COUNCIL BLUFFS — Another victim of the 2011 Missouri River flood: trees.
The Iowa Department of Transportation plans to remove about 5,500 dead and dying trees along the river west of Interstate 29 from the Missouri state line to the Sioux City area, according to Mark Masteller, chief landscape architect for the department.
The largest concentration extends from northern Council Bluffs to U.S. Highway 30 near Missouri Valley, he said. Cottonwoods and elms make up the majority of trees to be removed.
Cottonwoods, along with silver maples and sycamores, are an intermediate species when it comes to water tolerance, said Lindsey Barney, a forester with the Iowa Department of Natural Resources based in Oakland, Iowa.
"They generally can withstand flooding for about one to three months," she said. "The roots need oxygen to survive, to complete the chemical process to make food and energy. If trees don't have oxygen, they can't do those processes."
She said that she has examined trees on private landowners' property along the river and that she has found intermediate trees holding up.
"Some are looking pretty good despite the fact they were in floodwaters for about four months," Barney said.
"I've been surprised by the initial symptoms of stress. Intermediary trees, in theory, they should not be able to survive. Right now, they're good. Hopefully the trees will be able to survive."
Green ash and black willow trees withstand flooding quite well, generally able to take more than three months of flood inundation without major damage, Barney said. Species that can tolerate little to no flooding include evergreens, shagbark hickory trees and walnut trees.
Masteller said the Iowa Department of Transportation plans to divide tree removal into about eight projects, with the bid-letting process happening in March and removal beginning in April. The estimated cost is about $150,000.
For future plantings, Masteller said, "I think our approach is to wait and see what's left after all is removed. We'll take into account areas that are flooded more — more susceptible (to flooding). We might avoid planting in some of those areas."
He added that they may change what species they plant.