Billed as maybe the tallest known beaver dam in the world, "Helm's Deep" in Voyageurs National Park is 11-13ft (3.4-4.0m) tall, depending on where you measure it from.

A short thread about big beaver dams.

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Even from a distance it is impressive. I'm 6'6" (1.98m) for scale.

There are likely other dams out there that are taller, but I've yet to encounter one up close.

There are basically full 15'+ tall trees stacked in here, which is unusual, to say the least!

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Every time I come around the last corner before the first glimpse of Helm's Deep dam comes into view, I always feel like Obi Wan Kenobi when he sees the Death Star for the first time.

"That's no moon....It's a space station!"

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And why "Helm's Deep"?

Helm's Deep is the castle/stronghold used to make a last stand against an invading army in Tolkien's "The Two Towers". Replace orcs with beavers and the resemblance is clear.

Also, no, I don't live in my mom's basement. Why do you ask?

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But I digress...

Typically, such large dams are multi-generational efforts. Doesn't necessarily mean constant occupation of the pond, as they can go "dormant" for periods only to be later reoccupied by smart beavers wanting to rehab old dam rather than start a new one.

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And what about long dams? The current Official Guinness Record Holder is 2,788 ft (850m) long, in Wood Buffalo National Park, Canada (see pic below). Lots of interesting press reports when this was discovered in 2007 via air photos and again when visited in person in 2014.

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We've measured lots of them in the 300-500m range in Minnesota and nearby Ontario, all typically in really flat, boggy terrain where the only way to store water is not by building tall dams upwards, but by building short dams sideways.

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Perhaps nothing is more symbolic of the unfailing work ethic of beavers than the existence of these monoliths. The beavers that built these are not bigger, stronger, faster, or more abundant than beavers that build smaller ones. They just keep workin'!

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@ben_a_goldfarb wrote a great piece in the StarTribune in July 2019 on his visit to see Helm's Deep dam and other wonders of the Castoropia that is Voyageurs National Park. http://www.startribune.com/voyageurs-national-park-is-the-epicenter-of-beavers-spectacular-handiwork/511910332/

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My guess is there are others out there who've seen some tall beaver dams in their neck o' the woods or on their travels?

Share a pic, location, and any measurements in the comments, or DM me. I am compiling some info for a book chapter.

Thanks in advance!