New curves in the Dearne, in South Yorkshire, will create riffles and pools and different flows to encourage new species of fish, and lush plantlife.
It is an attempt to repair damage caused during the Industrial Revolution, when part of the river was engineered into a straight, narrow canal, and the environmental consequences were ignored.
Although the quality of the water has gradually improved, the return of wildlife has been hampered because the Dearne was too straight.
Today, earthmovers are being used to bring back bends and allow the river to meander gently through the Dearne Valley, in a pounds 400,000 restoration programme led by the Environment Agency.
Its chief executive, Ed Gallagher, said: "The historical methods of forcing the river into long, straight channels to remove water quickly during times of flooding cost the Dearne dearly in lost wildlife.
"The agency's work to replace the bends in the River Dearne recreates its natural state."
The first phase of the three-stage river redevelopment has already been completed, with the second to be finished this month, and the third by June.
Chris Firth, the area fisheries officer, said he hoped to see more varieties of fish thriving, including roach, dace, chub, tench, pike and bream. "The new gravel banks are invaluable to wildlife because they allow fish to lay their eggs."Reuse content