Alfalfa sprouts reveal how meandering rivers form on Earth

Written by: Super Admin
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Washington, October 6 (ANI): In a new study, experiments involving alfalfa sprouts are revealing some of the necessary conditions for formation of meandering rivers on Earth.

Researchers at the University of California, Berkeley, US, are carrying out the study.

Sinuous, meandering streams produce diverse and wildlife-rich habitats and are the aim of many river restoration efforts, but until now, the bank, water flow and sediment conditions required to form and maintain meanders have been largely a matter of speculation.

Now, a University of California, Berkeley, study reports the first experimental creation of meanders in a flume - a scaled down representation of a natural channel using alfalfa sprouts to represent vegetated stream banks.

These experiments reveal some of the necessary conditions for formation of meanders on Earth and throughout the solar system.

According to UC Berkeley graduate student Christian Braudrick, a former environmental consultant, "Our flume model will now let us do investigations that we can't do in the field but, until now, haven't been able to do in the lab, finally linking experiment with the geomorphology we see in nature."

Snaking meanders typically form in low-sloping valleys where, over the years, they wander across their floodplain, creating new floodplain deposits and leaving behind tree-lined sloughs, chutes and oxbow lakes that team with fish, birds, mammals and reptiles.

Braudrick created a successful laboratory model of a gravel-bed stream by finding the right material to reinforce the banks - alfalfa sprouts - and the right material to represent fine sediment - 0.25-0.42-millimeter lightweight plastic particles.

He used sand to represent gravel.

Working in a gently-sloping, 6.1x17-meter box filled with sand and planted with alfalfa sprouts, he carved a 40-cm wide channel with a single bend at the top, turned on the water, introduced plastic and sand and let the sproutscape rearrange itself over a total of 136 hours.

"We found that you need enough vegetation on the outer bank to slow down erosion and let the bars grow on the inner bank; otherwise, the stream cuts through the point bars and creates a braided river," Braudrick said.

Key to the experiment's success was the use of alfalfa sprouts, which was suggested by related experiments at the University of Minnesota, headquarters of the National Center for Earth-Surface Dynamics, of which UC Berkeley is a member.

As with trees and other vegetation along natural rivers, the roots of the alfalfa sprouts provide strength to the soil and, when exposed, protect the banks from the force of the water, preventing banks from washing away too quickly. (ANI)

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