LANDSLIDES

In some areas of Kyrgyzstan, landslides and mudslides do occur. They have demolished buildings, and closed roads. Although visitors are unlikely to be involved in a landslide - they may occur - especially in periods of unusually heavy rainfall.

The weather in 2003 was not typical. There was been a lot of rain and unseasonably late snow — we even had a «White Easter» in Bishkek. More importantly, this has led to a number of landslides and avalanches.

The most serious was a landslide at Karatarik, a village of between 200 and 300 people in the Uzgen District, about 100 km east of Osh. Thirty eight people died including seventeen children.

Landslides and avalanches are not that unusual in the Kyrgyz Republic, although most of them concentrated at the rim of the Fergana Basin and after prolonged periods of bad weather. The occurrence of such events in this area is caused by complex interactions of geological, tectonic, geomorphological and hydro-meteorological factors.

The term landslide includes a wide range of ground movement, such as rock falls, deep failure of slopes, and shallow debris flows. Although gravity acting on an over steepened slope is the primary reason for a landslide, there are other contributing factors:

• erosion by rivers, glaciers, or ocean waves create oversteepened slopes
  
• rock and soil slopes are weakened through saturation by snowmelt or heavy rains
  
• earthquakes create stresses that make weak slopes fail
  
• earthquakes of magnitude 4.0 and greater have been known to trigger landslides
  
• volcanic eruptions produce loose ash deposits, heavy rain, and debris flows
  
• excess weight from accumulation of rain or snow, stockpiling of rock or ore, from waste piles, or from man-made structures may stress weak slopes to failure and other structures
  

Slope material that become saturated with water may develop a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses, and cars, thus blocking bridges and tributaries causing flooding along its path.

Where do landslides occur?

Landslides can occur almost anywhere. Any area composed of very weak or fractured materials resting on a steep slope can, and will likely, experience landslides.

Although the physical cause of many landslides cannot be removed, geologic investigations, good engineering practices, and effective enforcement of land-use management regulations can reduce landslide hazards.

The following information has been downloaded from the United States Geological Survey Internet website: http://greenwood.cr.usgs.gov

Landslide hazards occur in many places around the world and include fast-moving debris flows, slow-moving landslides, and a variety of flows and slides initiating from volcanoes. Each year, these hazards cost billions of dollars and cause numerous fatalities and injuries. Awareness and education about these hazards is a first step toward reducing damaging effects.

Fast-moving Debris Flows

Debris flows start on steep slopes-slopes steep enough to make walking difficult. Once started, however, debris flows can even travel over gently sloping ground. The most hazardous areas are canyon bottoms, stream channels, areas near the outlets of canyons, and slopes excavated for buildings and roads.

• Debris flows (also referred to as mud-slides, mudflows, or debris avalanches) generally occur during intense rainfall on water-saturated soil. They usually start on steep hillsides as soil slumps or slides that liquefy and accelerate to speeds as great as 35 miles (56 km) per hour. Multiple debris flows that start high in canyons commonly funnel into channels. There, they merge, gain volume, and travel long distances from their source.
• Debris flows commonly begin in swales (depressions at the top of small gullies) on steep slopes, making areas downslope from swales particularly hazardous.
• Roadcuts and other altered or excavated areas of slopes are particularly susceptible to debris flows. Debris flows and other land-slides onto roadways are common during rainstorms, and often occur during milder rainfall conditions than those needed for debris flows on natural slopes.
• Areas where surface runoff is channeled, such as along roadways and below culverts, are common sites of debris flows and other landslides.

What Can You Do?

Prior to Intense Storms: If a heavy storm is forecast - try to become familiar with the land around you.

During Intense Storms:

1. Stay alert and stay awake! Many debris-flow fatalities occur when people are sleeping. Listen to a radio for warnings of intense rainfall. Be aware that intense short bursts of rain may be particularly dangerous, especially after longer periods of heavy rainfall and damp weather.

2. If you are in areas susceptible to landslides, consider leaving if it is safe to do so. Remember that driving during an intense storm is hazardous.

3. Listen for any unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together. A trickle of flowing or falling mud or debris may precede larger flows. If you are near a stream or channel, be alert for any sudden increase or decrease in water flow and for a change from clear to muddy water. Such changes may indicate debris flow activity upstream, so be prepared to move quickly. Don't delay! Save yourself, not your belongings.

4. Be especially alert when driving. Embankments along roadsides are particularly susceptible to landslides. Watch the road for collapsed pavement, mud, fallen rocks, and other indications of possible debris flows.

Areas that are generally prone to landslides:

• On existing old landslides
  
• On, or at the base of, slopes
  
• In, or at the base of, minor drainage hollows
  
• At the base or top of an old fill slope
  
• At the base or top of a steep cut slope
  
• Developed hillsides where leach field septic systems are used
  

Areas that are typically considered safe from landslides:

• On hard, nonjointed bedrock that has not moved in the past
  
• On relatively flat lying areas away from sudden changes in slope angle
  
• At the top or along the nose of ridges, set back from the tops of slopes
  

Features that might be noticed prior to major landsliding:

• Springs, seeps, or saturated ground in areas that have not typically been wet
  
• New cracks or unusual bulges in the ground, street pavements, or sidewalks
  
• Soil moving away from foundations
  
• Ancillary structures such as decks and patios tilting and (or) moving relative to the main house
  
• Tilting or cracking of concrete floors and foundations
  
• Broken water lines and other underground utilities
  
• Leaning telephone poles, trees, retaining walls, or fences
  
• Offset fence lines
  
• Sunken or down-dropped road beds
  
• Rapid increase in creek water levels, possibly accompanied by increased turbidity (soil con-tent)
  
• Sudden decrease in creek water levels though rain is still falling or just recently stopped
  
• Sticking doors and windows, and visible open spaces indicating jambs and frames out of plumb
  

What to do if you suspect imminent landslide danger:

1. Evacuate.

2. Contact the local authorities

3. Inform the neighbors.