What are expansion tanks and why they are little loved (in Emilia-Romagna)
What are they for, how are they made and how much do they cost? The expansion tanks are essential to avoid disasters such as the one underway in Emilia-Romagna and yet people are reluctant to build them… Facts, numbers and comments
Designed to contain the rivers and prevent them from overflowing, the debated expansion tanks are at the center of the debate on what has not been done and what could have been done to avoid the disaster that is engulfing Emilia-Romagna following the floods , which they flooded 23 streams and caused over 50 floods.
But what are they and why aren't there enough?
WHAT ARE EXPANSION BOXES
Expansion tanks are artificial containment basins that allow the water of rivers to be temporarily "parked" when they reach full water and then made to flow out in a controlled way, avoiding overflowing.
In fact, when a certain level of the watercourse is reached, this hydraulic work foresees that a part of the flow of the river is diverted into the artificial "expansion" basin so that the flow of the river is attenuated and a flood does not occur.
HOW THEY ARE MADE
The expansion tanks are made up of large artificial tanks equipped with controlled drainage systems, designed precisely to lighten the flood, flow rate and pressure of the water.
There are two types: in-line checkouts and side checkouts (also called branch checkouts). The former are positioned inside the river and include a crossbar, which blocks and slows down the flow of the river, and small openings, called lights, which are used to drain the water, as happens with dams. The latter are, on the other hand, positioned next to the river and allow the stream to flow automatically in the event of a flood. When the river level is low, no water enters, while when it reaches the threshold, the water enters, in a controlled manner, in special areas where it is collected.
BECAUSE THERE ARE EXPANSION TANK IN EMILIA BUT NOT IN ROMAGNA
As we read in an in-depth study by the Agi news agency, the expansion banks are present in Emilia but not in Romagna. They are found, in fact, on the Panaro, on the Secchia, on the Crostolo, on the Lenza and on the Parma torrent.
The reason for this lack of homogeneity, according to a document from the Italian Hydrotechnical Association reported by Wired , lies in the fact that Romagna has historically been subject to fewer floods than Emilia, where the first expansion tanks were installed "already from the end of the seventies, on the initiative of the Po interregional agency following the floods of 1973”.
Emilia-Romagna, underlined the National Quotidiano , received 190 million euros between 2015 and 2022 to build 23 of these, however, only 12 of these are operating at full capacity, 2 others are working in part, 9 are waiting the end of the works and 2 are still to be financed.
THE EXCEPTION IS ALREADY THE NORMALITY
Unfortunately, however, having been designed to deal with exceptional events – "two hundred years", civil engineering professor Armando Brath, of the University of Bologna, an expert on expansion tanks, told Agi – they are not sufficient for violent and close-quarters episodes such as those which occurred from 1 to 4 and then from 15 May.
This is why they should be reviewed in the light of current climate change because, as Barth explained, "what we thought was thirty years [to intervene] may have instead become 15. The times for reproposing emergency events have shortened . More frequent and also more intense”.
WHY DON'T LIKE EXPANSION BOXES VERY MUCH
But the expansion tanks are not only out of date, they also enjoy little popularity among both Italians and administrators. According to Barth, in fact, many people are affected by Nimby syndrome ( Not in my backyard ), or "it is done everywhere but not in my house", but politics also has its responsibilities.
Since these are very cumbersome and very expensive works, not so much for the work itself but for the expropriation of the necessary land, and which do not even give an immediate political return, the administrators are reluctant to embark on their construction.
To get an idea, says Barth, "they can cost in the order of several tens of millions of euros, but if the thing is important even a few hundred".
This is a machine translation from Italian language of a post published on Start Magazine at the URL https://www.startmag.it/energia/cosa-sono-le-casse-di-espansione-e-perche-sono-poco-amate-in-emilia-romagna/ on Fri, 19 May 2023 09:52:33 +0000.