It works well
I had a plot down the back that was heavy clay and 4 to 6 inches of water would sit, for sometimes weeks.
A neighbour had cut down some small trees (2-3 inch) which I stacked lengthwise in a keyhole shape about 1 foot high in the wet patch.
After topping it off with few bales of lucerne hay and cow poo making an organic compost lasagne for the worms and other biologicals that love the stuff.
2 years later i have a garden that needs little water as it has its own reserve topped up every time it rains.
The biggest problem i have had is grass invasion because of the moisture reserve.
