Erosion
Erosion is perhaps the greatest threat to the existence of the Las Vegas Wash, and therefore is one of the biggest challenges being addressed by the Las Vegas Wash Coordination Committee.
Increased erosion results in fewer wetlands to polish the water before it enters Lake Mead. Wetlands are often considered "kidneys of the landscape" because of their role in filtering the effects of surrounding land use.
In addition to the potential effects on water quality, a decrease in wetlands also has an effect on habitat in the Las Vegas Wash.
In the early part of this century, the area known as the Las Vegas Wash was nothing more than a slow trickle of water leaving the valley to join the Colorado River. For the most part, the Wash was an almost dry desert wash channel that would only flow during rainstorms. As the Las Vegas Valley grew, the Wash served as a natural channel for the urban flows leaving the valley. Highly treated effluent, shallow ground water, urban runoff and intermittent storm flows would all channel through the Wash and out into Las Vegas Bay at Lake Mead.
With increased amounts of water flowing through it, the Wash became excellent wetland habitat as thousands of acres of desert soil were transformed into wet marshy wetland soil. As cattails and reeds took root and grew, the once dry desert land became lush wetlands.
As the valley continued to urbanize, the flows of water continued to increase and the same process that created the wetlands began to erode the Wash channel. At first, the Wash channel began to cut a little deeper into the ground and some of the wetland areas began to drain. As time went on, the channel cut deeper and wider, which allowed more wetland area to dry out and lose its vegetation. Little by little, the soil and rock that made up the Las Vegas Wash channel eroded away, and the Wash became severely eroded and deeply channelized.
As erosion continued, the wetland area that once covered more than 2,000 acres in the 1970s dwindled to less than 400 acres in the 1990s. In some areas of the Wash, the channel is as much as 40 feet lower and 300 feet wider than it was 15 years ago.
If we are to preserve the Las Vegas Wash and restore the wetlands in and around the Wash, our greatest challenge will be to slow down the erosion and headcutting, through stabilization efforts, that has occurred over the last 25 years.