Thursday, June 27, 2002 | 11:11 a.m.
It's strange to hear about a monsoon season in the desert, but in Southern Nevada, it doesn't rain -- it pours.
The Las Vegas Valley may only get an inch of rain from July to September, but it often drops down on the city in one massive thunderstorm -- turning streets into rivers and parking lots into lakes.
The Clark County Regional Flood Control District is already putting out warnings about the flash floods as the monsoon season begins next week, reminding residents that even in the current drought, flash floods can occur at the first sign of rainfall.
The district is also working hard to improve flood control in the county, reopening the Spencer Street Bridge Tuesday, which was washed out in July 1999, the most lasting and visible damage from that devastating flood. Work continues on the channel below that bridge in efforts to keep the Flamingo Wash from overflowing its banks there again.
The slope of the valley and the dry, desert soil add to the danger of flash floods, as flood control basins here have been known to rise 14 feet in only 14 minutes, Gale Fraser, general manager for the Regional Flood Control District, said.
"A half-inch of rain here, where back East it would be nothing, causes flooding," National Weather Service meteorologist Andrew Gorelow said.
The water runs off the dirt as if it were cement, he said.
"The soil here is almost impervious," Gorelow said. "The water just doesn't get soaked into the soil and it just runs off."
That runoff can create flash floods moving as fast as 30 miles an hour, Fraser said.
"The soil, the slope, the severe rainfalls -- it's all part of a formula that makes (floods) deadly and dangerous," he said.
The Regional Flood Control District has been combating the danger of flash flooding since its creation by the State Legislature in 1985, after a series of floods inundated the Las Vegas Valley in the 1980s. At that time there were only three detention basins in place to catch rainwater. Now there are 53 basins and about 280 miles of channels and storm drains throughout Clark County.
Sixteen projects were completed this year and 13 more are under construction, including a $36.2 million channel system to reduce flooding around Interstate 15 from Sahara Avenue to Alta Drive.
The value of such construction was proved in the July 8, 1999, flood, which was blamed for two deaths, swept away three mobile homes and drenched businesses, homes and a casino.
The disaster would have been worse if not for flood control elements already in place at the time, Fraser said.
As a result Clark County commissioners helped speed up future projects by securing additional money for projects. Most of the projects are paid for by a voter-approved quarter-cent sales tax added when the flood control district was formed.
The district, which works with the Nevada Department of Transportation, Regional Transportation Commission and local and county governments, is about halfway through completing the projects laid out in its master plan, Fraser said. He added that they would continue to add projects to the master plan as flood control technology improved.
"The improvements that we've put in the ground are here to protect generations to come," Fraser said.
Residents still must protect themselves, however.
"What's so critical now as the flood season begins, what's most important to tell the community is not to drive through flood areas and to be smart," Fraser said.
It only takes a few feet of water to make an SUV float, Fraser said.
Drivers should never drive across flooded roadways or around barricades, he said, nor let children or pets play near flood control channels or detention basins as flash floods can occur with little notice.
Protection also comes in the form of flood insurance, which more and more people are choosing to buy even though the risk of flooding is decreasing. Sales of flood insurance policies have increased 16 percent since 1999, rising to more than 6,800 policies and $1.2 billion, Mark Stevens, public affairs officer for the Federal Emergency Management Agency, said.
Homes and businesses in high-risk flood zones financed by loans are required by federal law to have flood insurance, Stevens said. The Regional Flood Control District, however, has cut the danger area in half in the past six years alone, moving close to 21,000 acres out of the federally identified FEMA flood zones.
The most important thing to remember, meteorologists and the flood control district say, is that a flash flood can happen with little notice.
"If things set up right on a certain day, all hell can break loose and you can't really predict it," Jim Harrison, National Weather Service meteorologist, said.
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