What are these pits for?

[MickyB]

Does anyone know what these pits are for? I often see them along dirt roads and tracks and always on the 'high' side of the road. They are generally every 20m-50m apart. I originally thought it might have had something to do with drainage however often there doesn't appear to be any gutters directing the water towards them and the road slopes away from them.

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[Moondog55]

Do you find an associated culvert on the downhill side of the road?

[MickyB]

Do you find an associated culvert on the downhill side of the road?

I have never actually got out of the car to look but there never appears to be any evidence of one being there. I have see freshly dug pits and the road always seem in 'original' condition so I don't think they have dug it up to put a culvert in. Also some of the pits have been full of water days after the last lot of rain.

[Moondog55]

Quick small gold mines?

[MickyB]

Quick small gold mines?

Haha. Yeah, maybe

I'll be going up one of these tracks on Friday so I'll have a better look then.

[Count]

There could be a pipe toward the top of the pit taking water under the road to the other side and then 'downhill'. As a means of reducing erosion on the high side?
I don't actually know...
I was wondering the same thing about some pits toward the top of Mt Kosciusko, which didn't look like they belonged, and I couldn't tell what they were for?

[TeaTreeTea]

Those pits at Kosi have me puzzled too...

[MickyB]

I drove along a track yesterday morning and saw some more of these pits. I stopped and had a good look at them and they were just a hole at the side on the track with no pipes to divert water away and limited guttering directing water to these pits. However in the arvo I drove along another track and saw some pits that were slightly different. These pits had two holes side by side with guttering directing water towards them. The second pit had a pipe running under the road from it to the downhill side of the road. Although there was no water in them it looked like the first pit acted like a filter, collecting leaves, bark and branches. Once that pit was full of water it would overflow into the second with excess water in that pit escaping through the pipe underground. Maybe the first lot of pits that I saw were just badly placed or needed maintenance to improve the guttering.

[keithy]

Hmmmm.. I saw the same pits walking though logging forest tracks in New Zealand as well. I meant to ask what they were for.

Some in NZ were half filled with water, while others dry.

[ribuck]

Could they be drainage test pits? These are dug before work is done on a road, to see how quickly it drains and therefore what kind of additional drainage must be provided. A Google Images search for "drainage test pits" brings up images that look very much like this.

[CasualNerd]

I think they're just silt collection points along drains where there's a lot of erosion or vegetation falling. Mud and silt collects in the bottom, then only clearer water overflows that into the actual drain and doesn't block pipes going under the road. You sometimes see them behind a haybale or shadecloth screen that further filters the runoff.

[Strider]

I think they're just silt collection points along drains where there's a lot of erosion or vegetation falling. Mud and silt collects in the bottom, then only clearer water overflows that into the actual drain and doesn't block pipes going under the road. You sometimes see them behind a haybale or shadecloth screen that further filters the runoff.

I reckon you're onto something here.

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[MickyB]

Could they be drainage test pits? These are dug before work is done on a road, to see how quickly it drains and therefore what kind of additional drainage must be provided. A Google Images search for "drainage test pits" brings up images that look very much like this.

Maybe but I doubt it. The roads have been there a lot longer than the pits.

I think they're just silt collection points along drains where there's a lot of erosion or vegetation falling. Mud and silt collects in the bottom, then only clearer water overflows that into the actual drain and doesn't block pipes going under the road. You sometimes see them behind a haybale or shadecloth screen that further filters the runoff.

I agree with you for the pits I saw yesterday afternoon but what about for the pits with no guttering for water going into them or pipes for water to exit? I must admit I didn't stop at everyone that I saw so maybe there is a pipe every second or third pit. That doesn't explain the lack of gutters but as I mentioned earlier maybe that is just lack of maintenance.