Sunday, February 25, 2018

No Swales

I've often been asked by people not familiar with my area of Hawaii, if I have built swales on my farm. Truthfully, no need. The ground here on the farm drains because it is fractured lava. Rain runoff is not an issue. Even if I wanted to capture rain runoff around the farm using swales, I couldn't on 99% of the place. 

There are generally only two situations where I don't see natural drainage.....#1- down on the flat pahoehoe lava where a previous owner added several truckloads of cinder and compacted it in anticipation of building a barn. Good thing he didn't because the area now floods. His modification blocked the natural drainage system.  I had to create draining trenches to remedy the water problem. #2- the driveway. Since the driveway is compacted, it's understandable that the rain runs off. 

Photo....rain accumulating in the tire tracks. 

Driveway.......rather than building rain bars to divert the water off the driveway, I am taking advantage of the runoff by letting it run down the tire tracks then diverting it to the two hugelpits that run on either side of the driveway. The tire tracks don't become bogged down in mud because the driveway, as with the ground here, is lava rock with a little dirt between the rocks. We have put a thin layer of coarse gravel atop the driveway, and over time the vehicles grind it into coarse sand. That sand will wash out during torrential rains, once again exposing the lava driveway. No big deal. It just means that new gravel needs to be shoveled into the tire tracks again. The gravel is there just to make our ride up the driveway smoother, more pleasant, easier on the low slung cars. 

Photo....water runoff coming down the driveway. 

The hugelpits are gigantic sponges and thus far have taken all the water Mother Nature has produced. I think this is a good way to bank that water and have it available for the bananas and turmeric that grow on the hugelpits. 

Photo....bananas growing in one of the hugelpits along the driveway. 

Just a note.......this past summer I mined sections of the top 2 to 3 foot of material out of one of the hugelpits. I needed "compost-soil" for another project. It had been two years since much of the pit had been topped off. The mulchy soil looked great and was moist - no surprise. But what did surprise me was that 3 foot down into the hugelpit the fill was on the dry-ish side. The top 3 foot had sponged up the water and not so much was getting into the lower layers. That means that most of the rain runoff was being captured and there wasn't excess, thus flooding the pit. So this gigantic hugelpit was capable of capturing a lot, lot more runoff. It's holding capacity is enormous. The pit is actually over 6 foot deep in most places. So it should be able to capture quite a bit of water.  

Photo.....water runoff running through the shallow drainage channel and into the hugelpit. It was pouring rain when I took the photo, so there's lots of water.

Based upon this information, I terminated the rain runoff channels higher up the driveway and directed most of the runoff to the pits, now knowing that they can handle it. For some reason I feel smug knowing that I'm not wasting the rain runoff. Instead I'm banking it for my crops. 

Diverting the water to the exact location in the hugelpit is simple. I use a hoe to scrap an inch deep channel. Then the water flows exactly where I want. With such a simple set up, I can block off a channel or create a new one at will. This way I can get water to flow into the hugelpit at any spot I think could use it. 

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