a near straight line, not one side favors the other in high or low pressures. When the river turns unexpectedly, things get interesting. This turn is called a bend or meander.
When the river turns to the right, there is high pressure on the left, which creates more drag and more erosion of sediments along the bank. Likewise, on the other side of the river, there is less pressure. So the water on the right side of the bend moves slower and sediment can be deposited along the bank. This makes the river move, over time, to the left.
When the river turns to the left, there is high pressure on the right. More water is hitting the bank at higher speeds than the left, so more sediment is taken by the river. Likewise, on the other side of the river, the water is moving much more slowly so sediment is being deposited. This will eventually make the river move to the right overtime.
High pressure means high velocity of water and low pressure means low velocity of water. The more velocity the river has on one side, means more erosion on the same side. The less velocity, means more will be deposited from tiny particles already being carried by the river. Where there is high pressure, it usually means larger particle size. This is due to the fact that the high pressure has to cut into new rock verses the other side which is only depositing already eroded material. On the low pressure side, you will likely see smaller, more fine particle size. You can think about this phenomena like a circular racetrack. The cars on the outer edges have to go faster and the cars on the inner edges have to go slower to match the speeds of the cars in the middle or the average speed of the cars.
Works Cited
http://www.briangwilliams.us/geology/visualizing-erosion-and-deposition-in-a-meander.html
http://study.com/academy/lesson/speed-and-velocity-difference-and-examples.html
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1. "Newport Back Bay" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. Note, this IS cheating as only the person who sent their answers has learned something, while the others get a "free ride". It's not fair to others. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching.
2. From this vantage point, describe the similarities and differences in sediment particle sizes between both sides of river banks AND your explanation as to why this might be. No need to swim across the river to find out.
3. How many meanders are present from this vantage point looking up and down the river?
4. For each meander you see, which side of the river has the highest pressure or water velocity? Which side has the lowest? You should have two answers per meander.
5. Using the first diagram on this cache page, which option (A, B, or C) would best fit this section of the San Diego Creek when comparing water velocities?
6. If a flood would happen, how would the river delta react?
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