Sediment choking out wildlife in the Kankakee River

June 1, 2008

“Nothing grows in a desert,” J.R. Black said. He was referring to the deep sand now moving farther down the Kankakee River’s main channel.

Sand — and a finer wave of silt — compose the two major sediments found in the river system. “For the most part the sand is our problem,” Black said. “It settles out quickly and covers the river bottom. The silt mainly washes on down river.”

Now large portions of the Kankakee’s natural bedrock bottom are covered by sweeps of sandy sediments along the upper river in Indiana to the dam at Kankakee. Over the past few months a dramatic increase in sandy deposits have appeared downstream from the dam all the way through the Kankakee River State Park.

The livelihood of a river depends on its smallest creatures, aquatic insects and invertebrates living in the shelter of river bottom rocks and crevasses. And now people like Black fear the sand is choking off this foundation of the river ecosystem.

“The sand fills in the rocky riffles on the bottom,” Black said. “Small fish eat the bugs that live on the bottom and bigger fish eat the smaller fish.” This cycle is the river’s food web.

“There are all kinds of changes going on in Six Mile Pool,” Bill White, a river researcher with the Illinois State Water Survey at Peoria, said about the portion of the river in the city Kankakee. White said more work is needed to determine exactly what is happening on the Kankakee. “We are very concerned about the fact that there is more sediment moving along the river and that there is still more work that needs to be done.”

The problem is funding from traditional sources for such research is drying up.

“The state doesn’t have the money for the work we need to do. We are trying to define projects that can get funding from the (Army) Corps of Engineers,” said White, who has been working on projects for both the Kankakee and Illinois rivers.

Corps officials say they are having to prioritize which projects get precedence and the Kankakee River basin falls short of the top of that list.

“Six Mile Pool is almost full with sediments after years of building up behind the dam,” said Misganaw Demissie, director of ISWS’ Center for Watershed Science in Champaign.

“For years the dam was holding that sand back,” Demissie said. “More sand will go over the dam as time goes by. In major floods, like we saw earlier this year, there can be a lot of sand movement.”

While the sand can create dead zones in the river; suspended sediments, flowing mostly out of the Iroquois, pose different problems for the Illinois River.

The Iroquois ranks among the third highest group of rivers dumping sediments into the Illinois’ main channel, according to water survey studies done between 1981 and 2000. Larger tributaries such as the Spoon and LaMoine rivers contribute the most sediment.

Still the Iroquois carries nearly twice the load of suspended sediments that the Kankakee does, according to studies by the state water survey.

Overall most of the suspended sediments from the Kankakee basin end up in the Illinois’ Peoria and Dresden pools, where an estimated 60,000 acres of side channels and backwater lakes have filled in, according to the Illinois Environmental Council.

Some areas “have become so shallow that they’ve lost almost all value for fish, wildlife or recreation,” said Rob Kanter, who writes a monthly Environmental Almanac blog for the Environmental Council. “These areas were formerly six to eight feet deep, but now average less than 18 inches.”

Ironically, while sediment buildup is a serious threat to both the Kankakee and Illinois rivers, it is the exactly what many believe may ultimately reverse the loss of vital wetlands and estuaries along the Louisiana Gulf Coast.

Written by fandw08 · Filed Under Environmental News, Fishing