TR(BR)-117A : Effect of downstream boundary conditions on the propagation characteristics of the Dam Break flood

Abstract

The understanding of the flood wave propagation is primarily based on the popular St. Venant's equations. The non-linear nature of these equations resorts to using a numerical scheme for solving them. The Four Point Finite Difference Implicit Scheme (or Preissmann Scheme) requires a downstream boundary condition for solution. The normally used boundary condition is the unique-steady state rating curve supplied through channel control. The actual boundary condition may however, not correspond to the user supplied boundary condition. It therefore, may lead to emoureous computations.

The present report endeavours to study the above aspect with the help of the quantified hysteresis (dimensionless) of the rating curve. The criteria developed for defining the wave types may further help apply approximate flood wave models in Hue of St. Venant equations (or full dynamic wave model).