From The Pueblo Chieftain (Matt Hildner):
Heather Messick, an employee of the project, said it is designed to stabilize the river’s banks and stem erosion, which increases sediment in the river. More sediment can alter the river’s channel, heat up water temperatures to the detriment of fish and change the riparian habitat as the river eats more of its unstable banks. Gone are banks that resembled cliff faces and stood as high as 14 feet over the river in spots. In their place are sloping banks that gradually push back to the flood plain.
The project also includes a series of rock barbs that jut into the river channel. The piles of rock push the river’s current into the center of the channel and away from the banks. It’s expected they will keep the banks in place until willows can spread.
The shrubs carry an added benefit of being the primary habitat for the southwestern willow flycatcher, an endangered species that makes its home along rivers in six other Southwestern states.
Unlike much of the Arkansas Valley, tamarisk invasion is not a threat to the exposed banks. Messick said researchers aren’t entirely sure why the invasive plant hasn’t taken root in the San Luis Valley, but hypotheses range from the valley’s cooler temperature to its higher altitude.
More Rio Grande River basin coverage here.