Author(s): Hossam Elhanafy; Graham J. M. Copeland
Linked Author(s):
Keywords: Flood risk assessment; Adjoint sensitivity analysis; Numerical models; Shallow Water Equations
Abstract: This paper presents an analysis of the sensitivities of flood wave propagation to variations in certain control variables and boundary conditions by means of the adjoint method. This uses a variational technique to find the relationships between changes in predicted flood water levels and changes in control variables such as the inflow hydrograph, bed roughness, bed slope, and infiltration rate. The sensitivities can be used for optimal control of hydraulic structures, for data assimilation and for the analysis of the effects of uncertainties in control variables on the predictions of floods water levels. This method is developed and implemented through a numerical hydraulic model of channel flow based on the Shallow Water Equations (SWEs), forward model and the corresponding adjoint model that evaluates the sensitivities of the flood level to changes (uncertainties) in control variables. The equations are integrated using finite difference methods and a new modified method of characteristics is used to define the open boundaries. Results of validation tests on both the forward hydraulic model and on the adjoint model are presented.
Year: 2007