From the archive: Great rivers, great influence

Background story on the high tide at the start of the route in mid-February. Photo: aerial view of the Waal near Winssen on 26 July 2004 (water level 9.00 meter +NAP at Lobith)

The catchment area of the Waal near Nijmegen is currently 10 times smaller than the original one. Yet the primal force of our great rivers has not yet been tamed. Every now and then, this sleeping giant comes to life and the water rises to unprecedented heights by up to 2 meters per day. Giving space to this natural phenomenon is the chosen answer of Rijkswaterstaat near Nijmegen near Lent. Since the extremely high water levels of 1993 and 1995, projects have been started at various places along the major rivers that have a major impact on the landscape.

While walking through the Stadswaard or floodplains near Beuningen, you can not only see the effects on the landscape of the river-widening measures. Every now and then, de Waal ‘shows his teeth’. For example, during a small high tide wave, in mid-February 2016. Below you will find more information about that high water wave, the water levels and about the influence of the interventions that should protect us from future disasters.

High tide wave, mid-February 2016

On 13 February 2016, the high water wave on the Rhine near Lobith reached a height of 12.95 metres above sea level. That is a position that is reached almost every year and is certainly no reason to panic. The groynes will then be about one metre under water and only the lowest (unquayed) parts of the Stadswaard and Bison Bay will disappear under water. Still, that is more than 5 meters more than the level that is considered “normal” for the river. Then it’s a serious pair of wet feet.

The above-mentioned summit was reached after a period in which the river had risen 25 cm per day. That is not extreme either, because there are known high tide waves where the water rose more than 2 meters per day!

After reading these numbers, you may think: “so that high tide didn’t really mean anything”. Then it might be good to realize that, at the time of the peak, no less than 5000 m3 of water per second flowed through the river. A water column of 500 meters wide and 10 meters high. You don’t want that flowing down your street, it seems to me.

During the high tide wave of February 2016, only the lowest parts of the Stadswaard were under water.

Sleeping Giant

For large parts of the year, not much of the untamed primal power of the river can be seen. It flows steadily through endless lowlands to the sea and at an appropriate distance the winter dikes wait for their turn to turn the water.

During a summer walk through the Winssensche waarden or outlands near Beuningen, it is therefore difficult to imagine the power that the Waal can develop. There is a good chance that during such a walk, the river will flow within the summer bed. With a flow velocity that is suitable for bridging about 8.5 meters of altitude difference over a distance of 150 kilometers. This is the distance between the point where it enters the Netherlands (near Lobith) and where it flows into the sea (at the Haringvliet locks).

At extremely low water levels, the river at Lobith drops below 7 meters and locally less than 2 meters of water will flow through the river. How different is it at high tide? During the highest level in recent decades (that of 1 February 1995) there was almost 10 metres more water in the river. The water is then up to the top of the dike and the river is usually 2.5 km wide! According to Rijkswaterstaat technicians, more than 11,000 m3 of water flows through the river every second. It is therefore fair to speak of a ‘sleeping giant’. A primal force that you’d better make room for.

High water on the river is at the Plaat van Ewijk with the A50 in the background. Picture taken on March 20, 2001 (stand of the 14.15 meters in Lobith).

Room for the river

The above facts and figures make it clear that our major rivers must be treated with respect. To prevent future disasters, the Dutch government has therefore initiated a process to make room for the river. In this context, side channels are constructed, floodplains are excavated and even dikes are rebuilt.

A good example of such a project is located opposite the city centre of Nijmegen. At the height of the Waal bridges in Nijmegen, there was a bottleneck that caused backwater in the river. As part of this project, known as Veur Lent, the Waaldijk has been set back 350 metres and a secondary trench has been dug. The work was completed at the end of 2015 and during the high water wave of February 2016, the channel flowed along for the first time.

Near Nijmegen, the winter dike has been set back 350 metres at Lent and a secondary trench has been dug.

Photo above: April 21, 2009 for the work. Photo below (Toine Peereboom): 13 February 2016 with a flowing side channel.

For more information see:

www.waterpeilen.nl (up-to-date information on water levels)

www.ruimtevoorderivier.nl (information on the works along the major rivers)