Two or three possiblities spring to mind. First (and please don't yell) did you lay a water permeable membrane? second, if it was a fine pored membrane, then the pores might have become clogged with the bark as it has disintegrated, third the ground underneath might be saturated with water and unable to take more away, especially if it is a play or patio area where use will compact the underlying soil and make drainage worse. Solutions? either way improve the drainage of the underlying soil, if its either of the first two, also replace your membrane. My garden has become more liable to flood a t one end due to neighbours paving over areas of theirs and leaving less overall natural soakaway. There's not a lot you can do about that it but it might help you to understand what has happened. Generally, also this has been a wetter winter. hope this helps