She started off by showing us a picture of the part of the Nile that ran through Egypt. As we observed the picture, we noticed that the Nile looked GREEN. o.O However, as we were shown the zoomed in picture of the delta, we saw geometrical plots of green, indicating that these were agricultural plots of land, and not forests. Forests won't grow such perfectly straight and rectangular boundaries. Further up the Nile, away from the delta, there were buildings and much infrastructure as well as some agriculture. Upon further analysis of the picture from Google Earth, we noticed that Egypt was mainly established along the River Nile. Then, we were shown a picture indicating the population density of Egypt. Along the Nile, the population density was between 1000 to more than 5000 per sq km! However, further away from the Nile, was the Sahara, which had a population density of 0-10 per sq km. There was also a high population density in the Nile Delta, where there is much agricultural activity.
After we were shown the pictures, Miss Tang distributed clay to us, and we were to use it to make a model of the river system. We were given the various parts of the system, namely the delta, waterfall, meander, floodplains and levees, ox-bow lake and rapids, but were not told what went where. We were also not allowed to refer to our notes to find out what was what and what went where. After making our very professional and artistic models of the river system, we had a class discussion about the location of the various features of a river system. We learnt that the Upper Course Features (near the source) included waterfalls and rapids. Meanders and ox-bow lakes make up the Middle Course Features, and Lower Course Features would be deltas and floodplains and levees. Levees are mounts at the side of the river that normally consist of bigger and heavier sediments that the river had deposited. Floodplains contain smaller sediments deposited by the river.
Miss Tang then discussed some questions with us.
- Why are waterfalls and rapids near the source?
Because they need high ground and mountainous areas to exist. - Are meanders really slower (velocity)?
It looks like it! However, rapids and waterfalls may only look faster because there is more turbulence from the rocks, and so it looks faster and more violent. However, the middle course (i.e. meanders) may have a higher velocity as well because of the bigger volume and larger amount of energy. - What's the difference between meanders/ox-bow lakes and rapids/waterfalls?
The middle course features are on lower and flatter ground compared to the upper course features. - What do you see at the lower course?
- Sediment Deposition
- Sediments too heavy to be carried by river
- Velocity drops further
Done By,
Wong Hui Ying. (:
PS: Sorry if the font size is too small, I didn't know it was so puny and now I can't change it back. :P
