Stochastic generation of geomorphological instantaneous unit hydrograph‐based flow hydrograph

Abstract

The geomorphological instantaneous unit hydrograph (GIUH) can be represented as a sum of weighted probability density functions of the rainwater travel times for all plausible flow paths within a watershed. Using the kinematic‐wave routing procedure, the rainwater travel time for each overland or channel component is a function of the random channel length, slope and surface roughness coefficient due to their spatial variability. However, limited samples for random slope and surface roughness result in sampling errors which render the determination of statistical moments of component travel times as being uncertain. Hence, the resulting kinematic‐wave based GIUH (KW‐GIUH) is inevitably subject to uncertainty, which will be further transmitted to the design flow hydrograph. This paper develops a methodological framework to assess the uncertainty features of GIUH‐based flow hydrograph which, in turn, could be incorporated into constrained Gaussian simulation algorithm to generate randomly plausible design flow hydrographs.