Can waterways which are prone to flooding be dug deeper to help prevent flooding? Like just digging big trenches through the bed of the waterway?
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You mean dig trenches locally, or through the whole river system? If the whole system, that’s a lot of work to do and maintain, and ultimately you’d have to deal with the ocean coming in to backfill the trench you dig. And then you’d have to deal with sediment, etc…
If you mean locally, that wouldn’t work either because the flow would simply adjust to re-attain an equilibrium between the upstream and downstream flows. There wouldn’t be *no* change but you may actually end up with faster flows that do more damage.
Finally, why is this different from a dyke? Because a dyke only kicks in when the water level reaches it. It’s no interfering with the flow as it currently stands. A trench would change the flow conditions of the river under normal conditions, and then you’d have to think about how upstream and downstream conditions affect your trench, and vice versa.
These videos give you a sense of some of the flow changes that might happen if you dug out a trench. It also gives you some search terms if you’re still interested!
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