Temporal moment analysis of extreme flows in watersheds

Estimation of extreme flows is important for planning of hydropower production and as part of dam safety analyses. However, forecasts of extreme flows are uncertain because of a continuous change in the hydrological system due to climate and landscape changes as well as the extensive extrapolations that are needed due to relatively short data records. The analysis applied here utilizes kinematic-diffusive wave theory applied to the individual flow paths in the watershed network to describe the water discharge response following a precipitation event. The kinematic wave theory, particularly through the method of temporal moments, is used to parameterize compartmentalized runoff models. Channel geometry and a flood plain flow interaction give rise to significant non-linearity in the stage vs. discharge relationship and, hence, have marked impact on the prediction of extreme flows.