Mathematical modelling for formation and propagation of floods in a data-deficient basin

Abstract

Abstract Applicability of some rational concepts and techniques to real-world river basin problems with the usual limitations with regard to the data available was investigated. Two distinct but interrelated hydrologic processes, one of flood formation in a basin and the other of flood propagation down a river channel, related to the Jhelum River basin in the Kashmir Valley in India were considered for appropriate modelling. For the former, the concept of instantaneous unit hydrograph (IUH) representing the basin response in transforming the incident rainfall into flood runoff and the Nash model for deriving the IUH were applied. In such an application, the effects of the lumping of the varying intensities of rainfall occurrences into daily rainfall amounts on the derivation of the two Nash model parameters and on the reproducibility of the peaks of flood runoff through convolution of the IUH with the observed rainfall have been indicated. Further investigation into the analysis of all aspects of these effects is needed to arrive at definitive conclusions. For the other process, a modified Muskingum method based on a finitedifference approximation of the diffusive transport equation is proposed. As a concomitant requirement in this study an expression for variation of Manning's roughness coefficient with stage and a mathematical formulation for river rating for all stages of flow including flood flows have been obtained and tested for their validity for a particular section of the Jhelum River.