Hugelkultur beds and winter freezing

Hello folks, I'm just beginning my permaculture journey and have recently become interested in Hugelkulture beds. I've been doing research for the past few days and I've run into a bit of a snag. First, I want to give a description of the situation and then I have a question.

I have a relatively small back yard hillside behind my house. The hill comes down and dead-ends in a concrete wall. In looking at the yard and thinking about installing a hugelkulture bed, it would seem to make sense to me that I would want one bed near to flush up against the concrete wall, with another one or two slightly higher up to "slow" the water coming down off the hillside above. I would of course be creating swails in front of each bed. I was also thinking to perhaps angle the two higher beds so they act like an old "donkey kong" level and trickle the water down amongst them. My worry and question is thus though. We have fairly cold winters here, I live on the northern panhandle of West Virginia about 45 minutes from Pittsburgh, PA. If the hugelkulture bed is storing large amounts of water, won't that freeze and expand during the winter? The reason I ask is, if I butt one bed up against that concrete wall, and it freezes and expands, it could break the wall given time. Should I be concerned about this or would any freezing expansion be absorbed by the soil without issue?

Thanks much for your consideration and time.

well I'm not tooooo familiar with West Va..but do you really have a hard freezing problem there? IF SO..then anywhere your "water" stops..frost will also stop..

frost, like water, flows down hill, if it hits and object it will stop and settle in that area..and that will be what is called a "frost pocket" (you might want to search frost pockets online for more info).

Frost pockets can be death to any tenderish plants at all..

The best thing to do where there is any frost or freeze situation is to NOT have anything that will completely stop the flow, open the flow up so it won't just sink there. Recommendations are that fences have openings in them to allow frost to continue downhill and not to plant at the very bottom of any hill anything that is at all frost tender.

there are a lot of books and articles available that will instruct you on how to avoid frost pockets, make sure you are clear on that BEFORE building

Thank you, Brenda. I'd not heard the term "frost pocket" so I'll have to do some searching on that. Cheers to you!

It may perhaps be counteracted a bit by the heat generated by the wood rotting in the hugel bed

Adding a couple of large stones (dark colored) in the frost pocket or near vulnerable plants could help keep the area a little warmer during frosts.

As long as the cold air can flow around the bed in one direction or another, you shouldn't have too much problem with that.

Also keep in mind that, while it does stop the flow of cold air and water (because a frost pocket isn't just caused where water flow stops, but where the downhill flow of cold air stops) the concrete wall will also store heat, so it may completely counteract the frost pocket depending on the heat energy accumulated during the day. My thoughts- try it for a year and see what happens. I wouldn't worry much about damaging the wall because being at the bottom of a hill it is already collecting water. All you're doing is slowing down the flow, which may actually help. Freezing should only be a problem when water freezes and expands in confined spaces as well, like cracks, and since it can expand away from the wall as well it may not cause as much damage.

Thank you for all the fantastic responses, everyone. I finally decided to bite the bullet and began cutting out the first bed today. Took a couple pictures if folks are interested. This is my first time out with all this so bear with me.

been a few months... i know from experience hand digging hugel beds (especially if they are tall, steep beds) is hard work, but are there any more pics of your project?

It's past end of the growing season so not much to show. The bed is covered with a layer of leaves and end-of-season cut grass. All in all it did quite well. The nitrogen sucking effect of the wood was a bit of a problem and as a result several things would not grow well in it, however I got about 15lb. of cucumbers, 10lbs. of tomatoes and would have had a good haul of watermelon had the deer not decided to browse all the fruiting bodies off the vines. Next year I will put some kind of barrier so the deer can't get to it. The bed is 3' wide and 12' long. It's mounded up about 8" above ground level. I would have gone higher but this is on a hillside and I was worried about erosion.

A couple lessons I learned in the process.

1. When putting a hugelbed on a hillside, it's probably better to do a hugel-swale hybrid. Map out your contour lines, place your brush/wood on the downhill side of the contour map, then mound up your dirt from the swale on it, then heavily mulch the pit of the swale to pre-slow the water. Also, make sure your "lip" of your swale is nice and graduated. Some rocks/gravel along the upper edge of the pit will help to slow the water as it runs down the hill to your swale.
2. Use mulch that won't compact on you. I used cut straw and it ended up shedding water away from the bed than to it. Next time around I'll source some actual straw bales or just wait until the grass gets long enough to chop off and throw on top.
3. When working with sandy soil, add your organic matter AS you are putting the sand/dirt back. My soil had very little organic content and I had to come back later and tear it back up and mix in leaves/straw/compost/etc in order to get some sort of nutrient and water retention. (It was dumping water out as fast as it was coming in.)

All in all it was a great experience. I learned tons from it, both in what to do and what not to do.

Edit: I wanted to add, I had thrown the seeds for a ton of other things into the bed but I think most of them went too deep when I came back later and dug up the top 10 inches to mix in organic matter. What did end up coming up mostly got browsed by the deer. My sunflowers, collard greens and cauliflower were their particular favorites.