It's not as simple as being pushed away from ploughing - I expect arable land is still ploughed for each crop that requires it, but where land does not support arable farming (ie hilly or small fields) the next option is sheep or winter crops for stock - around here silage. This is just three or four cuts of grass, needs fertilizer and slurry. Farming has changed so much around here, no cows to be seen, just wacky races of silage cropping and slurry spreading - so yes, runoff is much different, maybe due to less ploughed land, but the silage grass is much less dense as well, with loads of gaps between the swards.The B****y lot of them!
There has been talk of creating storm dams to hold back water, but the EU habitats directives would make that a difficult one.