A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Eng.) - Asian Institute of Technology, 1972

This study presents a method for. simulating the geometry of a natural channel with an artificial one having a prismatic cross section. Stages for three different discharges at all sections of the natural river are utilized to find the bed elevations and the Manning's coefficients at all sections of the simulated channel. A scientific subroutine called RTMI is used to determine the root of the non- linear equations required to describe the simulated system. This subroutine adopts the Mueller's iteration scheme of successive bisection and inverse parabolic interpolation. Good agreement is found between the stages in the natural and simulated channels for steady discharges. At some sections of the simulated channel, the square of Manning's 'n' is found to be negative; however, stages at these sections are almost identical to those in the natural rivers for the same discharges. The best agreement between the stages of the natural and simulated channels occurred when the bed slope for the most down stream reach of the simulated system was assumed to be equal to the slope of the water surface in that reach of the natural channel. The slope of all upstream reaches were considered as variables.