experience with long term maintenance of raised beds on contour?

I manage a fairly large (for an urban setting) community garden and orchard. We are about to help a group develop the last section of our plot and it will be on a hillside that is more like a gentle slope than a steep angle so we have chosen to go with beds on contour. The beds will be a little over 60 feet long (18 meters) and 3 feet wide (1 meter) and there will likely be around 8 of these once we finish construction. We are in the southeast United States in North Carolina and receive and average of 42 inches (106 cm) of rain each year.

There will be no check logs or anything else holding the soil back so I'm just a little worried that even though it is not a steep hill that we may encounter some issues during downpours. While I have done several swales with planting beds and small scale contour projects this will be the largest and longest project so I'm wondering if there are any folks out there with any long term experience with the maintenance with this design. We will also be using organic, un-dyed fabric scraps as part of our bed makeup (on the bottom) as we next to a local clothing company that has loads of these scraps and has proven to be a time tested soil builder, weed suppressant, and water retainer so the thought is that with the contour done properly using our laser level and the addition of scraps we should be slowing the water enough to avoid trouble, but you know, I just don't know. I've reviewed the old threads dating back 6 years but no mention of long term maintenance once installed.

Thanks y'all,

David Myers
www.blackdiamondgso.com

I am in a similar situation to you.  I am looking to do some large hugelkultur beds in mountainous area in south western North Carolina.  There is a caution that is given with any hugel bed, and that is building them on the slope.  The one thing that they excel in, is holding water.  This then becomes a great stress to it's durability on a slope.  Have you decided completely against check logs?  I am planning to drive some stakes in on the downhill side of my hugel beds, and I wonder why you would bypass this safety essential?  I know that they aren't ordinarily used, but I would experiment using the check stakes and to use a bit of the fabric to sure up the downhill side of your beds.  On top of the fabric, I would put small wood which would create a barrier for the soil.  

well, we may end up using check logs but these are some long beds and in the end prolly gonna be at least 8 of them so it will take some time collecting all the material. The plan as of now is to just mulch the downhill edge of beds with hardwood and keep an eye out over time. Our walkways between beds are 2 feet wide and about a foot deep so we'll have little swales in between the rows so hopefully that'll help.

We have a number of beds in Western NC on some pretty steep slopes.  There are some questions you are going to need to answer to see how well they will do.

How tall are the beds?

Type of Soil?

What are you filling the bed with?

Where is the water coming from?

We went all modern and have heights ranging from ground level on the back to 3-5 feet high on the front terrace paths.  We broke the beds up in 4-6 foot lengths.  

We have had some issues with bowing in a longer length and higher height bed.  Too much soil/water pressure.  Even then it held up fine, but we plan to take that one down, add a central brace, and more drainage, because I am a neatnik and the bowing bothers me.

We are building beds in heavy clay and we do drive down posts ever so often.  No need for anything fancy with cement etc b/c it is solid clay.  I have seen it done with rebar as well to help tie into the soil in at least a few places. This has been for my peace of mind and has keep them pretty much exactly in place.  I have a cement curb to gauge the first tier on and I have seen less than a quarter inch of movement away from the road.

Another issue is the soil makeup that fills the beds.  We fill ours with old wood hugelkultur style.  This puts a lot less pressure than a full soil mix and allows good drainage.

Finally I have back beds on a major slope that receives a ton of runoff from ill placed concrete driveways (I'm working on this issue from the previous owners).  We built them the same way with boards and occasional posts BUT we left good sized gaps at the ends of baords to allow drainage holes.  These aren't as tall as the front beds just 1-3 feet but stretch for long continuous spans of 10-12 feet.  Zero issues with those and surprisingly not a ton of dirt comes out the gaps.  There was too much water to enclose them fully without some significant engineering.  This was a nice compromise.

Kermit, I'll also mention compromise.

When I designed our kitchen garden on the south facing slope behind our house, the angles were varied between almost flat and very sloped at around 22°. We made the raised beds (About 18 years ago) on contour and initially I wanted to make them all quite narrow so that I'd never have to walk on them but that was totally impractical for the amount of work it was to put in all the retaining poles.



I rethought the shapes and considered the types of plants that would need a much larger space - Jerusalem artichokes, artichokes, shrubs, irises, rhubarb, pumpkin etc. and designed the size of the beds around the big plants that wouldn't need tending to often.



In the end we had hugelkultur beds of different sizes, which were much larger that "recommended" but the shape and layout of the beds has evolved over time and I can garden easily without walking too much on good earth.



I also think it make the garden more interesting if you don't have rows of beds all the same size/shape - but that's just me.

Thanks for all y'alls input and replies. So yeah Wallace, we are not using any check materials to hold back the soil because the slope is not that steep and we will have a long non-hugel swale up top above the beds (about 60 feet long, 2 foot deep) with the berm bed about 5 feet max across in spots). We're making them long without breaks in the entire planting area because we're trying to keep it simple for irrigation, because we will still need drip irrigation given the summer temps here in the Piedmont (90's+ May to September), plus we are downtown Greensboro and it gets hot with all of the asphalt and urban heating effect in general.

I've seen these types of contour beds without any check materials (logs, wattle fencing, rocks) in other countries with even a higher rainfall average so I just said the hell with it and we're going for it because scavenging all the materials for a check system for these long beds, with a height of one foot on the downslope, would just take too long. However, we are mulching the downhill of berms/beds with hardwood mulch and planting russian comfrey every 4 feet over time to help hold the soil back and if we see that the comfrey ain't workin' then we'll have no choice but the install a check log system or something like that at a pace we can manage. We're renting the excavator on Tuesday of next week, then placing the fabric scraps and topsoil the next day on at least the first bed, and then installing irrigation and planting on the third day, and mulching the next.... if we have any go-go juice left that week.

This garden is a NAACP initiative and will be used to supplement the lean times that folks can experience during certain times of the year here in Greensboro. We're going with perennial plantings every other bed so the new garden will act as an extension of the already established orchard/food forest adjacent lending itself to year-ish round production.

You can see our trials and tribulations on Insta if you want @blackdiamondgso