Eli5 – How do you build a dam?

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The recent dam collapse had me thinking how on earth do you build a dam? Huge river with loads of water – how do you even start without the water washing everything away? How do the workers manage to cope in such conditions?

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5 Answers

Anonymous 0 Comments

Often they divert the river. For example when the Hoover dam was build the first step was to create an artifical tunnel through the rock to divert the Colorado River. That left the dam sight dry allowing construction. When the dam was completed they sealed up the diversion and the resivoir behind the dam filled.

Anonymous 0 Comments

Typical is to go upstream from the desired dam location, and make a diversion around the area. Then build a simple dam (fairly small) called a coffer dam to force the river to flow through the diversion. This dries and exposes the final dam site for construction.

Anonymous 0 Comments

Check out this short (https://www.youtube.com/watch?v=n9Gy_1Ppw5U) on the Hoover Dam’s construction.

One thing to remember is that the lake behind a dam was not there before the dam. In other words – it’s a river that you are diverting, not a massive lake. Still a massive job as the Hoover video showed, but more doable than say 200 ft of water depth and pressure.

Anonymous 0 Comments

This video is about the current ongoing project of Site C in British Columbia Canada and I think it is worth watching for anyone who wants to get a general understanding of what goes into building a modern dam.

Anonymous 0 Comments

Usually places that have dams were just rivers, not lakes. So you let the river continue flowing under or around the dam until it’s done, then you finally close it off and fill up your new lake.