Real-time error correction of two-dimensional flood-inundation simulations during rainstorm events

This study develops a real-time error correction model named RTEC_2DIS for two-dimensional (2D) flood-inundation simulations. Inundation depth and flooding area provided by a 2D numerical hydraulic modeling (SOBEK model) are corrected in accordance with real-time observations at specific road-based water-level gauges. The proposed RTEC-2DIS method can estimate the forecast error of inundation depths for various lead times at both gauged grids and ungauged grids within the watershed/basin. By doing so, the real-time correction of the resulting inundation area composed of corrected water-depth forecast at all concerned grids can be achieved by adding the water-depth forecasts to the corresponding forecast errors. In this study, the demonstration of the model is made in the Tainan district in Southern Taiwan under the consideration of the design rainstorm events of specific return periods with a central-peak storm pattern and a real rainstorm event from Typhoon Megi in 2016. The results from the numerical demonstration indicate that the RTEC-2DIS method can effectively reduce the uncertainty in the estimating inundation depth at gauged grids to enhance its correction performance with the percentage of error reduction of 42% in the case of the real rainstorm event. Furthermore, regarding the design events, through the proposed RTEC-2DIS method, the accuracy of the simulated inundation area can be improved by 55%. In summary, the proposed RTEC-2DIS method not only can correct forecasted inundation depths at gauged grids, but also facilitate the accuracy and reliability of the resulting inundation area in accordance with real-time observations recorded at road-based water-level gauges.