Drainage trench?

[out in the cold]

That looks good mrgrower.

As AP suggested, a gravel base, fill with a land drain pipe and top up with some more gravel would be a good way of making sure you had runoff, assuming there was somewhere to actually take the water off to.

Are you able to arrange a fall across the depth of the site, so the water runs away from one end? That way it accomodates any heavy rainfall and deals with it, rather than simply becoming a long narrow pond at the bottom of your site

[mrgrower]

Thanks for the reply. The trench runs to the otter limit of the plot and on the other side is a bramble area to the train track so it is hoped it will run of into there.