Cedar River Watershed Project: Messages from the River
Written by Larry Stone
Were the floods of 2008 trying to tell us something besides, “Gosh! What a lot of rain!”?
What about the apparent trend to higher and higher flood crests? Could this be more than just an unusually big rain or a freak wet spell?
Gary Siegwarth, manager of the Iowa Department of Natural Resources Big Spring Trout Hatchery along the Turkey River above Elkader, thinks we should pay attention to what our rivers are trying to tell us about their declining health.
For example, high mud banks line parts of the Cedar and other rivers. But many of those banks may not be natural. Old photos and records suggest they were formed a century or more ago as farmers first cleared native prairies and forests to plant crops, allowing virgin soils to erode into the valley.
While the complex of vegetation of the original landscape acted as a giant “sponge” that could absorb up to 8 inches of rain per hour, intensively farmed fields can soak up only fraction of the precipitation. When rainwater falls on a crop field, much of it sluices off, carrying topsoil with it, filling stream channels and floodplains with silt and sand. That problem has increased with the pressure to grow even more row crops. And the runoff from paved roads, parking lots, buildings, and urban lawns overloads the floodplain even more.
Thus, many rivers have lost touch with their historic stream channels, Siegwarth said. Rivers now cut and meander through a floodplain smothered in deep layers of soil that has been eroded from the uplands. Those elevated floodplains also increase the height of floodwaters.
What's more, many streams have been dredged and straightened into virtual canals. This accelerates the flow of water, carving the channel deeper. The speed and amount of the water from channelized segments increases downstream flooding.
Channelization also reduces the diversity of stream habitat for fish and other aquatic organisms. What's left after channelization amounts to a biological desert, Siegwarth said. There may be nothing except a barren sandbar or sterile mud flat. The stream valley bears little resemblance to the landscape of 150 years ago.
Contrast that with a natural stream's diverse community of gravel, riffles, rocky bottoms, snags, cut-banks, pools, meandering channels, and backwater shallows. It's a rich habitat for invertebrates and plant life, and for the fish, wading birds, small animals, and other creatures that feed on them. These organisms also help cleanse the water flowing through the system. Fortunately, some farmers have started to restore those conditions by planting buffers along streams, and by incorporating strips of prairie vegetation into crop fields.
While a casual observer may see only reflections on the river's surface, “this is actually an unrecognized thriving biotic world living under the water,” Siegwarth said, “an unseen, voiceless community of countless species that have no line on the economic spreadsheet.” The environmental benefits – from purifying water to restoring groundwater to esthetics to nurturing wildlife – often are ignored, as well.
If a bulldozer moved through a community, destroying houses, trees, neighborhoods, streets, and utilities, citizens would demand a halt to the destruction, Siegwarth said. But when we destroy a stream community with channelization, or with excessive siltation, people don't seem to notice – except for anglers who wonder why they can't catch many fish.
Siegwarth worried that high corn and soybean prices will continue to entice farmers to plant more annual crops, accelerating runoff and erosion, reducing stream health – and exacerbating floods.
When the oil well blow-out in 2010 spewed nearly 5 million barrels of crude oil into the Gulf of Mexico, there was an international uproar, Siegwarth noted. Fishermen, tourists, boaters, wildlife biologists, and others feared horrific damage to the Gulf ecosystem and coastal wetlands.
Yet that amount of oil seems almost trivial, compared with the 14 billion barrels of topsoil that Siegwarth estimated erode off Iowa farms and into our rivers each year. That rate of erosion is based on the five tons per acre that most farmers consider “acceptable.”
“This massive amount of annual soil loss goes seemingly unnoticed by the media and the public,” Siegwarth said, “but it's far more catastrophic to an entire river system and the Gulf than the more publicized BP oil spill.”
The river is a messenger, Siegwarth said. It's an ultimate barometer that reflects past and present land use – and abuse – within the entire watershed. When we understand the river's message, perhaps we will be more careful in how we treat the watershed.
Read the first, second and third articles in this series.
Originally published by the Cedar River Watershed Project
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