Graduation of Stan Vernimmen

The water levels along the dike of Kampen are mainly affected by the magnitude of the discharge on the river IJssel and the wind characteristics on the IJsselmeer. The Kampereiland has been assigned as a retention area to reduce the water levels near Kampen. This area should store excess water during a storm at the IJsselmeer of a magnitude corresponding to a probability of 1/500 per year, to prevent this water from flowing in the direction of Kampen. The Kampereiland is protected by dike trajectory 225 and a part of this dike trajectory has been made resistant to the overflow of water. According to new insights, the crest of this dike section is too high and the Kampereiland inundates less frequent. It is also unclear whether inundating the Kampereiland leads to a water level reduction at Kampen and what the possible consequences are for surrounding primary dikes. The Kamperzeedijk is one of these surrounding primary dike trajectories and protects the city IJsselmuiden.

The influence of the crest height of this overflow resistant part on the water levels at Kampen and at IJsselmuiden is investigated. This is done by creating a python model which describes the hydrodynamic processes by using existing WAQUA computations as data input. From these data, a storm is simulated to compute the volume of water flowing into the Kampereiland. The influence on the water levels at Kampen and at the Kamperzeedijk is evaluated for multiple crest heights of the overflow resistant dike section. Eventually, these water levels are processed with a statistical model to compute multiple water frequency lines for each location and observed crest height.

The results from the model show that the current crest height causes Kampereiland to inundate during a 1/2,000 event, which is in line with the expectations. The results also show that a higher crest height leads to increased maximum water levels at the Kamperzeedijk and to lower maximum water levels at Kampen. Opposite effects are observed for lower crest heights. The water levels in front of the overflow resistant dike section remain unaffected. The return periods for overflow at Kampen and IJsselmuiden are derived by comparing the water frequency lines to their individual crest heights. These are shown in Table 1.

It is concluded that the inundation of the Kampereiland does not immediately lead to a load increase in front of the Kamperzeedijk, but a delay is observed. This delay is the result of the storage capacity of the Kampereiland. As soon as water from the Kampereiland flows into the Ganzendiep, the loads rapidly increase. Furthermore, concluded is that the Kampereiland is capable of reducing the water levels at Kampen.