The first stage channel, about 20 m wide in the middle, continuously filled with flowing water, has the sloping sides of the second stage channel, between 40 m and 250 m wide, either side.
This second stage channel is only occupied at peak flood time. This is an experiment; has not been tried before in the UK. Weedy species will colonise, but they will be Indian (Himalayan) balsam, and unpalatable hybrid sedges. In view of the lack of maintenance by the EA recently, which has created many of the flooding problems can we expect them to maintain the secondary channel so that water continues to flow along it?
The formation of a new channel will empty the old ones (Hinksey, much of Bulstake and Seacourt Streams) creating anaerobic swamps and killing all the fish and wildlife characteristic of a healthy channel. This must be set against any eventual gain of wildlife.
Fake News
It is fake news for the EA to claim that the destruction of up to 4,000 trees, with its effects on bats, birds, insects, bryophytes, lichens, and so on will produce a net increase in wildlife. It takes 60-80 years to create the full biodiversity of a newly created habitat from scratch (references can be provided), and that goes for freshwater, swamps and woodland as well as MG4 flood meadows.
No previous example
The EA have been forced to use the TVERC ‘biodiversity calculator’ which is based on area of potential habitat rather than species richness or diversity. There has been no case in the UK of a flood meadow being created from ordinary grassland (e.g.MG5), because it requires the purchase of land which is occasionally flooded, and the expensive annual regime of an annual hay cut followed by aftermath grazing.
Hinksey Meadow has been a flood meadow for 1000 years and is so much more diverse than Iffley Meads SSSI (BBOWT). There are 199 ha of MG4a vegetation left in Britain and 7 ha is on that site, which the channel and its construction is due to devastate; the drying out caused by this channel may well put paid to the rest. By suggesting that it can be replaced elsewhere at a stoke, the EA either displays considerable ignorance or a cynical disregard for biodiversity and the public.
Dr Tim King