Nile Cataracts, a few questions

Saphroneth

Banned
Ooh, I've been mentioned as an expert witness. That feels strange...


Okay, first off - the nature of the cataracts. Roughly speaking, they're where the river runs over harder rock (either folded or basement) compared to the rest of the river. It's more resistant, and is also being uplifted in some cases, which is why it's not been eroded down.

Second off - their size. I'm not certain of this, I just had a quick look, but it seems like the upper cataracts at least are very large areas. Hundreds of km long, which is impractical to "dredge" as it were - especially as the rock is harder than average - and would be best obviated by a "dam" method - as used now, basically submerging the cataract area in an artificial lake.
Lower cataracts seem smaller (Second was nine miles long and had a drop of 60 feet, as per River War by that renowned WW2 Prime Minister Winston Churchill).

Now, there's been attempts in the past. One of them was in the 1000s AD and concerned the First Cataract. This is the one where an engineer boasted it could be done, went and had a look, gulped, and pretended to go mad so he wouldn't be executed.
Ultimately the Low Aswan dam was made in 1899-1902, and was then the largest engineering project in history. (It was then smaller than it is now.) It did include a navigation lock.


I think it may be technically feasible, however, to make a KIND of canal around a given small cataract - if you throw enough men at it! Specifically, you would have to dig out a smooth-gradient route around the entire cataract while the area is dry, potentially having to floor it with hard stone, and then dig through to reach the Nile above the cataract.
This does have a myriad of problems (the hard stone which makes the cataracts cataracty, the difficulty of judging what you want the navigation height to be, the need to include several dozen feet of freeboard above the nominal water height for the yearly floods)... ultimately, it may just be impossible in practice.
It's engineering on a scale out of all proportion to antiquity, really - at least, when you factor in the presence of a river which periodically rises by an average of nearly 50 feet!
 

GdwnsnHo

Banned
It's engineering on a scale out of all proportion to antiquity, really - at least, when you factor in the presence of a river which periodically rises by an average of nearly 50 feet!

I don't question anything else - I'll accept the upper cataracts may be too much - unless they somehow get really really good. But out of all proportion? Admittedly I'm comparing it to one of the greatest, but would it really be that much greater than the pyramids?
 

Saphroneth

Banned
I don't question anything else - I'll accept the upper cataracts may be too much - unless they somehow get really really good. But out of all proportion? Admittedly I'm comparing it to one of the greatest, but would it really be that much greater than the pyramids?

It would be a more "great" project, actually. The Pyramids are large, but really basic - they're almost literally just big piles of stone. Artificial hills.
Well-made artificial hills, it's true, but they're not required to be especially structurally complex. The construction is also under "ideal" conditions - a flat area of bedrock, basically a "clean sheet" site.

This canal, on the other hand, would entail digging out something dozens of feet deep and several miles (if not tens of miles) long through hard rock... and then connecting it up to the River Nile. And you don't have explosives, so you can't trigger the final excavation step after you've got everyone out of the way.
Imagine what that stage would be like. (It's made even worse by the flood level change, too.)

Compare to canal building projects in the 19th and 20th centuries. The Suez was "easy" - through sandstone - and was still immensely costly.
 
It would be a more "great" project, actually. The Pyramids are large, but really basic - they're almost literally just big piles of stone. Artificial hills.
Well-made artificial hills, it's true, but they're not required to be especially structurally complex. The construction is also under "ideal" conditions - a flat area of bedrock, basically a "clean sheet" site.

This canal, on the other hand, would entail digging out something dozens of feet deep and several miles (if not tens of miles) long through hard rock... and then connecting it up to the River Nile. And you don't have explosives, so you can't trigger the final excavation step after you've got everyone out of the way.
Imagine what that stage would be like. (It's made even worse by the flood level change, too.)

Compare to canal building projects in the 19th and 20th centuries. The Suez was "easy" - through sandstone - and was still immensely costly.

How would a canal to bypass the cataracts compare to the one connecting the Nile to the Red Sea? In terms of the scale of the project and difficulty of the engineering, construction, etc?
 
How would a canal to bypass the cataracts compare to the one connecting the Nile to the Red Sea? In terms of the scale of the project and difficulty of the engineering, construction, etc?

The 35 mile long Canal of the Pharaohs made use of a natural feature, a former dry course of the Nile to make the work easier. It was cut deeper through the sediments and sandstone of the Wadi Tumilat. Taking this and what Saphreneth had to say, one could almost guarantee that building a canal (with locks) through the upper cataracts in particular would have been a huge engineering project for the ancients. Much more difficult than the Canal of the Pharaohs.

Again, why would they want to do this when, 1.) they could navigate the cataracts during the flood season 2.) the 1st and 2nd cataracts going into Kush marked an often hostile border?
 

Saphroneth

Banned
How would a canal to bypass the cataracts compare to the one connecting the Nile to the Red Sea? In terms of the scale of the project and difficulty of the engineering, construction, etc?

The one connecting the Nile to the Red Sea was, as I understand it, using a pre-existing course; through soft rock (loosely consolidated sandstone, not granite or other basement rock); a largely flat path.
 
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