If you want to drain an area, you can dig a trench and fill with clean stone
chippings, or lay a land-drain pipe. Lead the trench downhill, to an area
where it doesn't matter. It's preferable to pipe into a manhole or stream.

Since it sounds as though it is a bit of reclamation I reckon the
best part of the enterprise will be watching the succession of weeds
which manage to get dominance.

"Oh look! That one's arrived. Well if that's enjoying itself, I
know another which will enjoy it just as much and it is ,,, erm ,,, a
little prettier. Sorry!..."

Hussein