It does look rather drastic Paul.
It would be interesting to know the rationale behind the felling, I’m struggling to understand how could be justified in terms of flood prevention. From a conservation perspective the only justification would be if the felling was to create / maintain an open floodplain landscape for the benefit of ground nesting birds (lapwing, curlew, snipe, skylark etc.), species which prefer open aspect landscapes free from ‘predator perches’’. This type of habitat management isn't undertaken lightly and usually after extensive survey. I don’t know the area in question –but from a cursory look at a map I think it unlikely that this would be the reason.
I suggest you contact your local Forestry Commission office(mailto:southeast.fce@forestry.gsi.gov.uk) to enquire if this work was granted a Felling Licence or indeed if one was applied for which is a legal requirement. The local Woodlands Officer should be able to advise you on this and provide the justification behind the felling licence application.
In the unlikely event that the FC aren’t forthcoming on this (they are usually very helpful in my experience), then you can submit an FOI Act request as they are a publically accountable body and this information is in the public interest.
A Felling Licence is required if >5 cubic metre of timber is felled per calendar quarter – judging by the diameter of the stumps on your picture and the fact that a two mile stretch has been felled then I’d suggest that well over 5 cubic metres has been felled. An exception to this would be the felling of trees that have the following diameters when measured 1.3m from the ground:
◦8 cm or less
◦10 cm or less for thinning’s
◦15cm or less for cutting coppice
http://www.forestry.gov.uk/pdf/TimberVolumeCalculator.pdf/$FILE/TimberVolumeCalculator.pdf
Usually if a Felling Licence is granted then some form of mitigation is required such as compensatory planting / restocking. See here for more info:
Felling Licences (England)
Judging from the stump on the left of frame, if the intention was to coppice then they haven’t done a particularly good job as the height of cut should be much lower. Nor would it be considered good practice to coppice the entire length.
The good news is that judging from your picture, they stumps haven’t been treated with herbicide (usually a blue or green staining is present on the stump) so the willow should grow back relatively quickly.