News: RP among most at risk from climate change

Source: Business Mirror (http://businessmirror.com.ph/home/top-news/7167-rp-among-most-at-risk-from-climate-change.html)

Written by Imelda V. Abaño / Correspondent
Sunday, 08 March 2009 22:05

THE picture of how global warming affects our country has become increasingly clear. In the new climate- change vulnerability map released on Friday by the International Development Research Centre’s Economy and Environment Program for Southeast Asia (EEPSEA), the Philippines was pinpointed as one of the areas most vulnerable to climate change in Southeast Asia.

The study revealed that the Philippines, unlike other countries in Southeast Asia, is not only exposed to tropical cyclones, especially in the northern and eastern parts of the country, but also to many other climate-related hazards—especially floods such as in Central Luzon and Southern Mindanao, landslides due to the terrain of the country, and drought.

Of the 530 cities and provinces assessed, Metro Manila was ranked seventh. Other climate hotspots identified in the Philippines which are susceptible to multiple climate hazards are Northern Samar, Benguet, Masbate, Batanes, Zamboanga del Norte, Ilocos Sur, Western Samar, Albay, Lanao del Norte, Misamis Occidental, Rizal, Batangas and Mountain Province.

“Climate change is the most significant challenge facing public policy-makers today,” said Dr. Herminia Francisco, director of EEPSEA. “The map highlights areas in the region that have recently experienced climate-related risks such as tropical cyclones, floods, landslides, droughts and sea-level rise. The map could be useful for climate-change policy.”

Jakarta in Indonesia came out as the most vulnerable region in Southeast Asia. Other countries identified are Vietnam, Cambodia, Thailand, Laos and Indonesia.

“The challenge for us is on how policymakers find ways to boost the resilience of populations in these climate-change hotspots. By helping people to understand what climate change means and on how to adapt, we can avoid the worst effects by taking a swift action,” said Richard Fuchs, IDRC regional director for Southeast and East Asia.

Moment of truth for state officials

Former senator Leticia Ramos-Shahani, who was at the launching of the vulnerability map, said today’s leaders have “a moral responsibility to future generations to take meaningful action.”

“This is a moment of truth for us and for the government officials. Climate-change action is a local demand for our survival. We are good in planning and research, but when it comes to implementation we are very weak,” Shahani lamented.

Shahani said the bigger problem is likely to be the decreasing capacity of vulnerable people to cope with disasters, coupled with the inaction of their governments.

“Climate change is a test for all of us. It’s not the elite but it’s the poor people who will be affected. Let us avoid internationalizing this issue too much, we have to be patriotic and local actions are urgently needed.”

Sen. Loren Legarda said in her speech that policymakers should devise ways to prepare vulnerable people for the impact of climate change by mainstreaming the issue in various phases of policy formulation, development plans, poverty- reduction strategies and other development tools and techniques by all state agencies and instrumentalities.

Legarda, who batted for the creation of the Climate Change Commission, said this body will help the country focus on reversing climate change and undertake climate-change adaptation and mitigating work.

“Looking at the map with the Philippines in a red alert color, it is sad and difficult because it means there’s so much work to be done. With the creation of the climate-change commission, we can expect leadership from the government to tackle climate change and reduce disaster,” Legarda said.

Energy Secretary Angelo Reyes emphasized the importance of preparedness in the face of extreme weather changes. He said mainstreaming climate change mitigation and adaptation is the government’s priority.

Roadside Landslide Prevention and Mitigation

Generally, the management of roadside landslide hazards takes place through reactive interventions (road clearance and repair) rather than proactive interventions (slope improvement and pre-emptive measures, such as retaining walls and bio-engineering applications).

Roadside landslide prevention and mitigation measures can be grouped into three: drainage measures, structural support measures, and soil bio-engineering measures.

Drainage Measures

Restoring natural drainage patterns is essential for the long-term effectiveness of landslide rehabilitation. Restoring drainage is recommended when landslides leave a steep headscarp at roads, cut across mid-slope roads, deposit debris onto a road, interrupt drainage patterns, or deposit debris in a gully or creek. Road drainage should be routed away from landslide tracks unless the landslide travels down a natural gully. Landslide debris should also be removed from road drainage structures. Lastly, too much water should not be diverted to a single culvert.

Structural Support Measures

Various types of walls such as gabion, stone masonry, composite masonry, etc. have been used to mitigate slope failures. Support structures such as rock bolts, earth anchors, anchored walls, etc. are also used. Usually, deep-seated landslides are treated with complex civil engineering structures, including large supporting walls, extensive drainage measures and technologies for anchoring unstable slopes to more solid ground.

Soil Bio-engineering Measures

Soil bio-engineering is the use of vegetation to reduce instability and erosion on slopes. It is relatively low-cost, uses local materials and skill, and provides livelihood benefits through economically useful products. The plants used can later become sources of firewood, grass, fodder, and maybe income.

Structural support measures can be applied in combination with drainage measures and soil bio-engineering measures. The improvements in the national highways of Nepal are a result of soil bio-engineering technology, which along with conventional civil engineering, has helped combat landslides. While standard civil engineering measures are usually required for the bigger failures, the more prevalent smaller problems can mostly be resolved using bio-engineering measures.

As human population grows and spreads, more road networks are produced. Consequently, the risk from roadside landslides increases. Roadside landslides are a threat to life and properties. However, numerous studies have shown that preventive and mitigation measures can be taken to minimize or eradicate the hazards and risks from roadside landslides.

Effects of Roadside Landslides

Damages that occur during and after a major disaster can be categorized as Direct Damages, Indirect Losses, and Secondary Effects.

Direct Damages are damages incurred during a disaster, like the total or partial destruction of buildings, transportation facilities, dams, machinery and equipment, farms, etc. Thus direct damage is the physical, material destruction that occurs as a result of a disaster.

The expenditure on emergency roadside landslide repairs in Laos ranged between USD 3 and 5 million per year. This is equivalent to an average landslide expenditure of between USD 1,000 and 1,500 per kilometer of road per year.

In northern Thailand, many houses were destroyed by flash floods and landslides and the accompanying debris flow.

Landslides also have direct environmental costs. Environmental damage due to landslides in Laos included: loss of trees of commercial value, either for timber or other products; permanent loss of topsoil and nutrients; increased sediment in water-courses, affecting water supplies and fisheries downstream; changes to riverbeds, leading to altered flood patterns; reduction of the water storage capacity of reservoirs, etc.

Indirect Losses occur immediately after a disaster due to interruptions in normal business and may last from several days to several years. The most common example is of indirect losses due to roadside landslides is traffic suspension. The majority of landslides resulted in temporary partial or complete obstruction of short segments of road. These gave rise to several hours of delay to traffic. The economic losses associated with road closures are therefore predominantly related to the cost of lost time.

The effects of a major disaster on a country’s overall economy constitute Secondary Effects. These include changes in the gross domestic product, the trade balance and the balance of payments, the amount of debt and monetary reserves, the robustness of public finance, gross capital formation, the inflation rate, the unemployment rate, and changes in the level of household income.

In short, the total cost of landslides should include the costs of physical damages, costs of economic disruption brought about by temporary road closures, and any environmental, social, and economic costs brought about by landslides.

Causes of Roadside Landslides

Landslides are the result of the interplay of two types of factors: predisposing factors (slope angle, soil type, vegetation cover, etc.) which put slopes in a range of situations ranging from completely stable to marginally stable; and triggering factors (rainfall, earthquake, etc.) that are responsible for the onset of the slope failure. Both types of factors determine the probability of occurrence of a landslide.

More than 90% of roadside landslide disasters in Japan were caused by heavy rain and only two percent by earthquake. Japan is exposed to heavy rainfall in the rainy season from June to July and in the typhoon season from September to October. Japan is prone to earthquakes as it is located on active tectonic plates.

Most of the landslides recorded in Laos were caused by high wet season groundwater and perched water levels in soils and weathered rock masses exposed to steep roadside cuts. Slope failures were often observed to originate from the upper portions of cut slopes where weaker material predominates in the weathering profile.

The intensive unscientific cutting of hills in India for new roads and for widening existing roads using heavy machinery had added to geological disturbances, resulting in the greater instability of hills and more slope failures. Every year the triggering of landslides occurs frequently in different locations, as a result of monsoon rains. Quarrying and the careless disposal of surplus materials were other sources of roadside landslides.

The main causes of landslides in Nepal were steep slopes, combined with loose material and excessive rainfall during monsoons. Activities such as severe cutting into hillsides, disturbing natural drainage systems, and inappropriate land use contributed to landslide risk.

Inappropriate land use in Thailand increased the risk of landslide. Farmers practiced slash and burn methods for farming on slopes without proper understanding of slope degradation and the potential for slope destabilization. In addition, slopes had been covered with inappropriate types of vegetation such as banana, bamboo, etc. The shallow root systems of these plants do not contribute much to soil stability.

In the Philippines, a study of the Baguio area determined that it is subject to many factors favoring the occurrence of landslides: the mostly mountainous terrain; a humid climate with frequently occurring typhoons and associated heavy rainfall; earthquakes; deforestation caused by logging, mining, industrial development, agriculture; etc.

In general, roadside landslides are more common in places where there is sloping terrain with unstable conditions. Landslides may cause a large number of deaths if there are houses or settlements in steep terrain and the population density is relatively high.

Incidence of Roadside Landslides

Roadside landslides are common worldwide. In Japan, 1,310 landslides along national highways 20,000 kilometers in length were reported from April 1990 to December 2004. Surface failure was the most abundant category and constituted 81% of all landslide disasters. The disasters had caused damage to the highways and temporarily suspended road traffic.

Landslides were also very frequent along highways in Hong Kong and large expenditures were incurred on the investigation, design, and implementation of mitigation and preventive measures to reduce loss of lives and damage to properties. Landslides in the mountainous terrain of Hong Kong often occurred during or after heavy rainfall.

In the predominantly mountainous Laos, road networks were also impacted by landslides. These landslides occurred most frequently as shallow slope failures in roadside cuttings. The majority of landslides resulted in partial or complete obstruction of short road segments. These gave rise to several hours of delay to traffic and required expenditures for debris clearance and road repairs. 70% of recorded roadside slope failures had taken place above the road.

Many roadside slopes in Himachal Pradesh, India also suffered from a range of instability and erosion problems. The widening of roads involved massive hill cutting, resulting in yet more unstable slopes.

Landslides were also recurrent in the mountainous Himalayan country of Nepal. Intense seasonal monsoon rains and weak rock and soil cover combined with improper land use practices make the landscapes in Nepal one the most unstable in the world.

Landslides and flash floods triggered by days of heavy rain affected five provinces in the northern part of Thailand in 2006, resulting to hundreds of people killed and thousands of other people stranded. Infrastructures such as bridges and roads were damaged.

With the rapidly increasing concentration of population and development of infrastructure, the loss of life and the damage to property caused by landslides in the Philippines in general and in Baguio in particular have grown significantly over the past decades.

However, despite the high incidence of roadside landslides, there are hardly any databases of roadside landslides available. Data on the extent and volume of landslides affecting roads are difficult to obtain, as there have been very few systematic records or study into the magnitude of the problem.

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.