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Unformatted text preview: firstname.lastname@example.org < SEND NOTES GEOS 1004 Spotila Lecture 19, 11/12/09 EARTH SURFACE III: RIVERS AND STREAMS Rivers and lakes make up 0.009% of water in hydrologic cycle, but streams erode 80% of the land surface; running water shapes the lands surface. Rivers are also important for transportation, hydroelectricity, and engineering/floods. I. Aspects of river flow. ephemeral streams, arroyos = only have run-off, flow only after it rains. perennial streams, effluent streams = fed by groundwater, receive groundwater recharge, flow all the time. River or stream flow is quantified as discharge. discharge = volume of water flowing per time = average water velocity x cross sectional area of the river; e.g. cubic feet per second (cfs) or m 3 /s What is the relationship between velocity and discharge at a given location? Water velocity increases with discharge and water depth at a given location; like a falling column of water. How does river flow vary downstream? Why?- mountain stream = high velocity = 5 mph, lower discharge = 500 m 3 /s- lowland river = e.g. Mississippi, = slower velocity 3 mph, higher discharge = 17,500 m 3 /s The funneling effect of drainage area and the shape of river profiles II. Stream Form- How elevation changes as you go down stream, how a river looks on side view Stream form depends on stream power, or the ability to erode (do work). Stream form depends on stream power, or the ability to erode (do work)....
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