Real-time Flood Forecasting
We’ve learned to predict typhoons. What is required to predict the floods they bring?
Flood Inundation Zone Estimation
With data about the volume and timing of flows in hand, we use geographic information system (GIS) data to estimate the regions that will be inundated by flooding, based on precise contour models of the terrain. Our objective in adding this model was to be able to forecast for civil authorities and the general public the actual neighborhoods most likely to be flooded when a typhoon of a given magnitude invades the area. Rather than generate a computationally very expensive three-dimensional hydrodynamic solution, we opt for the considerably simpler expedient of a mass-conservation approach, estimating the inundation zone by assessing precomputed volumes of water against the volumes of lower-lying areas defined in the GIS datasets. Figure 6 illustrates over-bank flows along the Sitze section of the Keelung River. The figure depicts color-coded inundation zones for various water depths and the corresponding inundation volumes.
The combination of the river channel flood-stage forecast model and the flood-inundation estimation model offers policy makers and flood-protection authorities a set of reliable and dynamic tools with which to predict oncoming floods, allowing them to issue timely warnings and launch appropriate emergency responses.