Tuesday, June 22, 2010

Dam vs. soil erosion

Soil erosion is a natural phenomenon, like rain and drought, like day and night, like winter and summer. But if one wishes to minimize if not control such soil loss mainly due to heavy rains and flooding, one has to build dam checks and obstruction, man-made or natural, in order to trap a big portion of the eroded soil brought down by flash floods.

And this is one of the small dams we built in our farm made of stones, no cement.

It is about 4 feet high already starting from the base. The base used to be the “ground level”. We built it more than a year ago only, and during the last rainy season, it has trapped eroded soil and organic matter from higher elevation about 2 feet high.

Here’s another view of the stone dam. There is a small coconut tree that has grown near its base. This tree should help stabilize the base.

Here’s the back view of the dam, below. A layer of smaller stones stabilize the front layer of big stones. The force of the oncoming flood will hit the back layer first and the excess water will overflow on top.

This back layer is the one that will trap the eroded soil and organic matter brought down by the flood. Thus, after sometime, the back layer of stones will disappear and will be covered by new soil. Notice the leaves that we deposited at the back as initial deposit of organic matter.

And here’s the top view, below. There are now 3 layers or stone terraces in this dam. The 2nd and 3rd layers from the right are actually sitting on the trapped soil by the 1st layer (rightmost) of stones that we built last year.

The width of this 3rd and last layer of stones is about 1 ½ foot. When new soil has reached the level of this last layer, then a 4th and new layer of stones will be built on this new soil. And so on until this dam gets higher and higher, trapping several cubic meters of eroded soil from higher elevation every year.

This is the gully that we hope will be slowly covered by new soil every year.

What’s the point of doing these things? Well, three points. One, minimize and control soil erosion. Two, improve the water retention capacity of this part of the farm, creating a new water table someday. And third, build bigger and higher stone terraces, without cement, and have a beautiful layers of big stones rising up every year. Should be a beautiful spot for picture taking someday. :-)

Above are the guys who helped me build the 3rd layer of stones just last weekend. Our caretaker in the farm is Nong Endring Paragas, right most. He is also one of my wedding godfathers. Assisting him is his son, Danny Paragas, leftmost, who also got me as one of his wedding godfathers, and the world is turning round and round. :-) In the middle are two teen-agers who work for 1 day with us, Hardji and Marlon, and both are nephews of Danny.

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