Hi Group
My soakaway consists of a hole about two feet deep and two feet in diameter dug at the lowest edge of my lawn. Two hydrangeas planted opposite each other either side of the hole, these have now grown to cover the hole. They drink all the water they can get and the hole provides temporary storage in times of heavy rain storms. It works is all I can say! The climbing hydrangea is now a few inches short of the apex of the roof on my two story semi-detached. Obviously not a good idea if you dont like these plants
Alan