3.4 HYDRAULIC MODELING

Flooding modeling software
    • IBER

Introduction: IBER is a 2D mathematical model for the simulation of free surface flow in rivers and estuaries. Processes such as sediment transport, turbulence and water quality can also be simulated. In the present work, model setting-up, and two small Exercises are presented to illustrate IBER functioning.


Aim: The setting-up process is presented by using Exercise 1, which consists on a torrential river in Comarruga, Catalonia, north-east Spain. Near the river there is a residential area, where flooding assessment is carried out. Results for different configuration of the model are presented for Exercise 1.

Exercise 2 consists on a torrential stream located in Pineda de Mar, a touristic village in the same region. Again, in this exercise, 2D hydraulic model is built with IBER in order to asses flooding in the village for different Manning coefficient values for the residential area.


Result Exercise 1: The results presented in this section correspond with three different model configurations as explained below:

  • Configuration 1: Mesh without subtraction of buildings; Manual land use assignation.
  • Configuration 2: Mesh subtracting buildings and with finer mesh size (1m) in lines surrounding buildings location; Automatic land uses designation.
  • Configuration 3: Mesh subtracting buildings and including levee to protect the residential area from flooding. Finer mesh size (1m) in lines surrounding building and levee; Automatic land uses designation.

It can be seen in Figure 10, that by using Configuration 1 and 2 in the simulation, flooding is occurring in the village near the river. The inclusion of a wall along the river (Configuration 3), efficiently protect the village against flooding.

The use of a more detailed mesh for the simulation doesn’t have an important effect in the results. This is explained due to the characteristics of the DEM, which is representing the height of the existing buildings in the area.

The use of different approaches for the designation of Manning coefficient values have a slight impact on the occurrence time of flooding. This can be confirmed in Figure 11 that shows the variation in time of water depth for the same point location by using two different configurations.


Results Exercise 2: The maximum flooded area, for different Manning coefficient values in the residential area are shown in Figure 17. It can be seen that in all cases, great areas are flooded including important infrastructure such as the train rail.

The change in surface roughness has a minimal, or neglectable effect, in the left floodplain (in relation to the river flow direction) of the domain. Some variations are found in the case of the right flood plain. There is an increased in the maximal flooded area when using higher manning values (Figure 17). Nevertheless, the increased flooded area has a water depth that is always below 10cm.

Due to the constant presence of flooded areas in the top boundary of the domain, it is advisable to extent back this domain to better assess the real extension of flooded areas.

Report to IBER


    • CITYCAT

Report to CITYCAT

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Networks modeling software
    • Mike 21

Report to Mike 21


    • Mike 11

Introduction: Mike 11 is a commercial software provided by DHI/DK. We use it to model the 1D rivers with the Saint Venant equations and the finite differential method of the Abbott-Lenesco scheme for calculations.


Aim: We use Mike 11 for the analysis of a channel and a river branch similar to Var.


Result: The profile is similar at first sight but the heights are different.

As we can see in the result, change of different parameters leads to different results. For example, if we increase the bed resistance from 15 to 80, water level decrease relatively, it will not change the form of water level in the river, there is no grand change for the water level graphics for every cross section.

In Figure 10, the water level exceeds the level of the river dikes. This leads to flooding upstream of the threshold at the 15200 chain.

The impact of the threshold in the channel is visible. A decrease in the water level behind the weir is observed when a larger opening is defined for the structure. The water near the threshold had not reached the bank. Flooding in this area was avoided.

The difference in the depth of water produced by the threshold shows that the geometries of these structures must be taken into account to avoid flooding.

If we change the size of the weir, first, we change the width of the weir from 50 to 100 without change the length and height (relative position to the topographic). As we can see from figure 12 and 13, the water level decrease which is logic because with the surface of the cross section increase, water level decrease

And if we change the relative position to the topographic and the size of the weir, from figure 12 and 14, we found that water level increase which is logic too, and the difference between them is approximately 5 meters.

Report to Mike 11

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