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What is the Wash?
Channel Stabilization

The Issues

Over the past 40 years, erosion has destabilized the Wash channel and caused increased sedimentation in Lake Mead. The Comprehensive Adaptive Management Plan developed by the Las Vegas Wash Coordination Committee (LVWCC) identifies stabilizing the Wash as one of three key initial steps needed for long-term management of the Las Vegas Wash. As a result, the LVWCC has developed the Las Vegas Wash Capital Improvements Plan, which will help to stabilize the channel over the years.

Lower Narrows Weir
Lower Narrows Weir

One way to deal with erosion is by placing erosion control structures (which are also known as grade control structures or weirs) throughout the Wash. As we succeed in stabilizing sections of the channel, we develop additional riparian and wetland habitat. The erosion control structures help slow the water, creating a pond behind the structures in which wetland plants can establish. Weir construction activities also clear acres of invasive plants such as tamarisk from the banks of the Wash. These cleared areas are then revegetated with native wetland, riparian, and upland species.

Upper Diversion Weir
Upper Diversion Weir

Achieving Equilibrium

Addressing conditions such as: increasing and variable daily flows, highly erodible soils, water quality concerns, the need to protect wildlife habitat, and other environmental concerns present formidable challenges to controlling erosion in the Wash. However, efforts are currently under way to promote channel stabilization by decreasing channel bed downcutting, reducing stream bank erosion, armoring the channel with vegetation, balancing sediment transport and enhancing the ecosystem.

TABLE 1
GENERAL LAS VEGAS WASH DESIGN GOALS

Present Conditions

  • Variable, changing flows
  • 0.20 to 0.80 percent channel slope
  • 20 active headcuts
  • Flood velocities at 10 to 20 feet per second
  • Little channel or bed protection
  • Highly variable sediment carrying capacity

Stable Conditions

  • Predictable base flow ranges
  • 0.05 percent to 0.3 percent channel slopes
  • Stable channel without headcutting erosion
  • Flood velocities below 10 feet per second
  • Stable channel sideslopes
  • The sediment amount entering the system is equal to the amount of sediment leaving the system

Las Vegas Wash Project Coordination Team • 100 City Parkway, Suite 700 • Las Vegas, NV 89106 • (702) 822-3300