A new study published by The Journal of Hydrometeorology reveals that rapid urbanization and changing rainfall patterns are altering the strength and seasonality of flooding in the desert region.
Desert Research Institute, the Clark County Regional Flood Control District, the University of Wisconsin-Madison, and Guangdong University of Technology researched examined a changing flood regime and have shown an increase in flood intensity since the 1950s. An “abrupt” shift occurred in the mid-1990s, coinciding with more housing construction.
They also identified a shift in flood seasonality. Storms and subsequent floods now occur with more frequency in winter, a sharp contrast with the historical monsoon season in summer.
To mitigate the rising flooding risk from impervious surfaces and intense storms, Clark County Regional Flood Control District built a complex series of storm ditches, culverts and basins to channel water away from populated areas and toward Lake Mead.
Guo Yu, Ph.D., lead author of the study and a hydrologist at DRI said, that understanding the change and physical mechanisms driving is expected to help water managers and the public determine whether the pattern will continue into the future, given climate and land use changes here.”
Las Vegas is one of the fastest growing metropolitan regions in the country. In 1950, the population was fewer than 35 thousand people. Along the valley’s western rim, Summerlin was the top-selling master-planned community in the nation for much of the 1990s. By 2020, the region had 2.6 million residents.
Two distinct flood seasons characterize the Southwest region: winter floods produced by atmospheric rivers and summer floods linked to the North American monsoon. Since 1950, daily rainfall amounts have increased in winter and decreased in the summer months.
Yu said, “Warmer sea surface temperatures on the Pacific coast will cause more atmospheric rivers... And when (ARs) are positioned to bypass the Sierra Nevada mountains, they will very likely hit Las Vegas and cause severe winter rainfall and floods.”