WMS:Modified Rational Hydrograph

The Modified Rational Hydrograph also assumes that the time to peak is equal to the $t_{c}$, but allows for the duration of the storm to be longer than $t_{c}$, 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.

where:

• $t_{c}$ = time of concentration.
• $Q$ = Flow at time $t$, in cfs.
• $Q_{p}$ = Peak flow.
• $r$ = falling limb coefficient
• $s_{d}$ = storm duration

Related Topics

• Computing Hydrographs with Rational Method
• Rational Method Equation