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!
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!