Runoff discharge and sediment load

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Runoff discharge and sediment load

March 13, 2014

Mike Mctee provides a brief report on the estimation of runoff discharge and sediment load during a period of rain and snow melt on the 6th of March, 2014.

Estimating runoff discharge and sediment load Mike McTee On Thursday March 6, 2014, over 0.5” of rain fell on two feet of snow. Most of the snow below 4000’ melted. Runoff collected sediment while flowing towards draws. In lower Partridge Alley, which drains about one square mile, we measured the cross sectional area of a channel and runoff velocity to estimate discharge. Water samples were taken to estimate sediment load.* At 6 pm, discharge equaled 20 cfs (cubic feet per second) which would be similar to summer flows of a small creek. Sediment load concentrations equaled 1500 mg/L– about ten times higher than expected for a stream under normal conditions. If those conditions continued for one day, 10 million gallons of runoff would carry 150,000 lbs of sediment! These results demonstrate the capacity for floods to change a landscape.