rainwater catchment/craters/rain gardens - sanity check my idea?

Okay, I think I have a plan which is a good thing since I have a guy with a Bobcat coming in a few days. It will be the last time a piece of heavy machinery will be in the yard. I need the guy to move all the cement stacked in the yard (removed from the upper property and will be used to build retaining walls/terraces on the slopes.) So I figured it he was going to come move the cement so they could build the terraces I could have him save hubby's back and dig me a few holes to catch the water. Rain will hit the yard from a couple of places, I have 6 downspouts on the house that we will run under the deck and out to the yard. The back part of the yard is sloped slightly toward the area where I want to add the rainwater catch basins. I want to do a pond, eventually, but I can't afford to do it now (will have to do the liner thing - no room for critters here.) But since we can't do the pond yet I am debating having the whole dug anyway and just make a very deep raingarden for now then, later, I can take out those plants and do the pond.

What I envision is everything going to the top hole (future pond #1 on picture) first, then overflowing from one to the next, eventually to the lowest level next to the fence. (It used to be a two level terrace but it is all straight lines and doesn't look natural.) That bottom level is flat and flooded very nicely last winter, then it tapers as it gets close to the gate and fence at the bottom of the property. There will be one last rain garden/crater/catchement on the side of the fence before anything can hit the storm drain.

But before I dig all these holes I need to bounce the ideas around and make sure I am not missing something important.

The deepest hole would be the pond one (3 feet? 4? ) Then the next two, maybe 12-18 inches, then 10-12 inches, then anything else can overflower to the lowest level.

While the guy is here I will have him help spread the piles of wood chips so I can start to lay out the greywater plan as well.

Attached are a couple of pictures, one of the space without my crummy markup and another marked up with some basic ideas.

Does it seem like I am heading in the right direction? I will have to decide on the shapes of the holes on the fly since I need the wood chips moved first. I am not sure how deep to make any of these. I need to also site them so the dog still has long, flat spaces to run. Would smaller but deeper catchments work as well or do they need the larger size to better distribute the water?

I hope some of this makes sense. Thanks in advance for any input.

Susan

A bunch of small basins can work as well as large ones and they fit between existing features better. Be sure to put the excavated soil on the downhill side, tamp it down so it won't erode, and have a spillway to the next basin. This might need to be reinforced with rocks if you get erosion, and according to Brad Lancaster is supposed to be 1/3 of the height of the berm, and twice as wide as the berm height. I think your planned basin depth is probably good - my hand-dug basins generally aren't that deep except where I excavate way down to fill with wood.

Make sure the sides of the pond aren't steep in case a critter or person falls in.

Thanks, Tyler. The only way I am going to be able to do these very deep is because we will have the equipment for the day. Otherwise, not so much.

Oh thanks for the information about the spillways. I wasn't sure how deep and wide to make them. I will be reinforcing the spillways and the lower sides of the berms with rocks.

I'm excited since the Bobcat guy said he will be here either this afternoon or tomorrow.