What is the Rational method in hydrology?
The Rational Method expresses a relationship between rainfall intensity and catchment area as independent variables and the peak flood discharge resulting from the rainfall as the dependent variable. It has been used for over 150 years, and known as the Rational Method for nearly 100 years.
How do you find the Rational method?
The Rational method predicts the peak runoff according to the formula: Q=CiA, where C is a runoff coefficient, i is the rainfall intensity, and A is the subcatchment area. This formula is applicable to US or metric evaluation, as long as consistent units are employed.
How do you use Rational method to calculate runoff?
The Rational Formula is expressed as Q = CiA where: Q =Peak rate of runoff in cubic feet per second C =Runoff coefficient, an empirical coefficient representing a relationship between rainfall and runoff.
What is Rational method of design?
The Rational Method is a set of formulae used to determine the peak discharge expected from a soil conservation structure design, such as a contour bank. The Empirical version is a simplification of the full Rational Method which uses parameter values that are based on experience or observation.
How do you construct a hydrograph using the Rational Method?
The Standard Rational method simply computes the peak flow, Qp = CiA. The resulting hydrograph is an isosceles triangle. Standard Rational method hydrographs peak at time, Tc and have a total duration equal to 2 x Tc….Standard Rational Method.
| Receding Limb Factors for the Rational Method | |
|---|---|
| <0.30 | 1.67 |
What is a rational form?
noun Mathematics. a quotient of two polynomials with integral coefficients.
What is the origin of the rational method?
According to documented history, the Rational method was first used in 1851 in Ireland and by 1889 it was rampant in North America. Thank Emil Kuichling. It took some time before American Highway engineers embraced it because apparently there weren’t clear instructions on how to apply it.
What is the Modified Rational Method used for?
The Modified Rational method takes the Standard Rational to a different level in order to yield a hydrograph mainly for use in detention pond design. According to the Rational method, the highest Qp occurs when the rainfall duration equals Tc.
What are the 3 types of rational functions?
Rational functions can have 3 types of asymptotes: Horizontal Asymptotes. Vertical Asymptotes.
What is rational number example?
Any number in the form of p/q where p and q are integers and q is not equal to 0 is a rational number. Examples of rational numbers are 1/2, -3/4, 0.3, or 3/10.
What is Rational method used for?
One of the most commonly used procedures for calculating peak flows from small drainages less than 200 acres is the Rational Method. This method is most accurate for runoff estimates from small drainages with large amounts of impervious area. Examples are housing developments, industrial areas, parking lots, etc.
How is critical storm duration calculated?
The critical duration is determined by comparing various durations of the specified storm and calculating the peak wet weather flow rate and volume of runoff for each. The duration resulting in the highest peak wet weather flow rate or largest total volume is the “critical duration” storm.
What is the Wallingford procedure?
The Wallingford Procedure is a complete methodology for the design and analysis of urban drainage systems. It is invaluable for all those engaged in or responsible for urban drainage. Of the original 5 volumes published in 1981, only 3 volumes are still relevant today. All documents are available in pdf format.