Introduction to Roadside Landslides

Landslides are a major concern in many countries around the world. Landslides cause enormous socioeconomic losses. They are sudden onset geological hazards. This means they offer short or no warning and they cause immediate damage. Landslides can be triggered by various stimuli, like intense rainfall, earthquakes, water-level changes, storm sea waves, etc.

Every year, landslides cause numerous deaths and injuries. They destroy houses, buildings, roads, bridges, and other infrastructures. To make matters worse, climate change has raised the intensity of rainfall in some parts of the country, consequently raising the frequency of rain-induced landslides. The high population growth rate and the increase in the number of houses in potentially hazardous spots, like roadsides in steep areas in the provinces, are also intensifying the impact of landslides.

Many roadside areas are susceptible to landslides whenever there is continuous heavy downpour. Some landslides make it to the news but most do not, especially if there are no casualties. When landslides occur in main thoroughfares, like along national highways, the transportation of people and of goods become paralyzed.

Areas become landslide-prone due to side cuts made on mountainsides to pave the way for the expansion and concreting of highways. Usually, only coconuts and bananas are planted on the road sides and these crops are not enough to prevent soil erosion during heavy rains. In general, people blame forest denudation for the increasing number of landslides experienced in the country.

While large-scale roadside landslides are not common, the cumulative costs to the government of the frequent small-size to medium-size roadside landslides may become considerable over time if these are not addressed early.