Water depths and velocities flooded areas
3.5 Water depths and velocities flooded areas
For the Stadswerven area it was necessary for the urban planners to be able to anticipate on the flooding conditions which occur when Stadswerven becomes flooded. The maximum reached water depths and velocities of the flooded area were therefore calculated. This gave an impression of the possible severity of the flood conditions at Stadswerven. Higher water depths and velocities can cause damage and casualties
A 2D inundation model was developed (see Appendix B) to calculate the flooding depths and velocities. The model simulates a flooding of Stadswerven in the present state. No elevation of the present ground level was applied. For the calculations a traditional urban building plan was implemented. Flooding is caused by a dominating extreme river discharge resulting in a water level at Stadswerven of NAP +3.1m. and NAP +3.4m. A water level of NAP +3.1m has a return period of 4000 years at present and a water level of NAP +3.4m is the predicted design water level for 2100. A flooding caused by an extreme storm surge was not considered because this would not provide additional information. For both type of floods, the maximum reached river levels are equal but the duration of a flood caused by extreme river discharges is larger than the duration of a flood caused by an extreme storm surge (see Figure 3.10 and Figure 3.11). The period of flooding of the study area will therefore also be larger for floods caused by a extreme river discharges. The effect of waves were not included into these calculations. The flooding results are illustrated in Figure 3.14 to Figure 3.17.
Figure 3.14 Maximum water depths (m) when the maximum water level in the river reaches NAP
+3.1m.
Figure 3.15 Maximum water velocity (m/s) when the maximum water level in the river reaches NAP
+3.1m,
Figure 3.14 and Figure 3.15 show that for a flooding corresponding with a river level of NAP +3.1 m only the area along the river becomes flooded and water depths are mostly in the range up to 0.75 m. These results show that the ground levels of the study area in the present situation are already quite high. The water velocities are low. Only in specific areas does the water velocity exceed the 0.1 m/s range.
Figure 3.16 Maximum water depths (m) when the maximum water level in the river reaches NAP
+3.4m, the predicted design water level for 2100
Figure 3.17 Maximum water velocity (m/s) when the maximum water level in the river reaches NAP
+3.4m, the predicted design water level for 2100
For a flooding corresponding with a river level of NAP +3.4 m, the entire peninsula becomes flooded. The maximum water depths reach up to 0.75 m. The maximum velocities only exceed 0.25 m/s in a few areas.
From the flooding calculations it can be concluded that the flooding severity of the Stadswerven area is not very high. Maximum water depths and velocities within the study area are relatively low. In the majority of the Stadswerven area, the water depths do not exceed 0.75 metres, and water velocity are below 0.25 m/s. Water forces at these values are low and the situation is safe enough to wade through the water. The restrictions on the application of building concepts and public area architecture is therefore low which provides the possibility for a wide range of building concepts and flood proof sollutions.