Snarled Drift at Snarl Street

The 99wetlands project is less deliberate and planned than you might imagine. In fact, sometimes a wetland’s name is enough to pique my interest, and I allow serendipity to carry me along. I saw “Snarl Street Wetlands” in the atlas, and I just had to visit the site! And so I found myself on a sunny autumn day, resting along the banks of the Iowa River  eating my lunch. As I ate my sandwich, I looked up and noticed something “snarled” in the branch overhanging the river channel: a bit of tangled debris. And then I noticed a bit more, and a bit more, all at a similar height above my head, suspended over the river channel. I was looking at snarled drift: it had been floating on the surface of the water during a flood, and was caught in the branches, where it remains. DSC_0569

This is a so-called “field indicator of hydrology,” some physical evidence of the river stage (height of the water surface) during a past flood. The straightened river channel before me was obvious physical evidence of a human response to flooding: an attempt to cause the river to flow more efficiently, draining the land more quickly. Other evidence around me suggested that the goal was to farm the land. For example, I noted old fence and wire nearby — it had likely enclosed pasture land.

DSC_0571

Now that we have the observations, let’s hear the backstory. I corresponded with Jake from the Wright County Conservation Board, who told me a bit more about this nearly-120 acre (50 hectare) parcel located just west of Rowan. I was informed that sure enough, the parcel had been farmed but “is prone to seasonal flooding so it was put into a wetland easement prior to purchase” by the county in 1998. Looking at old aerial photos, I can tell the site was nearly treeless and the river straightened already by the 1930s; over the succeeding five decades, trees grew up along the river channel itself while the adjacent land was worked. In various photos it appeared to often be pasture or hayfield, and I imagine the farmer would have realized that the low fields flooded too often (frequency) for too long a time (duration) to allow row crops, so a strategy of adaptation to flooding would make sense. And indeed, hydrologists do consider both frequency and duration in considering flood effect. As I observe the tangled drift caught in the branches above me, I also think of the height of the water too, and of the massive amount of materials that water carries during a flood. No doubt, flooding is a dominant force in this ecosystem, and organisms must respond to it appropriately.

I have often admired how Silver Maples (Acer saccahrinum) like these can grow along such a floody river. The Iowa Flood Information System maps suggest this site floods, on average, every second year (i.e., 50% flood risk any given year). What stresses do the trees face? What special adaptations do they have? Adaptations allowing the plants to anchor securely in place are necessary when facing moving water near the stream channel. Adaptations allowing cells and tissues to withstand submersion (and therefore lack of access to air) will be important physiological traits. These might be interesting topics for future blog posts!

“But Paul,” you say.  “Why is it called the SNARL STREET wetlands?” Well, I’m told that the adjacent road had quite a reputation with the locals for rough going, especially in winter. I found the drive easy, but no doubt in years past it would have been a slog. At least some of that might be related to the river flooding. Seems traffic had a bit of a snarl on the road near the swamp!

Thanks for reading. I hope to “snarl” your attention with future posts! Watch for another entry every “Wetlands Wednesday.”

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Author: Paul Weihe

Associate Professor of Biology at Central College, traditional author (Textbook of Limnology, Cole & Weihe, 5th ed.; Waveland Press), and now...blogger!

One thought on “Snarled Drift at Snarl Street”

  1. The part about silver maples makes me wonder — what do we know about what used to grow along creeks and small rivers before European settlement? Iowa’s landscape and hydrology have been changed so profoundly since then that it’s hard to imagine a time when large fires swept freely across the landscape and wet/water areas were not straightened or drained. Were there fewer riparian trees and shrubs and more prairie and sedge meadow ecosystems growing right up to the edges of waterways?

    I’ve seen how a little formerly-pastured treeless wet riparian area, once livestock were removed, was completely taken over by large woodies in just thirty years, a short time by landscape-history standards. Was that a microcosm of what happened in many Iowa places?

    On another topic, I’m now listening to a radio show on which an author is saying that early Upper Midwest settlers and farmers are often assumed to have hated wetlands, so that they did everything they could to drain local wetlands as fast as possible. But she says that sometimes the reality was that the local settlers and small farmers liked the wetlands and used the goods and services wetlands had to offer. It was sometimes wealthy out-of-town land speculators who were determined to drain the wetlands in order to make money, and the speculators had the funding, political clout, and large equipment to get the drainage done even if locals objected. Interesting!

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