WMS:Modified Rational Hydrograph: Difference between revisions

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The Modified Rational Hydrograph also assumes that the time to peak is equal to the ''t<sub>c</sub>'', but allows for the duration of the storm to be longer than ''t<sub>c</sub>'', resulting in a trapezoidal shaped hydrograph as shown below. A coefficient to modify the slope of the receding limb may also be applied with this method.
The Modified Rational Hydrograph also assumes that the time to peak is equal to the ''t<sub>c</sub>'', but allows for the duration of the storm to be longer than ''t<sub>c</sub>'', resulting in a trapezoidal shaped hydrograph as shown below. A coefficient to modify the slope of the receding limb may also be applied with this method.


[[Image:ModifiedRationalHydrograph.png]]
:[[Image:ModifiedRationalHydrograph.png]]


where:
:where:


* ''t<sub>c</sub>'' = Time of concentration.
:* ''t<sub>c</sub>'' = Time of concentration.
* ''Q'' = Flow at time <math>t</math>, in cfs.
:* ''Q'' = Flow at time <math>t</math>, in cfs.
* ''Q<sub>p</sub>'' = Peak flow.
:* ''Q<sub>p</sub>'' = Peak flow.
* ''r'' = Falling limb coefficient
:* ''r'' = Falling limb coefficient
* ''s<sub>d</sub>'' = Storm duration
:* ''s<sub>d</sub>'' = Storm duration





Revision as of 17:32, 17 October 2017

The Modified Rational Hydrograph also assumes that the time to peak is equal to the tc, but allows for the duration of the storm to be longer than tc, resulting in a trapezoidal shaped hydrograph as shown below. A coefficient to modify the slope of the receding limb may also be applied with this method.

ModifiedRationalHydrograph.png
where:
  • tc = Time of concentration.
  • Q = Flow at time , in cfs.
  • Qp = Peak flow.
  • r = Falling limb coefficient
  • sd = Storm duration


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