TOPOGRAPHIC MAP REVIEW FOR DRAINAGE BASIN MAPPING This map is contoured in feet.
ID: 284276 • Letter: T
Question
TOPOGRAPHIC MAP REVIEW FOR DRAINAGE BASIN MAPPING This map is contoured in feet. The contour interval is: ________ feet. The elevation of point X is: ________ feet. The elevation of point B is: ________ feet. The elevation of point A is: ________ feet. The distance from A to B is: mile(s). The gradient from A to B is: feet per mile. Lightly shade or color the area inside each closed contour that represents a hilltop, then draw a dashed line to indicate the drainage divide that surrounds Trout Run drainage basin. Trout Run flows (drains down hill) in what direction? _______Explanation / Answer
Answer:
a) 20 feet. ( Contour interval is the difference between 2 successive contours. In the map, elevation of only 2 contours has been provided. They are 100 feet and 200 feet. Between these 2 contours there are 5 contour intervals or spaces. To find contour interval of each find the difference between the 2 "tagged" contours i.e. 200-100 and divide it by the number of contour intervals/spaces. So we get 100÷5 = 20. Use the appropriate unit of height given, which in this case is feet.
b) 240 feet. ( drainage always occurs from a higher point to a lower point. Since there appears no drainage at X, it is at an elevated position. The bold contour enclosing it has an elevation of 200 feet. Since Contour interval is 20 feet the next contour will be 20 feet higher than 200. This will be 220 feet. Since point X lies on the contour subsequent to 220 feet, it's elevation will be 240ft.
c) 100 feet. (Since it lies on the 100 feet contour)
d) 180 feet. (Point A lies on the 4th contour after the 100feet contour and on the contour just before 200 feet. Considering the contour interval, A is at 180 feet.
e) 1 mile. ( mark the scale of the map on your measuring ruler. Now measure distance between point A an B. The distance, in this case, is the same as that of the scale i.e. 1mile.)
f) 80 feet per mile. (Gradient is defined as the ratio of vertical difference between the 2 elevations to lateral distance. 180 ft ( elevation of point A) - 100 ft (elevation of point B) = 80 ft. 80ft÷ 1mile (lateral distance between the 2 points).
g) colour the area enclosed by the bold 200 feet contour. Then join these tops to get the divide.
h) south direction
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