Weather Window | Pineapple Express dents drought
February 19, 2014
TAHOE/TRUCKEE, Calif. — Heavy rain and snow in the past week has not mitigated the severe drought conditions in northern California, but it pumped up Lake Tahoe water levels and gave a much needed boost to Tahoe resorts which had been limping along on life support.
Commonly known as a "Pineapple Express" storm, the National Weather Service now refers to them as "atmospheric river events" when describing a subtropical moisture surge from the Pacific Ocean. During the four-day storm, Tahoe City picked up more than six inches of rain, while the upper mountain at Squaw Valley was hammered with five to six feet of new snow.
The danger of Truckee River flooding never materialized as snow levels failed to rise as high as predicted, which kept much of the precipitation as snow above 7,000 to 7,500 feet.
The Tahoe Sierra isn't always so fortunate when the Pineapple Express rolls in.
In February 1986, one of the greatest and most widespread floods on record devastated California and Nevada with phenomenal amounts of precipitation. On Feb. 11, 1986, a slow-moving storm laden with abundant moisture impacted Northern California for 10 days. Unprecedented amounts of rain pounded the region. The heaviest 24-hour rainfall ever recorded in the Central Valley, 17.60 inches, occurred on Feb. 17, 1986, at Four Trees in the Feather River Basin. At Calistoga, 29 inches of rain in 10 days created a once-in-a-thousand-year rainfall event.
The overwhelming floodwaters tore bridges from their foundations and punched through levees. Thirteen thousand homes and businesses were damaged or destroyed. Thirteen people died and 96 were injured. As levees burst and dams failed, more than 50,000 people fled their homes in fear. Damage was estimated at $500 million.
The lowlands certainly suffered, but the storm also delivered a potent punch to the Sierra and Western Nevada. Rainfall totals were incredible. In just nine days nearly 10 inches of rain drenched Carson City, setting a new monthly precipitation record. Not bad for a city that receives less than 12 inches in an average year. Due to the storm's tropical origins, snow levels fluctuated between 7,000 and 8,000 feet.
Between Feb. 11 and Feb. 20 more than 17 inches of rain fell at the Truckee Ranger Station. Water-logged observers at Blue Canyon on the Sierra west slope tallied nearly 34 inches of rain in the same 10 days. Above 8,000 feet storm total estimates ranged from 15 to 20 feet of new snow with 20-30 inches of water content.
Disappointed ski resort officials complained that the weather improved slope conditions, but due to negative media coverage of the storm, the economically important President's weekend crowds were smaller than usual. The media didn't have to spin a negative message; the storm was brutal.
Slushy snow clogged Donner Pass and Echo Summit delaying thousands of frustrated holiday travelers. Sturdy pines collapsed under the sodden snow load taking power lines with them. Scattered blackouts plagued the region. An avalanche 300 yards wide blasted through the Third Creek canyon above Incline Village, Nev. Trees 200-feet high were snapped at their base. The slide wiped out a utility road and a municipal water line, but damaged no homes.
Despite an extensive flood control system, millions of gallons of water raced into the Truckee River. Shortsighted and destructive logging and grazing practices over the last 100 years intensified the runoff. The loss of water-absorbing plants and trees coupled with accelerated runoff from roads, parking lots and rooftop areas transformed the normally peaceful Truckee River into a raging torrent.
Downstream communities prepared for the worst. In the Carson Valley hundreds were evacuated. Reno became virtually isolated when floodwaters surrounded the "Biggest Little City" and cut off all roads except Interstate 80 east. Riverfront casinos in downtown Reno sandbagged their buildings, but hundreds of stranded tourists kept the slot machines ringing steadily.
On Feb. 19, the Truckee River literally exploded. A 12-inch natural gas pipeline underneath the river ruptured near Wadsworth, Nev. A plume of escaping gas shot 15 feet into the sky through the muddy torrent. About 42,300 residences and businesses from Fallon to Lake Tahoe were without gas for heating and cooking for more than a week.
The storm finally broke on Feb. 21.
In Nevada the flood caused $17 million in damage and five western counties in the Silver State were declared Federal Disaster Areas. The historic series of storms during Feb. 1986 provided many painful lessons for river control and water management in both California and Nevada. Due to the 1986 flood, Folsom Dam operators now leave twice the empty space for water storage at the beginning of each rainy season. During the recent storm, Folsom reservoir rose 20 feet in four days. Managers are also much more aggressive at releasing excess water sooner than later and more of it.
Tahoe historian Mark McLaughlin is a nationally published author and professional speaker. His award-winning books are available at local stores or at http://www.thestormking.com. You can reach him at firstname.lastname@example.org. Check out his blog: http://www.tahoenuggets.com.