Earth Notes: Natural Channel Design

Jan 30, 2019

Healthy streams perform essential work, soaking up energy from floods and melting snowpack. But sometimes we’ve made deliberate or unintentional changes to streams that hamper their ability to fulfill their natural functions.

Wenima project before
Credit Natural Channel Design

That’s when companies like Flagstaff-based Natural Channel Design and Fred Phillips Consulting can lend Mother Nature a restorative hand. They start by referencing a section of stream that’s working well. Then, they estimate the size of floodplain, the active channel, and vegetation along the banks to determine what’s needed to restore a degraded reach.

Wenima project after
Credit D. Cagle

The stream flowing through old farm fields in the Wenima Wildlife Area, along the Little Colorado River near Springerville, Ariz., had been straightened and was eroding too much sediment from its banks.

A stream design team rebuilt the channel meanders with dirt, brush, and logs, mimicking the original shape and size—and with gentle curving bends. That’s helped shift the erosive stresses back to the center of the stream, recreating a natural floodplain.

Another project focuses on an eight-mile stretch of the Virgin River in southern Utah grazed by cattle. Vegetation that stabilized the stream banks has been eaten away, and floods have eroded the sides and created a braided channel across the entire valley.

Once grazing can be reduced or eliminated, a team will plant native vegetation where the channel should be. Those plantings will help “train” the stream to shift back to its original narrow thread. Well-aerated riffles and meanders with pools will also help bring back healthy aquatic invertebrates and fish.  

It turns out nature knows what she’s doing—and provides an excellent guide.