Part III. Rivers-Answer in space provided in answer sheet (10 pts) 5. The Amazon
ID: 115953 • Letter: P
Question
Part III. Rivers-Answer in space provided in answer sheet (10 pts) 5. The Amazon Basin is the largest in the world, and the river is 6452 km long with an elevation drop from 4500m to sea level (0m). Be sure to show your work and use scientific notation as appropriate a. (1.5 pt) Calculate the gradient of the river from headwaters to mouth. b. (1.5 pt) The Amazon empties into the Atlantic at Belém, Brazil, but ocean-going ships can travel as far inland as Manaus, 1600km from the Atlantic. What is the gradient of the river from Manaus to Belém if Manuas is 30 meters above sea level? c. (3 pt) Draw a rough sketch of the longitudinal profile of the river from headwaters to mouth. Be sure to label the drawing well. d. (2 pt) If sea level rose 10 meters, how far inland would the rising sea reach? **May help to draw on your schematic profile in part C. e (2 pt) What would the new gradient from headwaters to mouth be? Please note that you might find this answer surprising.Explanation / Answer
a. Gradient of the river = Elevation Difference / Horizontal Distance
Given that elevation drops from 4500 m to sea level (0 m) in 6452 km.
Thus the gradient of the river is, (4500/6452) or 0.697 m/km.
b. Elevation of Manaus is 30 m.
Elevation of Belem is 0 m (as it is on the sea level)
Distance from Belem to Manus is 1600 km.
Thus the gradient of the river from Manaus to Belem is (30/1600) or 0.01875 m/km.
d. We have calculated that the gradient from Manaus to Belem as 0.01875 m/km i.e. the river rises about 0.01875 m per km from Belem to Manaus.
Thus to rise 10 m the river will need (10/0.01875) km 533.33 km.
Thus the Sea will reach up to 533.33 km inland.
e. If the sea reaches 533.33 km inland the total Horizontal distance of the river will be (6452-533.33) or 5918.67 km
THe new elevation difference will be (4500-30) or 4470 m.
Thus the new gradient will be (4470/5918.67) 0.755 m/km