A public meeting was held Tuesday evening to hear a presentation and input on a bank stabilization project. Grant County is working on it to prevent a bank of the Gila River breaching and flooding nearby homes, as well as marooning the residents by destroying the one road in and out of the area.

Grant County Planner Anthony Gutierrez explained the project is near Iron Bridge and on a roadway that serves 20 to 30 residences.

“With this project, in addition to stabilizing the bank of the river, we are considering the endangered species in and near the river and trying to improve the riparian habitat,” Gutierrez said. “In speaking with the County Commission, the commissioners want to create a model and use it for other flood control projects, by trying to do restoration and habitat improvement.”

David Maxwell and David Trushaw of Engineers Inc. have developed the options. Tammy Miller and Mariana Padilla of Parametrix have been doing the environmental assessment, which includes planting and restoration.

“There are other places on the Gila River where we can use our approach,” Gutierrez said.

Trushaw gave a presentation, with maps and explanations of options.

“With further erosion of the bank in question, the river could break through the bank, damage properties and remove access,” Trushaw said.

He also gave a history of the stretch of river. In 1916, the Iron Bridge was constructed. In the late 1960s to early 1970s, a new bridge was built on U.S. 180 West.

From 1980 to the mid-1990s, the river flows redirected and began causing erosion on the west bank, in addition to stream migration.

“The Gila River tends toward stability,” Trushaw said, “and geomorphologic and hydrologic studies in the early 2000s by the Bureau of Reclamation show the main channel to be the most stable. The west bank between the 180 bridge and the Iron Bridge is the least stable part of the river on this stretch.”

The design criteria include flood protection and the 100-year floodplain, bank stabilization, and habitat and riparian improvement.

Several alternatives were considered, including riprap with two- to three-foot diameter rocks; brush revetments and live staking of willows; and weirs to create riffles.

Vegetation in the floodplain slows flows.

“We are proposing cross-vane weirs and stream barbs to help provide bank stabilization and fish habitat,” Trushaw said.

Three options were developed, with the first option of redirecting the steam to the old channel being the most costly. The second option is to armor the existing bank, which is the cheapest, but does not provide flood protection. The third option is relocate the stream, put in meanders and cross-vane weirs.

“The option chosen is a hybrid,” Trushaw said. “We would relocate the stream to it previous location, protect the bank, and put in cross-vane weirs and brush revetments, as well as a backwater to provide an oxbow lake.”

The existing stretch of river is 2,570 feet long; the proposed would be 1.750 feet. The slope would increase from .26 percent to .37 percent, with 800 feet of stabilized bank, creating a wider and shallower stream.

Miller said the process would require a nationwide Permit 27; an authorized relocation of a non-tidal flow; and compliance with endangered species and historic preservation regulations.

Endangered species include the loach minnow the spikedace, and the southwestern willow flycatcher. Also under consideration are the common Blackhawk and the Arizona toad.

“The proposal provides habitat similar to what is existing and would create improved habitat for the flycatcher,” Miller said. “The backwater wetland would be for juvenile fish and the Arizona toad.”

Although 819 linear feet of stream would be lost in the proposal, there would be a gain of about one acre of surface mitigation.

The plan includes five years of monitoring from the established baseline conditions. If needed, adaptive management would take place.

Miller noted that the team has met with regulating agencies at least three times, so they are on board with what is planned.

Al Schneberger, a resident of the area, asked about the 100-year flood plain. Trushaw said it was determined by the Federal Emergency Management Administration.

“It is awesome to stand on the bank and watch a flood flow,” Schneberger said. “Talking about habitat and restoration seems trivial when you see huge cottonwood trunks going down the river, and the ground is wiped to mud.”

Gutierrez said in the case of a rain on snowpack, as much as 35,000 cubic feet a second could be running. “That will be part of the contingency plan.”

“We want to stabilize the bank,” Gutierrez said. “We have an emergency permit to stabilize the embankment in case of a flood, before this project is complete.

“We've been working with the regulatory agencies to adapt our design, using what has worked in other places,” he continued. “We're trying to create a successful plan.”

Trushaw said the most important part is keeping the river away from the west bank.

J.T. Hollimon, area resident, said the only way the project will work is to put the river back in its old channel.

“Two- and three-foot rocks will almost float in a flood,” he said. “I'd say six-foot rocks are needed.”

Gutierrez said an upstream levee is causing the river to turn and change direction. “We're working on a happy medium to stabilize the bank of the road and will do rechannelization.”

Hollimon said Gabion baskets were put 12-feet below the water, but the “gravelly stuff moves, and the baskets settle. You need big rock.”

Gutierrez said the reason for putting in brush revetments is to slow down the water before it hits the hard face.

Hollimon opined that willows would stay where they are planted, but “cottonwoods are a waste.”

Ellen Soles, a resident of the area and the creator of the map showing the different channels of the river over the years, asked where the project begins and ends.

Trushaw said, because the project is still in its preliminary design, the locations have not been finalized. “The top of the meander is just upstream of Iron Bridge.”

“We will try to utilize the channel at the bar and use what is existing,” Gutierrez said.

Soles asked if the wetland at the lower curve would simply allow the existing wetland to remain.

Miller confirmed that it would.

Soles also asked where the borrow dirt for fill would come from.

Trushaw said the only place where much fill would be required would be where the river is being rechanneled.

“We may also add some fill where we are armoring the bank just upstream of Iron Bridge,” Gutierrez said.

Soles asked about the reasoning for a wider and shallower river.

“It's a better habitat for the fish,” Trushaw said.

Gutierrez said the team wants to get the final design done within the next few months, then the consultation with the U.S. Fish and Wildlife Service will take 135 days. “We want to submit the design to the U.S. Army Corps of Engineers by March 2012, and we hope to construct it next winter.”

Kenny McCauley who has family living near the planned area asked where the county would get riprap in case of an emergency.

Gutierrez said it would be obtained from two sources from each side of the river. He cautioned that the emergency permit might not be as good as it seems, because “we can't do anything until there is an event.”

“If it does wash out,” McCauley pointed out, “there are people from toddlers to the elderly who won't be able to get out. How soon would they be able to get out?”

Soles asked what triggers an emergency.

“The County Commission can deem it an emergency, and then the governor has to concur,” Gutierrez said. “The Corps is already aware of the possibility, so a couple of phone calls will get things going.”

To conclude, Gutierrez said the county wants a model project using methods that have worked in other places.