Framework for Offline Flood Inundation Forecasts for Two-Dimensional Hydrodynamic Models

Abstract

The paper presents a new methodology for hydrodynamic-based flood forecast that focuses on scenario generation and database queries to select appropriate flood inundation maps in real-time. In operational flood forecasting, only discharges are forecasted at specific gauges using hydrological models. Hydrodynamic models, which are required to produce inundation maps, are computationally expensive, hence not feasible for real-time inundation forecasting. In this study, we have used a substantial number of pre-calculated inundation maps that are stored in a database and a methodology to extract the most likely maps in real-time. The method uses real-time discharge forecast at upstream gauge as an input and compares it with the pre-recorded scenarios. The results show satisfactory agreements between offline inundation maps that are retrieved from a pre-recorded database and online maps, which are hindcasted using historical events. Furthermore, this allows an efficient early warning system, thanks to the fast run-time of the proposed offline selection of inundation maps. The framework is validated in the city of Kulmbach in Germany.

A 2D Real-Time Flood Forecast Framework Based on a Hybrid Historical and Synthetic Runoff Database

“…The fitting between two series is considered good if the values of NSE and Wr2 are close to one. The first parameter to be considered is the NSE: the event giving the best value over 0.85 is selected [5,23,24]. In case no NSE is found higher than 0.85 the event with the best Wr2 over 0.85 is used.…”

“…They can also provide forecasts of the magnitude and extension of flood events and on the severity of possible damages, providing a valid and effective tool for practical emergency management. In order to prevent and mitigate casualties and economic losses, the EU Floods Directive clearly states that flood risk management plans should take into account flood forecasts and Early Warning Systems (EWS) built in a way that they are able to consider the characteristics of a river basin or sub-basin [5,6]. Thus, researchers and engineers have been extensively working on the development of cost-effective and rapid methods in the last decades [7].…”

“…The main limitation of those studies is that the forecasts have a coarse spatial and temporal resolution. The vast majority associate the flood inundation extents to a single exceedance level, usually 100-year return period [5,20], or a limited number of scenarios [19].A different approach, with a fine resolution and a wide range of discharge forecast, is presented by . The method is based on an offline database of high flow runoff curves and corresponding 2D inundation maps previously simulated with a fine spatial and temporal resolution.…”

“…The offline flood maps are selected based on the forecasted discharge hydrographs in the gauges located upstream of the study area and the available simulations stored in the offline database. The term "offline" refers to maps retrieved from a pre-recorded database, as opposed to online which refers to maps produced at real-time [5]. In this paper, we focus on improving the runoff database by including scaled historical flow data series in order to provide a more robust hybrid database.…”

“…The main limitation of those studies is that the forecasts have a coarse spatial and temporal resolution. The vast majority associate the flood inundation extents to a single exceedance level, usually 100-year return period [5,20], or a limited number of scenarios [19].…”