Why the Sewers Canal Was Put on the Backburner

There aren't any locks in the sewers canal as opposed to something like a Panama canal, which is bloody full of them. So why did these engineers come back to Napoleon and say, hey, we need to put locks in because there's a difference in the sea levels? They just got it wrong. And so once again, the idea was abandoned. But the idea was such a powerful and such an alluring one that it didn't lay dormant for long.