Thank you for that explanation Jay. We were blessed with a little rain yesterday. I've been rearranging rocks and flagstone in the area where we had our veggie garden for fifteen years. If my health holds I will continue playing around with permaculture  designs to try and hold rain water when we get it like yesterday. I can't wait to get outside and see if the swales I created for our Currents got enough rain to catch runoff. I hope I hope! One of my favorite things to do when it rains is go out and see where runoff goes and move it to where I want it to go if possible. Nothing like playing in the puddles to make a person feels like a kid again!
Brian

Thank you all so much for the information here on keyhole gardening. I had never heard of this concept before and it has completely changed the plans I had started to develop for our small suburban plot. I'm going to put keyhole garden beds everywhere!

One thing I'd like to ask though is how this would go on top of sand? This land was formerly covered with coastal scrub, and all of the topsoil in the areas I'll be gardening was cleared to make way for the build. Would I need to alter the process at all to work with a sandy base? The drainage will be extremely good but I'm worried that this will result in water and nutrients leaching out of the beds sooner.

Thanks for your help.

Ash Dalton wrote:... One thing I'd like to ask though is how this would go on top of sand? ...  Would I need to alter the process at all to work with a sandy base? The drainage will be extremely good but I'm worried that this will result in water and nutrients leaching out of the beds sooner.
Thanks for your help.

Probably this will work on top of sand. Just add a thick enough layer of topsoil / compost, and wood, branches, etc. on the sand. Maybe some of your plants will stretch their roots to, and even in, the sand. So slowly they'll ameliorate your soil!
My garden has a very sandy base too. And I even build 'hugelkultur'-beds on top of pavement!

My soil is clay, not sand, but because we are in a drought the ability to hold water was vital this year to reduce the need for constant watering. The soil that held water the best was about 50% soil and 50% weeds: where the weeds were badly mixed with the soil the weeds got soggy enough to make problems with the roots of the plants.

If rotting weeds hold water that well, perhaps they could hold water in your sandy soil as well. But, you might try mixing them in better instead of just dropping them in the way that I sometimes did. I had no problems with the parts that were better mixed in with the soil

Here's an updated photo.

I'm watering it with about a litre of water in the centre bin about twice a week.  Most of the plants there are started as transplants, so they got a bit of water when they went in.

Not bad results for so little water. 

Just looking at the weaving has me on-board I have to do at least one of those.