December 5, 2019

Creek maintenance is unlike assessment - Daily Leader Extra : Editorials

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Creek maintenance is unlike assessment

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Posted: Wednesday, November 6, 2019 3:58 pm

We saw a backhoe working on Memorial Creek Tuesday and started thinking about upcoming maintenance.

We've written about the full-scale assessment project being pursued by the city and county to mitigate flooding on Memorial and Silver creeks, a necessary step in preventing future events the same magnitude as we had in September.

The problem of managing waterflows is more complex than it seems and requires a study of the entire watershed to make improvements. But that topic is completely separate from the annual creekbed maintenance necessary to maintain flows.

Because our creeks start small in farm fields outside the city and accumulate into larger creeks and lakes, there is always soil, sand and other materials coming into the waterways. In high water years, the accumulation is even larger.

An observer can see a number of the "sandbanks" in the middle of the creeks, and those could very well cause problems in spring runoff when the winter snow melts. They can be removed now, while the soil temperature is above freezing, but will be inaccessible when the creeks freeze solid.

There are also sandbanks and other accumulations under the surface of the water in creeks, sloughs and lakes. There is a large "plume" of silt, for example, where water enters Lake Madison at the northwest end. Those could only be removed by dredging, a more costly and controversial process.

Annual creek maintenance needs to remove vegetation as well as sand and silt, anywhere from overgrown weeds to small trees. Vegetation can alter the flow of a creek and damage the historic rock walls on Memorial Creek.

Annual creek maintenance sometimes requires more time and equipment than city street crews can provide, so the city engages independent contractors to help.

We're glad to see the process started and would expect to see plenty more work done in this tight window of time before work is no longer able to be done.

-- Jon M. Hunter