Southern Nevada Impacts Associated with Tropical Moisture from Hurricane Norbert (Invited Presentation)

Tropical moisture associated with Hurricane Norbert generated intense rainfall over large areas of Clark County in southern Nevada September 7-8, 2014. Significant impacts occurred September 8 across the Moapa Valley, which is approximately 45 miles northeast of downtown Las Vegas. The Moapa Valley stretches both north and south of Interstate 15 and includes the towns of Moapa, Glendale, Logandale and Overton, as well as the Moapa Paiute Indian Reservation. Rainfall amounts across this region ranged from 2.5 inches to 4.6 inches, measured from automatic rain gauges operated and maintained by the Clark County Regional Flood Control District. The National Weather Service WSR-88D estimated rainfall totals in excess of 6 inches for some locations outside of the rain gauge network.

Substantial runoff from this rainfall flowed through the Meadow Valley Wash, Weiser Wash, and the Muddy River, inundating and exceeding the capacity of the Interstate 15 drainage system. There was major damage to Interstate 15, which caused both north and south bound lanes to be completely washed away. The highway was closed for several days while transportation officials evaluated the damage and implemented repairs. Several earthen dams and levees were eroded and subsequently failed, resulting in evacuations and damage to infrastructure. This presentation will identify a few key components that contributed to such a high impact event. Societal and economic impacts across the Moapa Valley will be highlighted. National Weather Service Las Vegas tools, procedures, communication, and services will also be discussed.