ASTANA - Friday, January 21, 2011 -
A mudslide that could destroy half of Almaty, Kazakhstan’s biggest city, is becoming likelier because of climate change, scientists say.
A report that a blue-ribbon panel of scientists prepared for the United Nations said the country’s winter temperatures have risen an average of 0.44 of a degree Celsius each decade since the mid-1930s.
The 3.3-degree increase over the past 75 years has melted much of the glacial ice in the Tien Shan and Alatau mountains surrounding Almaty, making the metropolitan area of 3.5 million people susceptible to a catastrophic slide, according to the report.
A mudslide of the size scientists are talking about would not only be a humanitarian disaster but a major blow to Kazakhstan’s economy because Almaty is the nation’s commercial center.
The reason the city is susceptible to a big slide is that water from melting glaciers has seeped into the soil on the slopes below the ice, according to the study prepared for the U.N. Framework for Climate Change. The report was completed last year but has received little international attention.
Mudslides occur when earth becomes so saturated with water that it gives way, experts say.
A fast-moving triggering event often causes the ground to reach the saturation point with little or no warning.
Scientists see two possible triggering events for a big slide in the Almaty area. One is heavy rain in the mountains. Another is a massive chunk of ice toppling into a glacial lake, causing water to shoot up and out of the lake, then rush downhill in a flash flood.
The experts who produced the glacier and mudslide sections of the report to the United Nations were B.S. Stepanov and R.K. Yaphyazova of the Kazakhstan Meteorological Service and I.V. Seversky of the Kazakhstan Geography Institute. Dozens of additional scientists worked on sections dealing with other climate-related issues.
The report noted that the mountainous areas of southeastern Kazakhstan were prone to mudslides even before an increase in the country’s greenhouse gases began raising temperatures three-quarters of a century ago.
In fact, a mudslide destroyed much of Almaty in 1921, claiming 500 of the city’s 45,000 residents.
The slide sent an estimated 10 million cubic yards of debris cascading onto Almaty, two-thirds of it mud and one-third rock, including boulders several yards in diameter. It roared down the slopes at an incredible 900 cubic yards per second, according to estimates.
Given Almaty’s current size, a catastrophic mudslide would likely claim many more lives than in 1921 – perhaps tens of thousands.
A visible sign of today’s increased mudslide threat is an increase in the number of alpine lakes that glaciers have carved out on the northern side of the Ileisky Alatau Mountains the past four decades, according to the report to the United Nations.
The area had 10 sizable lakes in the 1960s. The figure quadrupled to 41 by 1980, then jumped to 60 in 1990.
Melting glacial ice created landslides that scoured holes in the earth. Additional melting filled the holes, transforming them into lakes.
Heavy rain or a huge chunk of ice that breaks off a glacier could cause any of the lakes to overflow, triggering a mudslide.
“The biggest threat (of a mudslide) comes from the glacial lakes located near Almaty,” said a person familiar with the danger who asked not to be identified.
She considers the Number One threat to be 11,800-foot-high Lake Mametova in the Zailyskyi Alatau Mountains.
It’s only a couple of miles from Almaty, with one guidebook describing it as just “above the heads of Almaty residents.”
Mametova’s volume has quadrupled from 70,000 cubic yards in 1970 to 280,000 today.
With the 1921 mudslide in mind, the government built a dam across the Malaya Almatinka River valley above Almaty in the late 1960s and early 1970s – not for flood control but for mudslide control.
Visitors can grasp immediately that the dam was not designed for holding back water because pipes were built into the structure to let the river continue wending its way downhill.
The river descends steeply from the mountains through a narrow canyon, factors that ensure that mudslides roar down the valley at breakneck speed.
The dam, just below the famed Medeu Skating Rink that will be part of the Asian Winter Games, was completed in 1972, one year before a sizable mudslide. It did what it was supposed to do in that instance – contain the slide.
But glacial melting could lead to a mudslide so large that the dam is unable to contain it, scientists warned in the report to the United Nations.
A slide “exceeding the capacity of the mudflow reservoir in the Medeu” area would destroy most of Almaty, the scientists concluded.