Beaver Creek, not much more than a trickle, has cut a wide valley.
It's sort of like what we were told in Cub Scouts, and on PBS nature shows: water flows downhill, and as it goes it dislodges the earth, carries it away, and drops it when the current slows. It's a good working model, especially when one is trying to keep one's cornfield from washing away, or when explaining the Grand Canyon. It's a slip of a creek, with barely enough spring flow to allow minnows to survive in its deeper pools, just enough of a creek to justify a pause:
But Beaver Creek's bottom lands are much more complicated than its quiet music would suggest. Near the Meremec River, where the creek ends, the creek's bottoms are full of swales and depressions. It must turn into a puddled up bog when it rains.
These small dips and rises continue in the bottom land upstream, at least as far as I went. Some water must move through the low swales when it rains; however, there doesn't seem to be any stream cutting into them, and they don't really seem to be heading anywhere. I couldn't quite figure out what was going on. The whole process of erosion seems a very messy business at Beaver Creek, far messier that the creek's little dribble would justify.
I finally gave up on trying to puzzle it out, sat down and ate lunch. I found a nice gravel bar, and watched the minnows in the pool at my feet (Minnows in a tiny creek behave exactly like trout in a stream. They rest in feeding stations, out of the main force of the current, and feed opportunistically on whatever the current carries past. Just like trout.) I was sitting on a gravel bar, a recently formed one, largely free of vegetation. The creek was cutting into the opposite bank, then was forced into a ninety degree turn, and forced into another. At one point, its twists had pulled a tree down, exposing a section of bank, where it was cutting in earnest:
I suspect that most of the time, the creek isn't eroding its valley down to the Meremec. Instead, most of the time it's doing what I saw it doing at my lunch stop. It's cutting its banks and laying down gravel bars. It cuts its banks when it can. And when it can't, perhaps because trees have stabilized the bank, it turns. Sometimes if brings down a tree, which causes the creek to erode or deposit differently. And so, over time--over a long, long time--the creek wanders back and forth across its valley, changing its course, carving new paths according to a rhythm set by the lifespans of the trees along its banks.
Sometimes, as it cuts a new channel, it abandons an old one, leaving a depression into which accumulate material, and which eventually fill enough to form the swales and depressions I noticed when I first entered the valley. The swales are, we might say, the consequences of all the gravel pushed around by the creek, the remains of dance dictated by all the trees which ever lived in its valley.