Rebuilding the Dam

A couple years ago, we tried to build a small earthen dam to stop debris from the woods from being washed out into the pastures during spring rains / snow melt. That attempt didn’t hold.

Here is the completed earthen dam a couple of years ago before it was tested.

Instead of rebuilding the earthen dam to completely block the water by holding it back, I decided to fortify the remaining piece of earthen dam with a water-permeable dam instead. By creating a water-permeable dam, the water would still flow through the dam out into the pastures, but the leaves, rocks and tree limbs would remain in the woods leaving the fences and pastures undamaged after the water subsides and avoiding the need for any time spent on clean up. The dam should slow the flowing water, causing the debris to stop while the water would continue seeping slowly through the dam out into the fields.

The same view of the dam today (including the water-permeable portion where it was previously washed out). It has been so successful that plants have been able to establish themselves over the dam as they are not washed away during heavy rains.

But what could we use to make the water-permeable dam? It would need to allow water through yet be sturdy enough to generally hold its shape under pressure from the flowing water without itself washing away.

Luckily, we had just the items we needed already on hand. Grain sacks (in which our goat grain is packed) are woven together so are naturally water-permeable but are too flimsy on their own to serve as a dam. As the dam is near the small creek that overflows, we also had the second item we needed nearby – lots of rocks! Rocks are heavy but a pile of rocks is still water-permeable. A pile of rocks on its own might not work as the individual rocks can be shifted and washed away. But rocks combined with the grain sacks is a food solution.

The price was definitely right as everything was free besides the manual labor to assemble it.

Grain sacks filled with rocks.

We filled at least a half dozen or so empty grain sacks with loads of rock from the creek bed. We put the now rock-filled grain sacks into the breach in the dam. The rocks provide sufficient weight for the dam while the grain sacks stop the rocks from being washed away. Result is a pretty quick and easy water-permeable dam.

The water-permeable portion of the dam. You can see the pile of leaves and debris stopped from being washed into the pastures.

The new water-permeable dam has been a great success. Debris is no longer washing out into the pastures which means no damage and no pasture clean up time. There may come a time where either the dam height needs to be increased or some debris cleared away from behind the dam or else the debris may pile up high enough to go over the top of the dam.

A view from upstream in the woods. You can see the white grain sacks in the background and the piles of leaves and debris forming on this side (i.e., behind) the dam.

We now know the secret to building a good water-permeable dam so it would be a quick fix to increase the height – we always have the free materials on hand.

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