Mohave County works to improve Beaver Dam Wash, protecting citizens and infrastructure

Mohave County works to improve Beaver Dam Wash, protecting citizens and infrastructure

Beaver Dam destruction and repair work - Upper right photo by David Bly, Desert Valley Times

The northeastern part of Mohave County has seen its fair share of high waters and flooding after storms drop buckets of rain.

In 2005, storm waters flowed into the Beaver Dam Wash, damaging the Highway 91 bridge, the Virgin River Domestic Wastewater Improvement District sewer system pipeline, and several homes in the Beaver Dam Estates community. Mohave County rapidly worked to construct a new bridge and the sewer lines were also repaired.

Five years later, in 2010, a series of heavy rainstorms brought continuous rain (more than 20 inches in one week) to the same area, resulting in significant flooding and threatening the safety and health of residents in the Beaver Dam and Littlefield areas. 

A high storm water flow in a tributary of the Virgin River caused considerable damage to both public and private properties. Eight homes washed away in the Beaver Dam Resort community and many more were flooded. Properties adjacent to the wash lost soil from the excessive storm water flow, creating a vertical cliff where their sloped backyards used to be.

The same storm damaged many roadways in the area and destroyed the local sewer system and its lift station near the Beaver Dam Resort community.

The Governor of Arizona declared a state of emergency thus freeing up money from the State Emergency Fund to aid in the response and recovery efforts.

Mohave County spent the next few years making repairs and improving the infrastructure.

“Mohave County, with the assistance of Federal Highway Administration, replaced the breached training dike; cleaned out the channel in the County right-of-way; cleaned up the debris around the piers of the bridge, removing dirt, dead vegetation, and the remains of two cars,” explains Nick Hont, Mohave County Development Services Director and Chief Flood Control District Engineer. “A damaged stream flow gauge was repaired and reinforced. A new radar sensor stream gauge was installed on the new bridge. A warning siren was installed to facilitate potential emergency evacuations in the future, among other projects.”

With more work needing to be done in the area, the Mohave County Flood Control District (MCFCD) applied for a Hazard Mitigation Grant for the Beaver Dam Wash Erosion Control Project from the State of Arizona in 2014.

The State Emergency Council approved the $934,663.80 grant and allocated $700,997.85 from the Emergency Fund. According to the cost-sharing requirements of Arizona disaster assistance, the applicant is responsible for 25 percent of the total amount; in this case, $233,665.95.

The Arizona Department of Emergency and Military Affairs (DEMA) serves as the administrative body for funding authorized by the Council. DEMA assigned Dennis Erickson, Public Assistance Project Specialist to work with MCFCD for the duration of the grant. A project specialist is the county’s link to DEMA. He or she is the person they go to with updates and to discuss any issues.

“I began my work with MCFCD by preparing a project worksheet describing the scope of work of the project. I traveled to Mohave County for a kick-off meeting and attended teleconferences,” Erickson said. “I stayed in touch with the project manager during construction for updates and when the project was completed, I traveled to Beaver Dam Wash and conducted the final inspection. Writing the final inspection report closed the project.”

The project’s overall scope of work was to mitigate the banks of the wash that flood regularly and cause damage to public and private infrastructure. The work included the development of a 40-foot-wide low flow channel in the wash and the creation of rock slope protection for the two communities along the river.

The work for the low flow channel cross section included removing excess vegetation and silt deposits before workers reshaped the 40-foot-wide channel bottom and slope sides.

Many steps went into creating the rock slope protection. First, construction workers excavated and installed a riprap launch pad (riprap is rock or other material used to protect shorelines against water and erosion) and slope protection. The final step in the slope protection was the construction of a structural berm (a raised barrier) to separate the river bed and the community.

While the project is complete, there is still work to do. Erickson notes that “Mohave County must perform annual maintenance on the channel to assure the siltation and vegetation does not change the flow past either community on its way to the Virgin River channel.”

The project highlighted the importance of partnership. Various state agencies, Mohave County departments, private contractors, and community members were all involved in different stages of the project.

“It was a beneficial project and went very well. It was completed on time and on budget,” said Hont. “The channel is working as planned and the County is pleased to be able to provide enhanced protection to property owners and grateful for the assistance and grant received from the State.”

A future goal for the area is that the National Resources Conservation Service of the US Department of Agriculture will be able to fund a 100-year wall through their Federal Watershed Protection program, Emergency Water Protection.

“Hazard mitigation is absolutely critical for emergency managers,” said Byron Steward, Mohave County Emergency Management Coordinator. “When viable mitigation projects in specific areas can be developed and implemented, often by partner agencies such as the Mohave County Flood Control District, the threats to life and property, and the material and economic impacts from disasters can be substantially reduced. The Beaver Dam Wash project is an excellent example of a cooperative local, county, and state effort to implement protective measures that will greatly mitigate future flood impacts in the Beaver Dam community.”