Estimation of rating-curve parameters for sedimentation using a physical model

Parameters in the lumped sedimentation formula rating curve Q_s = KQ^P are discussed to estimate sedimentation in a basin without calibration in that basin. We were unable to determine the physical meaning of the parameters that are widely used by many researchers. A physically based sediment equation, the Itakura-Kishi equation, prepares a numerical experiment system to discuss rating-curve parameter characteristics. Experimental results suggest a method to estimate K and P parameters from geomorphologic data, particle diameter, riverbed slope, and roughness by changing experimental conditions. The results yield P from the particle diameter and riverbed gradient, and K from the exponential function of the gradient, particle diameter and roughness. Both the proposed rating curve and the Itakura-Kishi methods are applied to the Mekong River basin combining with the BTOP-MC (block-wise TOP model with Muskingum-Cunge routing) model, a distributed hydrologic model, to discuss estimations and their characteristics in practical fields. The proposed methods for K and P provide good agreement with mainstream data from the Mekong River under conditions of gradual water-level variation.