Tamarisk Removal Mitigates Flood Damage

Tamarisk removal efforts along Southern Nevada’s Virgin River couldn’t have come at a better time for the rapidly growing communities of Mesquite and Bunkerville. Only a few months after treatments were completed, flooding struck both communities at 100-150 year levels.

Tamarisk, also known as salt cedar, has adversely modified the hydrology and flood regimes of riparian systems throughout the Southwest, and has in turn altered the fire regime. BLM tamarisk removal efforts near Bunkerville and Mesquite not only reduced the wildland urban interface (WUI) fire threat to these rapidly growing communities, but also achieved sustainable restoration of the fire regime and high-value riparian habitats. 

The photo at left shows a neighborhood adjacent to BLM land before vegetation treatment.

In areas where BLM had removed massive amounts of tamarisk, the Virgin River was allowed to mimic its historic flood pattern. Fire occurrence and acres burned within the project area have been reduced to zero, far ahead of schedule for for the long-term Healthy Forest Initiative project.

The highly dynamic project environment in Mesquite and Bunkerville required integrated treatment tactics and adaptive management. Crews treated more than 5,000 acres using mechanical, hand-cutting, herbicidal, seeding and prescribed pile burning techniques, and saw significant reestablishment of native plants. Multiple resources benefited directly, including threatened and endangered species.

The unexpected synergy between the tamarisk removal and the record flooding allowed far greater cost savings. Soils were flushed of the tamarisk salt crusts that are toxic to native riparian plants. Site productivity was increased by deposition of new silt soils. In place of flat, dry tamarisk monocultures, an array of diverse native riparian habitat types grew, including perched oxbows and flood-scoured gouges that today are groundwater fed lagoons. The new lagoons are beneficial to wildlife, including threatened and endangered animals as well as migratory bird species.

Some Mesquite residents credit the project with saving their homes from the 2005 flood, whose waters tamarisk would have otherwise deflected sideways into their homes.

The photo at right shows the same neighborhood during the flood.