What method is used to calculate peak discharge in hydrology?

The Rational method is used to calculate peak discharge in hydrology because it provides a straightforward approach for estimating the peak flow from a specific area during a rain event. This method is particularly suitable for small drainage areas (generally less than 200 acres) and is based on the relationship between rainfall intensity, runoff coefficients, and the area of the watershed.

In the Rational method, peak discharge is calculated using the formula Q = CiA, where Q is the peak discharge, C is the runoff coefficient (which varies with the land use and type of surface), i is the rainfall intensity (typically taken as the average intensity for the duration of the rainfall event), and A is the area of the watershed. This method effectively simplifies the complex interactions of rainfall and runoff into a usable formula that can assist engineers and planners in designing adequate drainage systems and managing stormwater.

The other options, while they may involve aspects of hydrological analysis, do not specifically refer to the established method for calculating peak discharge in the way that the Rational method does. The elevation method, for instance, generally relates to topographic analysis rather than peak flow calculations, while the compounded area method and stormwater impact method may involve broader hydrologic modeling or assessments but are not standard for peak