Oh dear, "you cannot mess about with the natural flow of a river...."

The "natural flow" has already been "messed about with"! Umpteen bridges have arches or other foundation in the river bed and many hold debris during times of heavy flow contributing to flooding upstream of the obstructions. Weirs exist in many places and have done for a very long time. However, they're fixed, ie they're always there and remain the same height.

What do you propose to do to "retain the natural characteristics of a river"? Demolish all the bridges and weirs? With the weirs gone you'd soon see how low a river would get during Summer"

During Summer or times when rainfall is low, any fine silt travelling downstream and possibly retained by a weir would surely be washed away during times of heavy rainfall when moveable weirs were lowered?

I suppose those who oppose deepening a river and improving the flow during times of heavy rainfall are also those in favour of "messing about" with the flow of tributaries by re-introducing Beavers?

As to the lower reaches of the Severn, wasn't that "messed about with" by deepening to allow boats better access up the river?

There comes a time when people just have to make their minds up, do they want to retain the "natural flow of a river" and put up with associated flooding or try to do something about it.