## 5 Results and Discussion
### Streets Speed Changes  
For a better understanding and management of the transportation system, the impact of the spatial variation of flood is crucial. To this end, the traffic conditions on every street were aggregated for a day interval. In order to identify and quantify the differences between the normal and flooded situations, Figure 7 shows the speed differences between these two conditions for the whole road network during a day. The speed reduction indicates that traffic was slower on a particular road during flood than it was under normal condition.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Effect on Travel Time**} & \multicolumn{2}{c}{**Effect on Travel Distance**} \\ \hline \multirow{2}{*}{**Trip Duration**} & **Dry** & **Flooded** & \multirow{2}{*}{**Travelled Distance**} & **Dry** & **Flooded** \\  & **Conditions** & **Conditions** & & **Conditions** & **Conditions** \\ \hline Sum (hours) & 109,201 & 137,883 & Sum (km) & 21,383,980 & 23,514,722 \\ Absolute difference (hours) & - & 28,682 & Absolute difference (km) & - & 2,130,742 \\ Relative increase (\%) & - & 26 & Relative increase (\%) & - & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Flood effects on travel time and travel distance.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Travel Distance** & **8–9 h** & **12–13 h** & **Overall (0–24 h)** \\ \hline Dry condition (km) & 1,639,482 & 1,729,737 & 21,384,880 \\ Flooded condition (km) & 2,038,912 & 2,829,310 & 23,492,319 \\ Difference (km) & 399,430 & 1,099,573 & 2,107,439 \\ Variation (\%) & 24 & 64 & 10 \\ Vehicles with longer routes (\%) & 11.7 & 18.3 & 16.2 \\ Rerouted vehicles (\%) & 19.3 & 25.8 & 26.9 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Flood effects on travel distance.  
Generally, it is difficult to predict where the traffic congestion will build up, but certain spots consistently received slower traffic during the flood. These locations are zoomed and marked by numbers on the map. They could be argued as the most vulnerable sections of the transportation network. From Figure 7 it is clear that the progressive flood had a domino effect of the reduction speed on the whole network. The flooded roads and bridges are shown with the red color. By moving from the river toward the border of the region, the flood effects on the road sections have been decreased. Roads nearby the river, especially where the flooded roads were the only way to reach rest of the region from that isolated by flooded neighborhoods, experienced the most reduction speed because of the flood and they are shown by number 1. Vehicles in this location were locked about 4 h from 13:00-17:00 Location 2 in normal situation has registered slow traffic, but traffic problems during the flood worsen for an extended duration. The red road segments nearby the location 2 were flooded for 5 h between 11:40 and 16:40, but the traffic disruption lasted 7 h with purple road segments being reduced with 40-50 m/s. It is worth noting that, while most vehicles faced traffic delays, some traveled faster than usual. Some roads, immediately after a road closure point, had reduced traffic loads, and thus vehicles could move faster. Location 3 is an example of these roads.