I’m talking about the controversial Santa Engracia dam in Pamplona. And from my own particular technical point of view, I enter the subject to see if I can shed some light on the numerous views expressed about its restoration or removal. And I do this after attending the municipal forum held in Civivox in the Rochapea neighborhood on October 25th, and was able to listen to them question how this dam poses a “serious” problem with the effects of flooding in that neighborhood. Having a small weir 2 meters high, for me, creates more advantage for the development of the fauna, rather than inconvenience, due to the level created.
Am I saying that such a dam does not cause a head loss by hindering the passage of the river? Of course not. Any interference on a channel does this. What I will try to point out is that this construction and other existing dams have had no greater impact on the level of intermediate locations from flooding than the old bridges (read San Pedro, Curtidores, Magdalena bridge or bridge). itself). de Santa Engracia) is located along Pamplona, passing through the most critical flood-related areas. Do we have to demolish them too? We would never do that, would we? They represent a historical legacy of the city that must be defended. So, what is the labor in that historic weir from the 13th century? You see, the biggest head loss in river beds that raises its level in floods lies in the accumulation of sediment in the water vein and even more (I dare) the zero cleanness of its shores during cleaning. The “intemerata” that those who have to assume their responsibilities (CHE) have neglected for years. There are no dams or bridges that pose a greater problem for this purpose. Am I saying that river banks should be left completely barren? Not even remotely. We all like to walk, thinking of nature living under the shadows. Before emphasizing infrastructures to protect, proceed to “clearing riverbeds” (their materials are in notable use for many construction work problems) and leveling “islands” on behalf of CHE, so that only sediment is removed, which is the push/drag of the next water level ends with elsewhere-) and removes all bushes and dead trees – nothing more than that stop and take a walk to see the shores that hold/accumulate any remnants that form true side dams for the pass (removed only when a new flood carries them to another spot) Water. Cleaning the banks, removing the unnecessary, leaving the trees healthy and healthy, with the lower branches pruned at the appropriate height, preserves the ecosystem and avoids real obstacles other than to give an “admirable” view of the river and the ubiquitous “manure dumps”.
And having said that, (as I’ve said before on that forum and in other posts) to point out the final effects of the so-called “historical flood” in relation to the Rochapea neighborhood, with direct and real knowledge of the cause. (December 2021) occurred intensely to a certain extent and occurred with the plumbing installation (with the overflow of the roads and the height in them) formed by the combination of continuous rains. The level of the river did not reach the roads and floods and conditions occurred. Can such conditions be mitigated/prevented to some degree? Yes if you want.
Javier M. Elizondo Osés, consultant and trainer in the field of water
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