Design Flood & Hydrograph Estimation

Estimate the design flood for a catchment: a quick peak discharge using the Rational method, or a complete design flood hydrograph using the CWC Flood Estimation Reports (Synthetic Unit Hydrograph) approach.

Select an Estimation Method

1. Peak Flood – Rational Method

Computes the peak discharge using Q = 0.278·C·I·A. Rainfall intensity (I) is evaluated at the catchment's time of concentration (tc), with land-use based runoff coefficients (C).

Suitable for small catchments (≤ 50 km²). Gives peak discharge only.
Open Peak Flood

2. Flood Hydrograph – CWC Method

Derives a Synthetic Unit Hydrograph from catchment characteristics (A, L, Lc, S) using CWC sub-zonal regression equations, then convolutes it with a critically sequenced design storm (PMP / SPS / T-year) to produce the full Design Flood Hydrograph.

For medium to large catchments. Gives the complete hydrograph (e.g. PMF).
Open Flood Hydrograph