"It's sometimes intentionally used for erosion control, but it does its job too well. When planted along riverbanks it'll take over," said Jennifer McCard, a Kenai Watershed Forum watershed scientist.
The grass - which can grow to more than six feet tall and in thick clusters - can suppress native vegetation, and the sturdy, hollow stems of the grass can make juvenile, as well as adult, salmon passage difficult to impossible.
"It will actually grow right in the channels, but the old grass can also build up and block off channels, just like a beaver dam," McCard said.
In addition to threatening salmon, the stems grow too densely to provide adequate cover for small stream-side mammals and birds such as waterfowl. Moose and most other herbivore species won't eat the grass.
As a major threat to the local wetland ecosystem, the Kenai Watershed Forum is pursuing ways to get rid of the grass, but once established, it can be difficult to eradicate.
"One of the goals of the Kenai Watershed Forum is to evaluate the health of the watershed and that means keeping streams open so salmon can have as much habitat as possible," McCard said.
The Kenai Watershed Forum applied for, and received, $45,000 from an Alaska Department of Fish and Game grant, according to McCard, and now that money is being put to use in a multiyear project to remove the wetland weeds from two locations.
"We've targeted high priority sites on the Kenai River, one at Bing's Landing and the other at Beaver Creek," McCard said.
In both locations the grass was intentionally planted, but it has displaced native vegetation.
"There's thick patches of it there, and there's the potential for the seeds to travel downriver and start a new patch," McCard said.
However, with the grass growing so close to the river, herbicides are not a desirable option, so McCard said a technique called "tarping" is being attempted.
"It's experimental, but we're trying to see what works," McCard said.
The process involved weed-whacking the grass down to the ground, and then placing large swaths of black tarp over the areas to cover them and block out sunlight. Wood chips also have been added over the tarps, but strictly for aesthetic purposes.
"It could take up to three years of the tarps in place to ensure the roots die, too. Then we'll go in and revegetate the area with a native grass," McCard said.
If the project proves successful, the Kenai Watershed Forum will begin targeting other areas where the grass is known to occur.
"We're at a crossroads. The grass has taken over in some places, but we still have the opportunity to catch it," McCard said.