Ricochet is the best place on the internet to discuss the issues of the day, either through commenting on posts or writing your own for our active and dynamic community in a fully moderated environment. In addition, the Ricochet Audio Network offers over 50 original podcasts with new episodes released every day.
The stream was dammed for the old mill well before 1976. That’s the only certain date I can give, but by that time the old mill was gone and you had to be a digger to find its foundations (I was.) There were a couple of mature hickories growing in the ruins. Let’s say the dam had stood for a century, give or take a human generation.
It was a small earthen dam on a lowland stream, holding back a hundred acres of pond water that drained from a few thousand acres of forests and fields. It rose perhaps 15 feet from its base to the outlet, perhaps a bit less. It was simply but well constructed with a hard clay interior and plenty of earth above high water, for weight. Twin four-foot pipes at one end drained away beneath the adjacent road.
The road came after the dam, I think. It ran on a fill laid across the steep stream bottom, below the dam and intersecting at one end. The little pocket between the dam and the fill had its own culvert, which it needed because the dam seeped a little. I never saw water on the face, but the ground adjacent was muddy even in dry weather. That would have been the pond’s water column pressing on groundwater, that percolated up on the other side.
Most of the time the little system of pond, dam, and spillway was quiescent. When it rained the pond rose and the outlet pipes ran. When it was dry the water stayed below the outlet and stagnated. When the local beaver clan got too ambitious some responsible person would usually tear out their work. If they repeated the offense, well honestly, trapping those guys is a lot of bother. Back when it was my job, I let Mr. Savage handle it after dark.
Let’s stop and talk physics. Percolation is how we model the way fluid seeps through a porous barrier and similar physical situations. The math is nice and abstract; it’s based on the idea of a network of particles each in contact with its neighbors. Whether any gap lets fluid through is up to the nature of the fluid and the particles, and a bit of chance. Percolation of water through earth is driven by pressure — it takes force to push water through those gaps.
Let’s stop and talk engineering. An earthen dam can allow water to percolate within limits and still go on standing forever. As long as the percolating flow doesn’t go too fast with too much volume, the particles of earth won’t budge. Raise the pressure and more water will percolate, maybe starting to move a grain here and there.
When enough grains have moved to open a connected channel, the system has entered a new realm where percolation no longer matters. The phenomenon of interest now is erosion. As long as the water flows the channel will widen.
Let’s go back and talk physics. Pressure is a force, as is weight. The pressure at the base of a dam is the weight of the water above it. Deeper water, more pressure, more percolation. Now isn’t that so simple a caveman could get it?
Cue the ominous music. Some fool, it’s always some fool, decided to raise the water to improve the fishing. The damn pond already had great fishing, panfish, and predators — crappie, a range of bream, largemouth, and pike. Maybe the would-be Fish Lord wanted his picture in Field & Idiot or something.
A few dozen tons of riprap and rubble will stop a spillway in no time at all. Did you know that? He raised the outlet by three feet.
Nature didn’t get around to filling the additional impoundment for over a year, I’m told. I imagine the stagnant water became offensive in the summer. But Atlantic hurricanes can drop a lot of water a hundred miles inland. I forget which storm it was, might have started with ‘A.’ The dam had seen bigger storms every third year since it was built, but the extra depth and pressure this time were the end of it.
Witnesses told me that when the dam went, it went fast. The wall of water topped the road and ran long enough to take that too. The state repaired the road. The dam was private. The fool with the rocks moved away.
Most of the dam is intact today, only the middle quarter failed — the deepest part, of course. It was undercut by pressure driven seepage that evolved into erosion from beneath. The undisturbed core is plain to see in the remaining segments; it really was a fine dam. You can look at it today, the outlet pipes, the rockpile, the missing segment, and the swamp behind it all. The simple physical truth stares you in the face and says something completely unprintable.
There’s probably a metaphor here for a constitutional republic, one that delivered well on its original promises and good intent and could have gone on indefinitely. Then a few comfortable and privileged fools wanted more. Being privileged, they took that which properly belonged to the community into their own hands and remade it. Being fools, they broke it.
I’ll skip it, that’s too easy. Besides, our fools are still fishing in high water. As more and more outlets are blocked, however, I wonder what it will look like when the regime changes and the real erosion kicks in.