How Steep is Too Steep?

Hello everyone,

Just wanted an opinion on a piece o' land. It's located in Eastern Portugal in a natural park with lots of large fauna. It's 24 acres - which is big enough, by my standards. It's got a house with a roof on it, ready to be done up; groves of olive, vines, and other fruit and nut trees in the bottom of a fertile valley, a section of river with a ruined water mill, which could one day  be restored to functionality, aaaaaaand... a big old chunk of a mountain.

I love most aspects of this property and the price is good. Seems like it could be what we're looking for, but I'm uncertain about... the hill.

The agent says no one has bought it because of the slope. No good for animals or agriculture, he says. I know that's not neccessarily true. It faces South East, so it should get the sun. I don't mind climbing it - I'm more concerned about it being, I don't know... somehow unusable?  The bedrock in this area is granite and it seems like terracing it would be incredibly labour intensive - maybe not even a good idea in terms of soil disturbance.

There are already established trees on the slope, which means it must have enough stable top soil to support them - although part of it (the bald part on the satellite map) seems too steep for trees. It may have been cleared though.

What could be done with a mountainside like this? Is it entirely non-ideal? Is it going to make everything 1000x more difficult than it needs to be, or does it actually have some advantages? Any of you guys worked with something like this? What would you do with it?

We'd like to have a couple of mules and some kind of flock - probably goats in this area since they like hills. I'd likely put most of the 'garden' in the bottom of the valley near the house (just the flat bit is a mile in total area). I'd ideally grow things on the mountain as well though - maybe an orchard?

I guess I'm just not confident in my notion that this seems like a good deal? It's certainly hard to find land this size, for this price, with a house already on it. Would the mountain be a deal-breaker for you?

Are you aware of the plant vetiver? It is a bunching grass that can be planted to form dense hedges on contour. The hedges slow down surface water run off and trap sediments on the upslope side of them. They are excellent at stabilising steep slopes and building soil. Over time they help to build natural terraces between the rows, and the gaps between rows can be used for planting.

The vetiver can be cut once or twice each year, using a hedge cutter, and the long grass makes a great mulch to help build soil and store water.

The climate in portugal should be excellent for it. It will like the warm climate, and can cope with the winter temperatures you are likely to experience.

Here you can see the difference in soil height either side of a vetiver hedge. The soil has been moved and trapped by natural processes, not by manual terracing


Here is a cross section through an established hedge. You can clearly see the original soil line, and the new soil build up. This is soil build up after just two years from planting.


Vetiver propagates easily - an established clump can be divided after 12 months to make hundreds of new slips for planting, and it is sterile so will not produce seed and spread.

Given your description of the land I think vetiver would be an ideal solution to transform portions of it. The steepness sounds unsuited to traditional terracing or swales, but you might get much the same benefits with vetiver.

I have just seen in your other post that fire is a concern. Here is how vetiver responds to fire:

Michael, this is amazing and just the kind of niche knowledge I was looking for! Thank you.

I've never heard of vetiver, but from your description (and the convincing images) it sounds like it could be a great solution. I will do some further research and discuss it with my partner. Very promising and its fire resistance is an added bonus!

Hi Rudyard! This sounds cool! Our place is also quite slope-y (roughly 250 m rise over 1200 m in total, and some parts very steep) and facing southish. We're in a very different climate from you (Norwegian coast) but even so. I wish we had started a few years earlier, to have a bit more high-quality input, but as it is we only bought our place last year and haven't had time to do so much yet. If you do end up buying it, it would be nice to share experience as we go...

A couple of unqualified thoughts:
-Orchards/forest garden sounds like a good idea for the steep parts. As you said, massive soil disturbance in steep terrain might not be so good, so I think it's a good idea to confine any growing of annuals to the flat parts of the property. This would minimize the risk that all that lovely garden soil, unbound by tree roots, er, moves downhill. Vetiver hedges would probably mitigate this, but since you have a flat area anyways, and next to the house no less...
-Another good thing about using the steep area for the growing of trees, especially considering that it has a south aspect, is that you can grow sun-loving species without clearing away so much of the existing tree cover. I suppose this will be a smaller problem for you, since you are way further south, but when we considered whether to buy our place we tried to calculate how big a patch of forest we'd have to cut to get full sun anywhere. The result was not encouraging, but as it turns out , there are a few spots that already have pretty much full sun due to the slope in conjunction with existing clearings and gaps in the canopy.
-Probably obvious one, but bear in mind that goats might be tricky to combine with gardens, and that very steep parts might be hard to fence adequately.

I think the place sounds lovely. If it was me, I'd buy it.

I've got fairly substantially sloped land here (about 6 1/2 acres), but in a very different climate again. The house is at the top rather than the bottom of the slope. I tend to garden on the flatter bits - the main area is planted with trees which I coppcie for woodfuel. We have a grassed access track which we can use to take a vehicle round if neccessary, but I generally just walk and use a wheelbarrow for pottering about!
Having a slope will make using vehcles more difficult if you are intending to use the area for harvesting anything, as well as the risks of erosion etc. The soil type and depth and vegetation cover also makes a difference to the erosion risk. I would suggest finding out the slope - how steep it is, what sort of soil covers the granite, and investigating that bare area. Trees can grow here on any area the sheep can't reach, but you may be more water limited.

I found a few post here that may help.

https://permies.com/t/120024/Potential-homestead-slope-Kitchen-garden

https://permies.com/t/135291/transform-heavy-clay-steep-slope

https://permies.com/t/135041/working-slopes-gradient

https://permies.com/t/149598/earthworks-property

https://permies.com/t/147029/Equipment-steep-slope-cut-swale

https://permies.com/t/145816/Square-foot-garden-Wow-Dipper

if you subtract the value of the "usable" land and the house, including things like driveway, well and septic, from the asking price; what is left. Or; how much are you paying for the steep portion of the property.

Don't forget you're losing the ability do do a lot more than not being able to plant this or that. You won't be able to build a plan of houses, and lots of other things. If you plant an orchard will you be able to run a tractor on the slopes. How much is that remaining land really worth. If you own useless land they will still tax it.

Without contours, it is difficult to tell how steep the hill is.  I have seen cattle grazing on incredibly steep slopes in the SW Virginia and NW North Carolina, USA.

Very cool plant there, vetiver. Thanks Michael!

Also, I second that you should show contour lines so we can see how steep it is. The property is intriguing for sure!

That sounds a lot like my property, in a similar part of the world with SE slope, a house already here, a west coast nearby, at 1500-1800 ft, Lat 41.7N.  I have been here about two years and love it so far but of course working with an average 10deg slope has pros and cons. Pros are potential kinetic energy, light exposure, drainage (flooding is for suckers), views, microclimate variability, naturally exercising more, a sled run for my niece. Cons are of course erosion and other shit falling down hill, fire running uphill 6x the speed as on flatland, and snow is a greater hazard. Overall I love it, but I am a mountain person at heart.

One real consideration is how 15deg is considered the maximum reliable and sustainable slope for trailbuilding (one of my jobs). This is similar for roads. Roads and trails of course both have examples of steeper slopes, but when building or rerouting a trail one major consideration is that anything over 15deg is not going to be worth the increased maintenance and likely/eventually will collapse/washout catastrophically in places.

Not a deal-breaker, as long as there is also some flatter land and the house is safely far away from the mountain. Check the landslide risk if you can.

My land has a steep slope at one end also, so I can say that a 1:3 slope (1 unit rise per 3 units run) of silty clay loam is too steep to cultivate. I know this because it has had landslides from that slope in the past, and I don't want to increase the risk.

With a slope that steep, the goal is to not disturb the trees whose roots are stabilizing the slope, and to minimize water retention. It's not suited to farming, because removing the trees would destabilize the slope and terracing would increase water retention. It might be possible to run livestock, but I would avoid anything likely to dig around and tear up the soil or denude the stabilizing vegetation. Personally, I choose to leave it to the wildlife.

The rest of my land averages around a 1:8 slope and hummocky, which gives me a mix of workably even areas and some overly steep bits between.

I hope these examples help give you an idea of where your land falls on the scale.

[Edited to fix my math on the slope calculations. I can't read a contour map, it seems.]

If you decide to plant fruit/nut trees on the steep part, I recommend adding some kind of anchoring points for ladders and/or scaffolding. Because at some point, you're going to want to pick from the branches that are hardest to reach, and an un-anchored ladder on a steep slope is just asking for trouble!

For those following the thread: I did my slope calcs wrong because I can't read a contour map. I will be editing my post accordingly, but the quick and dirty is that the "too steep" slope was 1:3 and the workable slope was about 1:8.

Eino Kenttä wrote:
-Orchards/forest garden sounds like a good idea for the steep parts. As you said, massive soil disturbance in steep terrain might not be so good, so I think it's a good idea to confine any growing of annuals to the flat parts of the property. This would minimize the risk that all that lovely garden soil, unbound by tree roots, er, moves downhill. Vetiver hedges would probably mitigate this, but since you have a flat area anyways, and next to the house no less...
-Another good thing about using the steep area for the growing of trees, especially considering that it has a south aspect, is that you can grow sun-loving species without clearing away so much of the existing tree cover...
-Probably obvious one, but bear in mind that goats might be tricky to combine with gardens, and that very steep parts might be hard to fence adequately.

Hi Eino,

I'd love to share experiences with you. Your point about the slope allowing sun loving trees without clearing is a good one - and not something I had considered. I think orchard or food forest would definitely be the way to go.

Yes - I've heard goats can be difficult to contain. My experience with them is limited. I know a little bit more about cattle. I'd have to give it some thought and maybe come up with a system of seasonal corrals, combined with possibly shepherd-style grazing in the mountains.

Nancy, thank you for the links, I will give those all a read!

John Indaburgh wrote:
if you subtract the value of the "usable" land and the house, including things like driveway, well and septic, from the asking price; what is left

This is a good point too. The flat part is about a square mile and the slope is 1.5 miles square, so it is the larger part of the property. I suppose it's a matter of whether we can get enough use out of it to justify its existence. The price is less than a euro per square metre, so it's very reasonable for what it is and I don't believe it would be totally useless. It might have added challenges, yes, but on the other hand if it were totally flat, the land would be well out of my price range! I wouldn't be seeking planning permission for any more houses or anything like that and I'd probably favour a mule over a tractor. But yeah, it needs to be weighed up.

Dan Fish wrote:
Also, I second that you should show contour lines so we can see how steep it is. The property is intriguing for sure!

I will try and find a survey map with contour lines. At the moment the only visualisation I have seen is GoogleEarth's 3d rendering of the elevation. I've attached a couple more pictures showing the hillside with mature trees.

Ellendra Nauriel wrote:anchoring points for ladders and/or scaffolding

Yes, it would require some thoughtful planning. I don't fancy falling off the side of the mountain!

Thanks for those pictures, they really help get a sense of what the land is like.

Question - do you NEED to do anything with the mountain side? I there are pressing reason to make changes at all? My feeling is that the flat land is plenty to keep you busy.

Sepp Holzer farms very steep mountainous land. His climate is very different from yours, but I am sure there are parallels. He makes extensive use of earth moving to build terraces and fertile spaces and microclimates. Well worth a read.

One lesson you can take from him is the use of livestock to harvest the product for you. For example, he plants fruit trees on slopes. Fruit falls and rolls down to terraces. His livestock eat the fallen fruit. His end product is the livestock. I think he makes use of electric fencing to keep animals in the appropriate areas. You might consider what this might look life for your own climate.

Wild boar is pretty common in your area I think. You could plant crop trees that attract wild boar when the fruit falls and cull the boar when they are foraging on the fruit.

My other thoughts are centred around water harvesting. It looks like you have some natural gullies cutting through the plot. Have you seen what they are like after rainfall? Is there evidence of erosion and channelling? Would water retention measures upslope benefit your flat land projects down slope? I'm thinking a combination of check dams, vetiver hedges, and wild life ponds. The more of the rainfall you can trap upslope in streams, and in the ground water, the more resilient your landscape will be in droughts and hot weather.

Judging from the pictures, I would go for it.  Of course, I would use the statements made by the realtor (?) to get the lowest price I could.

Rudyard Blake wrote:

Ellendra Nauriel wrote:anchoring points for ladders and/or scaffolding

Yes, it would require some thoughtful planning. I don't fancy falling off the side of the mountain!

a good tripod orchard ladder could partially solve that problem if they’re available in your part of the world (depending on the eventual height of the trees you’ll be picking from).

That's a very interesting property. I like it! But then I like all mountains.

I'll echo the comments made previously. I would buy it IF ...

- you can do essentially everything you need on the flat portion

- you are not being taxed at the same rate as desirable flat land

- there are no unusual restrictions on building on top of the mountain (e.g., a wireless internet tower, though ugly, would generate passive income for you and make your neighbours happy .. same goes for a windmill)

- the mountain needs little or no maintenance (not covered in invasive weeds that you are required to control)

greg mosser wrote:

Rudyard Blake wrote:

Ellendra Nauriel wrote:anchoring points for ladders and/or scaffolding

Yes, it would require some thoughtful planning. I don't fancy falling off the side of the mountain!

a good tripod orchard ladder could partially solve that problem if they’re available in your part of the world (depending on the eventual height of the trees you’ll be picking from).

My partner used to build treehouses for a living, so maybe we could rig up some kind of platform/ladder combination.

Michael Cox wrote:
Question - do you NEED to do anything with the mountain side...

I don't need to do anything, but ideally it should contribute something, even if it's just a place for nature. I like the idea of gardening in the flat, and leaving the hill as a more natural orchard (with vetiver terraces!) offering foraging for livestock and wildlife. The local farmers would probably argue that that would not constitute 'doing' much with it, but they have a very different perspective on the utility of land.

Yes - there are many boar! As well as red, roe and fallow deer. I'd very much like to get a hunting licence in Portugal and if the boar could be encouraged to visit our property to get fat, we could eat very well. I will look up what Sepp Holzer has done with his mountain. I also like idea of fruit rolling down to the terraces - I think that would be do-able.

And your ideas about water catchment are good. I had considered making a small diversion of the river at the bottom, and trying to get it to flow through a series of ponds with willow borders, maybe with fish in them. Something like that. I am not an expert in aquaculture though. Nor have I seen the property in all seasons. My partner is going there in a few days to take some more photos.

John F Dean wrote:
Judging from the pictures, I would go for it.  Of course, I would use the statements made by the realtor (?) to get the lowest price I could.

That's the plan! He said if it were flat, someone would have bought it by now, so we're hoping no-one else is interested. Hopefully we can knock him down even more.

Michael Cox wrote:Thanks for those pictures, they really help get a sense of what the land is like.

Question - do you NEED to do anything with the mountain side? I there are pressing reason to make changes at all? My feeling is that the flat land is plenty to keep you busy.

I completely agree with this.  Unless you intend to do some sort of commercial growing, I think your flat (which already has fruit trees??) will be plenty.  

Further, now that I've scrolled and seen the photos of the hillside, that doesn't look like much of a hill to me at all.  (a lot of my [unusable] land is steeper than a staircase.  That hill looks like a pleasant slope, easy for animals to wander around.  

and I also agree with the wild pig worries.  Build everything pig proof.

Looks like a great opportunity.

I have seen cattle grazing on slopes more impressive than that.  No, it is not quality farm land, but it is good enough and can be put to good use in a variety of ways.

Tys Sniffen wrote:

Michael Cox wrote:Thanks for those pictures, they really help get a sense of what the land is like.

Question - do you NEED to do anything with the mountain side? I there are pressing reason to make changes at all? My feeling is that the flat land is plenty to keep you busy.

I completely agree with this.  Unless you intend to do some sort of commercial growing, I think your flat (which already has fruit trees??) will be plenty.  

Further, now that I've scrolled and seen the photos of the hillside, that doesn't look like much of a hill to me at all.  (a lot of my [unusable] land is steeper than a staircase.  That hill looks like a pleasant slope, easy for animals to wander around.  

and I also agree with the wild pig worries.  Build everything pig proof.

Looks like a great opportunity.

I've managed to find a way to show the elevation profile in Google Earth. It's not as steep as I thought either. I'm feeling a lot more positive about it.

And yes, the flat already has some fruits, nuts and olives. I'm probably massively underestimating how long that flat part would keep us busy!

Douglas Alpenstock wrote:That's a very interesting property. I like it! But then I like all mountains.

I'll echo the comments made previously. I would buy it IF ...

- you can do essentially everything you need on the flat portion

- you are not being taxed at the same rate as desirable flat land

- there are no unusual restrictions on building on top of the mountain (e.g., a wireless internet tower, though ugly, would generate passive income for you and make your neighbours happy .. same goes for a windmill)

- the mountain needs little or no maintenance (not covered in invasive weeds that you are required to control)

I will check the restrictions on it. The mountain is mainly native pine and scrub. I don't think there are any requirements beyond fire clearance requirements, but I feel that could be taken care of with herbivores.

Thank you everyone for your advice and great ideas!

90% of my land is 20% slope which is 18 degrees I think? I wouldn't want any steeper for my plans of meandering pathways...

It seems most property lines aren't really done in a way that allows the best on-contour traversing of an area...maybe for the entry off the nearest main road, and a building spot, but that's it. Fence lines especially make things challenging if the land was segmented for grazers. So it creates challenges.

For me, it's part of the fun trying to work with what you got. It's really hard to end up on a piece of land that is just perfect from every angle, you could end up searching your entire life and never find it. So eventually we settle. I've been cutting in roads and it's a lot of work, and yes there are spots where I can tell the erosion is going to be an issue. Learning to sculpt land above and below a road or planting bed, or even alongside can help these conditions but it does take time and even machinery depending on the scale.

Whats it worth to you? I happen to really like carving in roads and paths along the hills and they don't have to be perfect...some will be accessible by car during dry times, but others just for the 4x4 tractor and atv. For me the access across the property by machine is the foundation of everything from crop gardens to maintenance and observation of re-wilding areas. (The land was previously  used to make hay with tractors)

Being able to easily traverse your less-used areas to keep an eye out for vines or brush that may be damaging to some forest or wildflower re-growth is helpful.

It's good on my conscience to know I can always go do a pathway walk and have a great day getting exercise out in the hills scoping things out.

Did you ever figure your actual slope angles or percentages? I think anything is do-able with reasonable expectations and work.

Be very cautious about goats. They browse (eat bushes and trees Not Grass). They climb and denude trees. They are voracious escape artists who will chow down on everything that you need to keep on that slope