Flood memory and historical marks of high waters

Contributed by Maria-Helena Ramos (Irstea, France)

Last year, the Hepex Portal published a blog post by Richard Davies from floodlist.com about the UK and Ireland floods in December 2015 and January 2016. When navigating through the floodlist website, I found a page dedicated to flood and high water marks (here).

I have always found these marks indicating the level reached by the waters of a river (or any other waterbody) after a flood event to be fascinating. It is not only because of their hydrological importance or contribution to the analysis of extreme events. I like the “memorial” role they play for nature. They remind us that on those particular occasions that river was flooding or reaching levels that were remarkable for people living in the surroundings.

A recent paper (Sustainable flood memory: Remembering as resilience) has discussed the importance of keeping flood memory alive: “Flood marks, flood gauges, early warning systems (mediated by television, radio and online), public photographs, videos and news reports are the mnemonic practices that ensure that floods cannot be entirely erased from lived memory.” Interestingly, the authors mention an “unexpected materialization” of flood memory from a person that “kept a decanter on her table, which contained (after over 5 years) a volume of turbid water from when the flood had entered her property.” (check the nice photo illustrating it in the paper).

The authors’ study indicate that “Personal memory is a finite resource of potentially high-energy engagement. Forgetting how to live with flooding reveals a political economy of mismanaging memory (as much as water) that drives vulnerability.” (more about this topic can be seen here too).

The Zouave in Paris as a landmark for floods in the Seine River

Last year in France, we had severe flooding in the Seine and Loire river basins in late May-early June. A heavy rainfall event reached the northern part of France and was characterized by persistent and strong rain intensities. According to Météo-France, May 2016 was the rainiest month of May in northeast France since 1959. In some areas, rain fell over soils that were already wet due to previous rainfalls over the month, which contributed to severe flooding, mainly over the Upper and Middle Seine river basin and in several tributaries of the Middle Loire river basin.

In Paris, the increasing levels of the Seine River were followed closely during the event, due to its impact on commercial activities in the banks and the public underground transportation system. In addition, the catastrophic consequences of flooding of the Seine River also include the risk of flooding buildings such as the Orsay, Louvre and Grand Palais museums or the National Museum of Natural History. If you walk along the Seine in Paris, you will see how close these and many others monuments are to the river.

But let’s come back to the flood marks. As you probably know, the most famous “landmark” for the floods in the Seine River in Paris is the “Zouave du Pont d’Alma”. Situated at the Alma bridge (here), this statue of the artist Georges Diebolt, built in 1856, is an indicator (although not really too accurate, as  discussed in an article of Le Monde on 3 June 2016) of the severity of a flood event: in June 2016 waters went up to the hips (6.10 m), as in 1982 (6.18 m); in 1924, up to the waist (7.30 m); and in 1910, up to the shoulders (8.62 m). It is often considered that “floods are occurring in the Seine river when the statue has its feet in the water” (which starts at about 1.5 m, and can mean the beginning of trouble for many of the city’s inhabitants).

The Zouave is a famous mark in Paris and I’ve just found out that it even has a dedicated song, which you can listen here or read the lyrics (in French) here (thanks to the passionate French hydrologie.org association of hydrologists and my colleague Vazken Andréassian, a collector of hydrologic poems, as mentioned here).

But how to mark a flood?

Anecdotes aside, I want to come back to the flood and high water marks. It seems it is not so simple to mark a flood as one might think. I guess (or hope) no one was really there in person doing the mark when the flood occurred. This means that a flood mark needs to be searched for just after a flood, and here comes the importance of a good technique to do it in an effective way.

The U.S. Geological Survey recently published a manual with techniques and methods to identify and preserve high-water mark data (here). They say that “searching for recent high-water marks requires an eye for detail that is best developed through field practice.” It is a well-illustrated guide and tips are included to help you collect data. These tips are  (check out page 44): Safety first; Respond quickly; Look up; Stand back; Visualize the flood; Hunt for hidden clues; Think ahead; When in doubt, collect more data.

I personally like the “Visualize the flood” tip, where you are advised to “imagine the water at the peak stage”. I think it can be a good exercise to put into practice (using our imagination) a lot of concepts we have learned about channel hydraulics, river water velocity, but also local vulnerability and flood exposure.

In France, we have a national database where you can add your photo and contribute to keeping the memory of floods (check here).

Do you have a similar one in your country? Would you like to tell us more about it?

Contact Hepex co-chairs and website administrators if you would like to propose a blog post telling a bit of the history of floods and flood marks in your city or country, or if you just want to post your best photo and share it with us!