Explain the Rational Method for peak runoff estimation.

The Rational Method estimates peak discharge for small catchments (<200 ha): Q = CIA/360, where Q = peak discharge (m3/s), C = runoff coefficient (0.1-0.95), I = rainfall intensity (mm/hr) for duration equal to time of concentration, A = catchment area (ha). Time of concentration is time for water to travel from most distant point to outlet. Method assumes: uniform rainfall over area, peak occurs when entire catchment contributes, and constant C during storm. Limited to small catchments where assumptions are reasonable.