Historical flood events 2013

Figure 7 shows the discharge inputs for the historical flood event in 2013. It shows that the initial discharge curves are below the forecast threshold 10 m<sup>3</sup> /s; therefore, the start of the prediction at 9 h is marked with a red line when one discharge hits the forecast threshold. Figure 8 compares the prediction of the inundation map of the first intervals of 3 h, 6 h, 9 h and 12 h with the inundation map from the hydraulic model of the historical flood event 2013. Table 3 shows the performance of the prediction for historical event 2013, evaluated by average RMSE for each individual ANN. The forecast performance is slightly better than that of the event 2006.

**Figure 7.** Hydrographs of the flood event in 2013. Seven discharge curves of three rivers and four streams are shown in different colors. The red line time marks the new start of the prediction at 9 h, where one discharge first exceeds the forecast threshold of 10 m<sup>3</sup> /s. The dash lines upon the discharge curves mark the different discharge sections for prediction inputs.

**Figure 8.** *Cont.*

**Figure 8.** Inundation maps from the prediction of water depths of the first intervals in flood event 2013. (**a**) ANN inundation map 3 h; (**b**) hydrodynamic inundation map 3 h; (**c**) ANN inundation map 6 h; (**d**) hydrodynamic inundation map 6 h; (**e**) ANN inundation map 9 h; (**f**) hydrodynamic inundation map 9 h; (**g**) ANN inundation map 12 h; (**h**) hydrodynamic inundation map 12 h.

**Table 3.** Numbers of wet grids and accurate grid percentages for the flood event in 2013. A wet grid is with the water level over 0.1 m; any water depth below this cutoff value is eliminated. The table shows grid numbers with larger RMSE and their percentages to the total wet grids.


Note: highlighted in gray are the percentages larger than 70%.

Historical flood events 2005

Figure 9 shows the discharge inputs for the historical flood event in 2005. Figure 10 compares the prediction of the inundation map of the first intervals of 3 h, 6 h, 9 h and 12 h with the inundation map from the hydraulic model of the historical flood event 2005. Table 4 shows the prediction performance of historical event 2005, evaluated by average RMSE for each individual ANN. As the forecast interval increases from 3 h to 12 h, the prediction accuracy drops. This can be evaluated by the grid percentage of RMSE.

**Figure 9.** Hydrographs of the flood event in 2005. Seven discharge curves of three rivers and four streams are shown in different colors. Time 0 marks the start of the prediction. The dash lines upon the discharge curves mark the different discharge sections for prediction inputs.

**Figure 10.** *Cont.*

**Figure 10.** Inundation maps from the prediction of water depths of the first intervals in flood event 2005. (**a**) ANN inundation map 3 h; (**b**) hydrodynamic inundation map 3 h; (**c**) ANN inundation map 6 h; (**d**) hydrodynamic inundation map 6 h; (**e**) ANN inundation map 9 h; (**f**) hydrodynamic inundation map 9 h; (**g**) ANN inundation map 12 h; (**h**) hydrodynamic inundation map 12 h.

**Table 4.** Numbers of wet grids and accurate grid percentages for the flood event in 2005. A wet grid is with the water level over 0.1 m; any water depth below this cutoff value is eliminated. Table shows grid numbers with larger RMSE and their percentages to the total wet grids.


Note: highlighted in gray are the percentages larger than 70%.

*4.2. Assessment of Real-time Forecasting of Water Depths for Multistep Flood Forecast Intervals, 1–5 h*

#### Historical flood events 2006

Table 5 shows the forecast for multistep forecast intervals of the event in 2006. The forecast for the event in 2006 has good accuracy for all the intervals.


**Table 5.** Forecast accuracy percentages for the flood event in 2006. This table shows the grid percentage to the total wet grids with average RMSE within 0.3 m. The forecast begins by the starting point, several hours later than the event beginning for the real-time forecast.

Note: highlighted in gray are the percentages larger than 70%.

## Historical flood events 2013

Table 6 shows the forecast for multistep forecast intervals of the event in 2013. The forecast of the event in 2013 has good accuracy for all the intervals, with a similar performance as that of the event in 2006.

**Table 6.** Forecast accuracy percentages rate for the flood event in 2013. This table shows the grid percentage to the total wet grids with average RMSE within 0.3 m. The forecast begins by the starting point, several hours later than the event beginning for the real-time forecast.


Note: highlighted in gray are the percentages larger than 70%.

#### Historical flood event 2005

Table 7 shows the forecast of multistep forecast intervals of the event 2005. The 3 h forecast of event 2005 still has a good accuracy of over 70%. For the 6 h, 9 h, 12 h forecasts, the ANN model produces less accurate results.

**Table 7.** Forecast accuracy percentages for the flood event in 2005. This table shows the grid percentages to the total wet grids with average RMSE within 0.3 m. The forecast begins by the starting point, several hours later than the event beginning for the real-time forecast.


Note: highlighted in gray are the percentages larger than 70%.
