It's not just grass airfields that suffer this fate. I used to instruct at sandtoft, which like most of north lincolnshire should by rights be either underwater or marsh land! it only takes a reasonable downpour and the runway had two puddles across the full width (a staggering 18m i may add..
) about 18 inches deep in places! In fact the new grass taxiway/unlicenced grass (not in pooleys) is usually far more useable!