From a Sandcastle to a Mudslide

For sure, everybody has built a sandcastle at some point in his or her life. Some were big, some were splendid and some were built with a lot of fantasy. However, what kept the castles together?

A sandcastle only consists of sand and water, but it is exactly the water that is important. The water is finely dispersed between the grains of sand and therefore able to build a thin film on the grains (surface tension), which holds them together and gives stability to the castle.

No Sandcastle Without Water!

If the sand was more or less dry (left picture) and without moisture, the exceptional stability and durability of the sandcastle could not be accomplished. That’s the reason, for example, why dry dessert sand is blown away by the wind (wind erosion).

The opposite of dry dessert sand is soil saturated with water (right picture). In this case, the wetness from rain is accumulated in the soil. The surplus water pushes the soil grains apart and acts as a lubricant. As a result, the soil becomes unstable. This is the best condition for a mudslide.

Mudslides - Danger for Whole Villages

Intensive and continuous precipitation or a sudden thaw is able to loosen soil on a slope. In the worst case, it is able to set of a landslide and cause a catastrophe. In all these cases, water is the main factor.

Reasons for Landslides or Mudslides:

• Natural causes: earthquakes or eruptions of volcanoes.
• Constructions on hills: streets, houses....
• Alpinism: new ski resorts, hotels, hiking paths....
• Lack of undergrowth or protective forests due to insufficient reforestation, forest fires, forest dieback....

Preventive Measures:

• Reforestation,...
• Drainage
• Retaining walls,...

andslides always become tragic as soon as people are affected. Because of the growing population density in many countries, more and more settlements are spreading out into mountainous regions. This tremendously increases the risk of landslides in inhabited areas. The results are often devastating.