Vegas valley battening down for monsoon season

Tuesday, June 28, 2005 | 9:51 a.m.

From July through September, Las Vegas Valley weather forecasters, emergency personnel and public works crews keep wary eyes on the skies.

They watch for any black clouds billowing over the western mountains, a sign that an afternoon thunderstorm may dump enough rain in a short enough period of time to turn city streets into rivers.

The Southwest's monsoon season runs from July 1 through the end of September. That's when a prevailing pattern of winds frequently sends moist air from the Gulf of California north over the southwestern states, triggering lightning, thunder and flash floods.

Since August 1960, 32 people have drowned in floodwaters created by heavy rains in the Las Vegas Valley, most of which came during the monsoon season, officials said.

Although flood control systems are improved every year, the burgeoning development of the valley has also contributed to the flooding as well. Urban growth with more rooftops and pavement increases runoff two to six times over the amount that would flow over -- and sink into -- natural terrain.

So far, forecasters said that this year it is hard to predict what this summer will bring, forecasters said.

"We really don't have a good indication yet," said meteorologist Andy Bailey of the National Weather Service office in Las Vegas.

But Kelly Redmond, a climatologist with the Western Regional Climate Center in Reno, said the latest climate projection for the next nine months calls for hotter than normal temperatures and lower rainfall than normal during the three monsoonal months. Researchers have noticed a weak link between wet winters and drier summers, Redmond said.

"Wet, snowy winters normally push the monsoon season later," Redmond said, referring to the fact that the Las Vegas Valley has just had its wettest winter on record while Northern Nevada's mountains enjoyed enough snow to extend the ski season.

Average annual rainfall for the Las Vegas Valley, measured by the National Weather Service at McCarran International Airport, is 4.49 inches. Already this year the valley has topped 5 inches, with most of that coming before the winter was over.

But local government officials aren't waiting for a rainy day to raise the awareness of Las Vegas Valley residents to the dangers of flash floods.

Las Vegas City Councilman Larry Brown, who serves on the board of directors of the Regional Flood Control District, announced July as Flash Flood Awareness Month at a city council meeting earlier this month, and the district is conducting a press conference today to try to spread the word that the flash flood season starts Friday.

"More than one-half of all flood-related deaths in Clark County are the result of people attempting to drive through flooded areas," Brown said.

The Regional Flood Control District will have completed 13 projects from June 2004 until July 2005 at a cost of roughly $74.4 million, according to district figures.

Another 18 projects are under construction with a price tag of $137.4 million.

The Flood Control District is preparing to break ground for a channel and debris basin at Fort Apache Road between Sunset and Russell Roads, the final piece to a $300 million flood control project, Flood Control District spokeswoman Betty Hollister said.

The Flood Control District is also planning a flood safety campaign outreach program to help residents become aware of the dangers of flash floods and prevent drownings.

For three weeks this summer, residents can log onto the Regional Flood Control District's Web site, ccrfcd.org, and submit ideas for a personalized license plate message about flood safety.

The winner will get his or her plate on a billboard for August and September, Hollister said.

Last year's winner, Dale Polinski of Henderson, submitted the winning entry, W8ITOUT (wait it out), a good piece of advice for Southern Nevada motorists, Hollister said.

"Never drive through water flowing across a road" because you never know the condition of the pavement -- if there is any -- underneath muddy waters, Hollister said.

Reports of 184 different floods have been recorded in Clark County dating back a century, Regional Flood Control District hydrologist Tim Sutko said.

The most recent severe one was on Aug. 19, 2003, when an intense thunderstorm dropped in excess of 2 inches of rainfall in roughly 90 minutes. The rain fell within a 50- to 60-square-mile area of northwestern Las Vegas. Some of the worst flooding occurred on Gowan Road, east of U.S. 95, pouring down Alexander, Craig and Lone Mountain roads. Damage to public property was estimated at $1.5 million with a similar damage amount estimated to private property.