The book that I have most enjoyed whilst researching the history is Jeremy Purseglove's Taming the Flood. This was published in 1988 and is particularly useful in tracing the upsurge of environmental awareness in the 1970s and 1980s, when it became apparent that the UK's wetlands were being destroyed in order to create more farmland, most of which was simply used to add to the EU grain surplus, the butter mountain and the milk lake. Purseglove, who started out working for the Severn-Trent Water Authority, ended up presenting a series of programmes on Channel Four. Taming the Flood won a Conservation Book Prize in 1988, but can now be bought second hand for practically nothing.
I particularly like this passage:
"The best way to understand the potential conflict is to look not at a photograph, but at Millais' painting of the drowning Ophelia. Engineers always enjoy this particular illustration of their dilemma, since they like to imagine that the drowning maiden, complete with her posy of botanical specimens, is the lady from the local naturalists' trust, flung into the river after a particularly exasperating altercation over the conflicting aims of river management!
This is scarcely surprising, since all the habitats which the artist portrays so lovingly would be certain to give modern river engineers some headaches.
"To observe the riverine setting for his painting, Millais set up his easel near Ewell in Surrey, beside the Hog's Mill River, where he was much beleaguered by swans and midges. He accurately depicts flood-wrack on the bank at the right-hand corner of the painting. The pollard willow, complete with germinating seedlings in its crown and a robin perched on it, leans perilously out into the stream. Left there for long, it will undoubtedly fall into the river and cause a blockage. The dogrose, splashed over with white July flowers and creating welcome cover under which birds and animals can scuttle for safety, will be sure to catch all the dead logs and other debris to come bobbing down in the next winter flood, and make that blockage even worse. To the right of it is a vertical river cliff, whose unstable eroding surface has provided a fresh seedbed for the biennial teasel, but which is likely to continue to slip into the stream despite the binding roots of the purple loosestrife on its top. Beside Ophelia's head, the ever-invasive forget-me-not and tall clumps of branched bur reed, essential for the survival of many insects and fish, grow out into the stream, trapping silt and clogging the watercourse. Finally, to ensure a flash flood with the advent of August thunderstorms, the mossy webs of crowfoot floating in the foreground could raise the mean summer water level of the stream by as much as a metre. You can be sure that the Thames Water Authority would never allow the Hog's Mill River to get into such a dangerously picturesque state today."