Flood markers

In addition, a flooding can also be caused by, for example, the breaching of a reservoir dam, rapidly melting snow, or deliberate inundation. The latter can occur for defensive purposes, as was the case with the New Dutch Water Line, or to cause extensive damage, such as the inundation of the Wieringermeer Polder at the end of the Second World War.

In many places where there has recently been a flooding, you can often still see how high the water rose, for example by looking at walls. In the case of an extreme flooding, a flood marker or benchmark is often placed in a wall or at another distinct location, from which the height of the flood can be read. For instance, during a short holiday to Porto in Portugal along the Douro River, I was surprised to suddenly see a number of flood markers on the doorpost of a port barrel storage facility, the highest of which, from a flooding in 1909, reached almost to the top of the doorpost. I have not been able to ascertain what this meant for the stored port.

In contrast to the situation in Porto, in an earlier contribution to Flevolands Geheugen regarding the situation at Coney Island in New York after Hurricane Sandy, I described how in America, precisely shortly after the flood, all its features had been removed.

In the past, flooding occurred regularly in the Netherlands. This is described, among others, in the standard work by Elisabeth Gottschalk, Storm surges and river floods in the Netherlands (Stormvloeden en rivieroverstromingen in Nederland). As far as I know, the first river flood recorded in historical sources was the breach of the Noorder Lekdijk in 1233. Since then, many cases of flooding and their consequences have been described in publications, as well as the subsequent measures.

Consequently, flood markers can be found in various locations in the Netherlands. An overview of the marks primarily related to flooding from the North Sea or the Zuiderzee can be found in the publication Historische stormvloedstanden by Jacob van Malde. In her book Van Amsterdams peil naar Europees referentie vlak, Petra van Dam states that, as far as is known, the oldest flood marker resulting from the 1552 flooding was placed in the Hoenwaardse Poort in Hattem. The gate has since then been demolished, however, and with it, this flooding marker has also disappeared.

In 2025, the flooding of 1825, two hundred years ago, was commemorated in various places in and around Kampen in the form of gatherings, exhibitions, and even a bicycle route. For instance, there was an excursion to Hasselt organized by the Association for the History of Water Management, as described in a previous contribution to Flevolands Geheugen. To commemorate the flooding, flood markers were placed at various locations, providing a clear insight into the height of the flooding.

Particularly since the flooding disaster of 1953, and certainly since the extreme river water levels in 1993 and 1995, flood protection in the Netherlands has improved significantly. Further improvements are being made within the framework of the High Water Protection Programmes. However, continuous adjustments and improvements remain necessary. Let us hope that the National government, the Delta Commissioner, and the Water Authorities remain sufficiently vigilant and are given the room to implement and manage the necessary measures, so that there will be little reason for additional flood markers in the future.