Stream Eroded Landscape – Northeastern California One can outline a drainage bas
ID: 292889 • Letter: S
Question
Stream Eroded Landscape – Northeastern California
One can outline a drainage basin on a topographic map—see the example below. The drainage basin outline starts at a specified point on a stream (point A in this example, where the 2100’ contour crosses the stream). From there it goes straight up slope on both sides of the valley until it reaches the top of the drainage divide (A to B, A to C). Finally, the basin is outlined by closing the line from B to C by following the drainage divide around the drainage basin. Note that the outline never follows any contour—it always crosses contours perpendicularly. When rain falls on this landscape, the rain within the drainage basin will flow downhill through point A on the stream.
he Richardson Springs quadrangle map (in your lab manual or links below) shows a landscape shaped by stream erosion, with streams cutting valleys into the landscape separated by ridges. The major ridges serve as drainage divides, separating the water accumulating in one stream from water accumulating in adjacent streams. The water that flows in a stream is gathered in its drainage basin—the entire area of the landscape upstream and uphill from a particular point on the stream. Under uniform conditions of precipitation, a larger drainage basin produces more discharge than does a smaller drainage basin.
Runoff refers to the depth of water falling on a landscape that gathers into streams. A stream’s discharge is a function of the size of the drainage basin and the amount of runoff produced in a given period of time.
1. What is the contour interval on this map (Richardson Springs Quadrangle)? __________ feet
2. What is the total relief of the area shown on the map? _______________
3. What is the average annual discharge of the drainage basin? _________ cfs
4. The scale on this map is such that 1 inch=2400 feet. What is the percent slope of the stream from where it crosses the 1400’ contour to where it crosses the 1300’ contour? ____________%
5. What is the gradient along the same stretch of the stream in section 21 of the Richardson Springs quadrangle? _______________ft/mi. Assume the distance is 3/8th an inch on the map?
6. What is the percent slope of the stream in Section 30 of the Richardson Springs Quadrangle from where it crosses the 600’ contour to where it crosses the 500’ contour? _____________%
7. What is the gradient along the same stretch of the stream in section 30 of the Richardson Springs quadrangle? _______________ft/mi.
2100 | Map 9-4: Example of a drainage basin marked on a topographic map.Explanation / Answer
1. What is the contour interval on this map (Richardson Springs Quadrangle)? 20 feet
2. What is the total relief of the area shown on the map? 400 feet(average) (The highst point on the map is 2401 ft and the lowest contour is 2000 ft (on the north east part of the map).
The other questions cannot be answered using this map.