We have a drainage / flooding problem where lots of water passes through our garden, from the higher house on our right to the lower house on our left.
I want to put in a raised garden, which has a "base", "under-bed" that allows the water to pass through it, or even to stay in it, but with a good soil layer on top of it, in which the plants grow.
What material should I use? Clay Pebbles? Straw? Mulch? What can be cheap and workable? Is this even a good idea?