Design flood estimation is the discipline of predicting a peak or design discharge for a catchment using deterministic methods (the rational method relating discharge to runoff coefficient, rainfall intensity, and area; unit-hydrograph synthesis; regionally-derived empirical equations) or statistical flood-frequency analysis, which fits extreme-value probability distributions (Gumbel's method, log-Pearson Type III) to observed annual maximum flows to extrapolate discharge magnitudes for specified return periods, together with associated confidence intervals. These estimated design floods are then linked to structure reliability/risk theory (probability of non-exceedance over a design life) and to flood routing (storage/level-pool routing via the continuity equation, and channel routing via the Muskingum method), which together form the core toolkit of engineering hydrology for sizing and operating hydraulic structures.
Design flood estimation is the discipline of predicting a peak or design discharge for a catchment using deterministic methods (the rational method relating discharge to runoff coefficient, rainfall …