There is no option but to divert the water into the Goyt, it's going to have to go into there one way or another.
They are currently trying to lower the levels in the reservoir, by diverting the water into the Goyt.
It needs to be done in a controlled manner. If that dam bursts, it will take out the whole of Whaley Bridge and flood into the Goyt anyway, but taking everything in it's path. Whaley Bridge and any bridges over the Goyt, everything!