🚀 go-pugleaf

In article <717d0s$4d$1@news.NERO.NET>,
Dave Rabinowitz <daver@holmes.ECE.ORST.EDU> wrote:
>>Moving water will pick up sediment. If it doesn't pick it up from the
>>protected bank, it will pick it up from the next available place. This
>
>This claim is not obvious to me.  Could you explain the physics behind it?
>It's not like sediment dissolves in water until saturation.

You have a river moving with enough energy to pick up sediment. For a
certain length of run, it is prevented from picking any up. Ten feet
further along, it can pick it up. What physical process do you imagine
will prevent the same river, flowing at the same speed, from picking up
the sediment that is unprotected when it would have picked up the
protected sediment?

The problem is, the sediment that it would have picked up from the now
protected bank will not be deposited ten feet down the river. Ten feet
down the river you have erosion. So you protect that. Then you have to
protect ten feet further along.

Then you have to go back upstream and extend the protection. The
leading edge of the protected bank is now a perturbation to the flow
which will increase the turbulence and increase the erosion of the
unprotected bank.