This is the EA flood map for Carlisle.
Note the narrow end of the flooding at the disused railway viaduct downstream of town.
Just upstream of this there used to be a power station that has been recently demolished. Did any rubble end up in the river? There is certainly something blocking the river just above and below the viaduct.
Half of the bridge is blocked and needs clearing.
This is not allowed by the Berne Convention - see “Why Britain is flooding” on the Home page.
The River Eden is tidal 5km downstream without a tidal sluice and may have some effect.
The river through town and under the A7 bridge is full of gravel as usual
I will work out the rest of the Carlisle story ASAP, please check later.