This calculator helps civil engineers and hydrologists estimate runoff using the Rational Method, a widely used technique in hydrology for small watershed analysis.
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte: "Hydrology Handbook", ASCE Manual No. 28. Read more
The rational method formula: Q = C \times i \times A, where:
Given: C = 0.75, i = 2 in/hr, and A = 10 acres. The runoff is calculated as: Q = 0.75 \times 2 \times 10 = 15 cfs.
The Rational Method is used to estimate the peak discharge of runoff from a watershed during a storm event, particularly for small watersheds.
The runoff coefficient depends on land use, soil type, and surface conditions. Tables are available in engineering handbooks to guide selection.
The Rational Method is typically only used for small watersheds (less than 200 acres) because it assumes uniform rainfall intensity across the watershed.
The formula uses C as a dimensionless number, i in inches per hour, A in acres, and Q will be in cubic feet per second.
Yes, the Rational Method is particularly useful for urban drainage systems where rapid runoff estimation is required.