Development of a 1D-2D coupled hydrodynamic model for the Øyeren Delta in southern Norway

Abstract

In this study a coupled 1D-2D hydrodynamic model, MIKE FLOOD was used to simulate flood inundation extent, water levels and water velocities in the delta region of Lake Øyeren in southern Norway. The objective was to evaluate the improvement gained using a more complex framework. In addition, the credibility of existing flood zone maps made for Lillestrøm by Norges Vassdrag- og Energidirektorat (NVE) in 2005 was assessed. They were based on the assumption that the water levels predicted for Fetsund were applicable for the construction of flood zone maps at Lillestrøm. The model was set up and calibrated from historical hydrometric data as well as newly measured data. A methodology to correctly integrate the data required for flood inundation modeling was put forward. In addition, an assessment of the model sensitivity to various factors such as interpolation method, mesh resolution and model parameters was performed. The model performance seems to be greatly influenced by the quality of the digital elevation model (DEM), and hence also influenced by methods used to interpolate bathymetry, and mesh resolution. According to the results from the model, the assumption behind flood zone maps was determined to be conservative, overestimating water levels at Lillestrøm. The simulations also show a model capable of representing the hydraulic conditions of the delta, and demonstrate that the use of advanced numerical methods is now feasible, being an efficient way to obtain flood information.

Keywords MIKE FLOOD.Delta.Flood Management.Numerical methods.Model responses