Oehler Style - rain catchment?

Mike, here's a question for you:
Have you any experience with rain catchment on your structures?

When I built my underground house, I stuck with your design up until the roof part, as I live in a very dry area, and with no well (or money for one), rain catchment is a must.  So, instead of an earth roof, ours is a concrete vault that is insulated with standard materials.  It is not the best compromise in the world, but it works well.

I have considered many options, like an earth roof with a layer of metal on top, or concrete on top.  But none of my designs really solve the issue with grace, and they end up costing more in both labor and money than standard concrete roof systems. (vaults and domes)

I am wondering if their is a better system that allows for the low-cost approach of your earth roof design plus the practical side of catching the rain water.  Any thoughts?

Many thoughts, Velacreations. They all center around the sad fact that earthen roofs are not catchment roofs. On the Ridge house we are adding a balcony with a metal roof to catch water and the wing that goes off to the east will also have a metal roof, too. We are building a pond up there and the well water is contaminated so catchment is the way to go. We have also considered rolling out polyethylene on top of the earthen roof during rains and catching it that way.

So.... I live in Oregon, where it can rain a lot and water does move through earth all the time, unfortunately to pool in my backyard, but that's another story.

My question is, in places that get a lot of rain wouldn't the water move down the soil of a green-roof once the soil was saturated, and then couldn't it be directed/collected in some manner? 

I would be worried about over water-logging my green roof if I don't provide some kind of escape for the extra water during heavy rains.  I have pictured fine meshes at the base of the roof to hold back the soil while allowing moisture to escape.

What are your ideas on this?

Thanks

@Jami
I have seen people do layers of gravel and drainage pipe for green roofs to help with drainage.  I would suspect that the water would contain a lot of sediment, which would need to be filtered before storing in a cistern, but possibly doable!  I would think that this type of solution would work best in a wetter climate.

@Mike
Yeah, I realize these roofs are not really the best choice for rain catchment.  A rollout plastic layer is an interesting idea.

I guess something like a concrete or metal layer on top of everything is the best option.  It is a shame, because metal roofs are not nearly as beautiful as a nice bunch of plants on top!

I don't think you have read my books or seen the videos, Jami. I run the moisture off the roof onto or into solid earth on the downhill side. We considered at one time catching it down there in a sand filled basin of polyethlene but don't think we have enough rain for that here in N. Idaho.

No I haven't seen much Mike, as earth shelter or underground housing hasn't been on my radar.  But I've seen Paul's videos, which only give a gist and not the detail obviously in your book/CD's.

This is why I ask     to learn how you deal with extreme water, thanks.

Thanks ~ Vela I'll have to look into that.