Identification of vegetation parameters for compound channel discharge as inverse problem

Abstract

Abstract In recent years many sophisticated models for discharge capacity of compound channels with vegetation have been developed. Despite the mature state of knowledge in this field, in a practice the simplest methods prevail and most of hydraulic models are based on the Manning formula. One of the reasons is that more complex methods require detailed characteristics on vegetation. The present study demonstrates that this issue can be solved by treating all such necessary variables as parameters to be identified in a sense of an inverse problem, using techniques of optimization. With a flume experiment as a case study, four models of a uniform flow were identified: Pasche, Mertens as complex methods, divided channel method (DCM) with Manning and Darcy–Weisbach equations as techniques used in a practice. Results showed that parameters for all methods can be found on the basis of minimization of model residuals, with the restriction that because of the larger number of parameters in complex methods, more observations are required. Methods of Pasche and Mertens with identified parameters provided a much better explanation of water depths than the Manning or Darcy–Weisbach based on the DCM. It is surprising that significant discrepancies between identified parameters and their real measured values were recorded. Even more, an almost perfect fit was obtained for different parameter sets.