Invasive weeds make flooding worse
February 14, 2012
Flooding seems an odd topic to discuss in Nevada, the most arid state in the union, particularly when we are having such a dry winter. However, many of us have witnessed damaging floods including those where the Carson River wreaked havoc on communities along its banks from Alpine County to Fallon or where the Truckee River rampaged through Reno, Sparks and areas east. I often teach about the negative impacts of invasive weeds and now, according to the Weed Science Society of America, there is another reason to control noxious and invasive weeds. Since these alien invaders threaten and reduce native vegetation along rivers and streams, the ability of riparian areas to store water and prevent or reduce flooding is greatly impaired.
Riparian areas lie adjacent to rivers, streams and wetlands. Special adapted plants grow in these areas. Riparian vegetation in Nevada includes willows, poplars, sedges, rushes, cattails and many others. The roots of riparian vegetation are extremely good at stabilizing and holding banks next to waterways, preventing erosion and degradation of water quality and wildlife habitat. Healthy riparian areas full of native plants also store thousands of gallons of water per acre. They capture sediment and filter water that flows through them after a storm or when snow melts. Water retained in these areas reduces flooding risk.
Roots of invasive plants are usually not as dense as those of native plants and don’t do a good job of stabilizing soil. After storm events, increased water flows rip away banks and erode soil. When soil is stripped away, banks deteriorate, stream channels can shift and flooding potential increases. During periods of heavy runoff, flash floods are promoted.
Perennial pepperweed, also known as tall whitetop, is an example of a noxious invasive weed that is a significant problem along the Carson River. In fact, it is one of the most troublesome noxious weeds in Nevada. Although its deep roots may grow three to 10 or more feet long, they are brittle and don’t hold soil the way native plant roots do. In areas along the Carson River in Lyon County, hundreds of acres are covered with perennial pepperweed, with few native plants left.
The next time someone asks why controlling invasive weeds is important, you can say “because it helps reduce flooding.”
JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at firstname.lastname@example.org or 887-2252.
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