Group Members: Fatou Diagne Derek Dickinson Anthony Allard Demond Mayfield

It was suggested that there should be more of an emphasis on disaster prevention, a new concept in a region hampered by a strong belief in fate. But experts say too little progress is being made in institutionalizing preventive planning. Though the earthquake and after shocks that caused he landslides in El Salvador could not have been predicted, it is widely known that Central America covers the meeting points of six tectonic plates, it counts more than two dozen active volcanoes, and its shores are vulnerable to tropical storms half the year. The failure of the slope in Las Colinas has been found to be related to high water content of the lower part of the slope, which has been attributed to natural drainage blockage by a retaining wall observed on the bottom of the slope. In this instance a preventative measure may have aided in the cause of the landslide. Short-term measures: (1) Crack maps (2) Stopping water to permeate soils through cracks (3) Continuous monitoring of crack openings Full measures: (1) Removing remaining soil masses (2) Preventive and/or drainage works (3) Anchoring (4) Reinforcing with concrete crib arrangement (5) Piles As for extremely large slope failures, however, it is very difficult to stop them. It is therefore strongly recommended to develop and enforce land-use building ordinances that regulate constructions in areas susceptible to landslides and debris flows. For this, it is necessary to study basic features of such volcanic products as pumice and tuff. This information will allow us not only to simulate the possible travel distance and the velocity of a soil mass, but also to set up an alarm system. “Training Trainers Program� will be also effective. If local people and/or officers are familiar with the land around them, they will be able to catch an early signs of a landslide. The ring shear test of the water-saturated pumice soil in this paper clearly shows that the apparent friction angle can drop down even to a few degrees after slipping some distance. This indicates that the soil deposit is particularly susceptible to landslides during intense rainfall. Any changes in patterns of water drainage should be watched; the early signs include steadily developing cracks, some fragments of rocks coming off, or progressively tilting trees – all necessary pieces of information for the local people and authorities to be prepared for a possible evacuation. El Salvador is no stranger to natural disasters however some observers have claimed that the government response to the disaster in El Salvador has been poorly organized and in particular that the lessons from Hurricane Mitch (1999) were clearly not learnt. For example, most aid arriving at Comalapa International Airport, located on the coastal plain, was transported almost 30 km to the Feria Internacional in San Salvador for centralized logging and then distributed to affected areas, several of which were within 1 hour’s drive of the airport. In badly affected rural areas it was generally indicated that government assistance, in the first few weeks of the crisis, was not getting through to many of the earthquake victims. The main response to the emergency seems to have been provided by the affected people themselves. Although important contributions by NGOs and others, including contingents of the Venezuelan Armed Forces and, changing their historical role, the Salvadorian Armed Forces as well, should not be overlooked. Mexico was one of the first countries to respond to El Salvador's needs, sending tons of food, blankets, and medicine, as well as 150 soldiers and dogs specially trained in disaster relief. Accompanying the soldiers is the director of Mexico's National Disaster Prevention Center, Oscar Navarro, who recently helped direct disaster-prevention efforts in response to the eruption of the Popocatepetl volcano outside Mexico City. More than 1,000 Red Cross staff and volunteers are working round the clock on search and rescue activities in several disaster sites throughout El Salvador. The Red Cross' had 120 ambulances operating through out El Salvador. The International Federation of Red Cross and Red Crescent Societies released 200,000 Swiss francs from its emergency fund and launched a preliminary appeal for 1.12 million Swiss francs to support initial needs. These were: the continuing emergency rescue effort, temporary shelter materials, food, water and sanitation and ongoing assessments. CARE begun the urgent task of distributing food, water, mattresses and shelter materials to thousands of earthquake survivors in El Salvador., CARE set a $2.5 million fundraising goal from private and governmental sources to support the emergency effort and longer-term recovery programs in El Salvador. The Government of El Salvador in light of the effects of the Los Colinas landslide had implored a better relief system that can get to areas affected by natural disasters faster and are more capable to assist in aiding affected persons.

Acknowledgements and References Special thanks to Ms. Lynn Highland, Director of the Landslide Division at the United States Geological Survey. JSCE, Las Colinas Landslide caused by the January 13th 2001 off the coast of El Salvador earthquake, 2002, Journal of Japan Association for Earthquake Engineering Vol. 2 No. 1 2002 The El Salvador earthquakes of January and February 2001: context, characteristics and implications for seismic risk J.J. Bommera,*, M.B. Benitob, M. Ciudad-Realc, A. Lemoined, M.A. Lo´pez-Menjı´vare, R. Madariagad, J. Mankelowf, P. Me´ndez de Hasbung, W. Murphyh, M. Nieto-Lovoe, C.E. Rodrı´guez-Pinedai, H. Rosaj

Soil Exploration Soil Exploration is an account of the methods used in the analysis of the landslide. The JSCE employed many tactics in draw conjectures about the landslide from visual observations to soil tests. Land Surveying Surveying of the Las Colinas sliding surface was assisted by Laser Ace 300, a laser based theodolite. Accompanying a portable computer, the device calculates the azimuth, dip angle, and horizontal distance to a point. According to the soil characteristics of the landslide, the slope was able to be divided into three zones: uppermost main scarp (Zone 1), steep slope in the middle (Zone 2), and gentle toe slope leading to the flushed residential area (Zone 3). Soil Profile Pictures taken by Jose Antonio Riva (Geotermica Salvadorena) on two separate dates conveyed a contrast to the JSCE team. Dark colored stripes indicated that exposed soils were drying and furthermore that the soil was moistened. The apparent crumbling of the soil simply by rubbing together with fingers further deduced that the soil was weakly cemented. Other observations that JSCE team made were the cracks and joints located where the soil was still intact. This led to deduce that further slides was not out of the question. Using the instrument of a GPS receiver, 43 points were marked along the perimeter of the scar. Over a distance of 22m, a total of 1.25m of openings resulted from 12 visible cracks. The edges of the cracks were lightly dusted with fine sand. This reiterated the team’s premise that the landslide caused some soils to liquefy through the underground water level. Zone 2 encompassed much of the mud-like soils and led to liquefaction ideas. Zone 3, the toe of the slope, housed much of the damage of the landslide. The JSCE team measured the splash of the mud on trees and houses to later deduce the time it took for the splash to occur using projectile equations. This highlights the intensity of the landslide and possibly the extent to which what could cause 500 deaths. In-situ tests Portable cone penetration tests were administered by the JSCE team to ascertain the strength of the soil. Conducted at three different points along the mountain, the parameter of depth was considered. Ns values, obtained from the tests, were evaluated to result in overall low values (values of zero were found at 1.2m and 2.5m). It was deduced that it was these low values that equated weak layers or soil related to fragmental volcanic products or pumice. Ring Shear Test Dynamic characteristics of soil can be observed through instrumentation of an undrained ring shear apparatus. The apparatus maintains shear/normal stresses along a sliding surface inside the box, while physical quantities of the soil sample are observed in real time. Visual observations of the soil not only showed moist to wet soil being present within the soil stratification, but that liquefaction may have played a factor in the landslide. Being that ring shear tests may determine liquefaction, two tests were conducted: each normally consolidated, under a stress state relating to a slope of 20° inclination, but varied by their degrees of saturation (Sr=100 Sr=81. The second test utilizing a saturation degree of 81determined that the soil in situ was not completely saturated.

Social Effects The landslide following the earthquake of January 13, 2001 caused the damage and destruction of many houses; making thousands of people homeless. The population of that area is mainly composed of coffee plantation workers that are forced to live in those susceptible areas. An overwhelming majority of the damaged houses were made of adobe and bahareque. The population of that area constructs their houses with adobe and bahareque because it is the cheapest material. Roofs of adobe houses may be of metal sheets and/or clay tiles supported by wood trusses or thatched roof supported on wood t imber purlins. Load transfer between the roof and walls, or between walls, is often not effective. This building system has high mass and stiffness but low strength. Bahareque consists of timber vertical elements and horizontal timber, cane or bamboo elements, infilled with mud and finished with plaster. The seismic resistance of bahareque depends primarily on the condition of the timber and cane elements, having low vulnerability when carefully maintained. Bahareque is a more expensive building system than adobe. Roofs are similar to those for adobe and show the problems. Mixto is composed of fired clay bricks with mortar and slender elements of concrete with thin steel reinforcement, or the same thickness as thewall,which are not properly reinforced concrete and are known as nervios (nerves or tendons). This system, in which the masonry walls provide the load bearing system, has relatively good seismic resistance but is considerablymore expensive than both adobe and bahareque. Lamina is the name given to buildings of timber or metal frames covered by thin metal sheets, usually founded on a 50 cm high blockwall. Lamina has good seismic resistance due to its low weight and mass. Wood frames covered by palm fronds have excellent seismic response characteristics but this building system is rapidly disappearing due to scarcity of materials. Most of the cultural heritage buildings that were in place since the colonization did nit survive the landslide. Economical Effects For years, the main cash flow has been the coffee exports. The landslides destroyed a significant part of that area seriously affecting the economy. Damage patterns clearly revealed the social vulnerability of the population of Santa Tecla. The major hospitals remained closed because of loss of functionality and damage of non- structural parts. This landslide that affected every aspect of that region specifically the coffee plantation and the roads handicapped the whole economy. Infrastuctural Effects The telecommunication was not seriously affected; within one day the service was fully restored. The electricity generation was not seriously affected but the large number of lines broken affected the generation system. There was no major disruption of the water treatment and wastewater treatment distribution system. One infrastructure seriously affected was the transport lines. The roads were blocked by rocks falling, the bridges failed and some of the ports were inaccessible.

PREVENTION & CORRECTIVE MEASURES Ecological organizations long had warned that construction and deforestation in the hills above Santa Tecla had endangered the community. Las Colinas lies at the foot of the Cordillera del Balsamo, a range of steep hills with loose soil. After a 1986 earthquake, engineers and builders prepared a booklet designating high-risk zones, including the Cordillera del Balsamo. Santa Tecla Mayor Oscar Ortiz tried to stop construction on the hillside after a former housing minister obtained a waiver to build luxury mansions there. The Supreme Court ruled in favor of the construction companies, therefore the buildings were constructed. However, not enough preventative measures were put in place. To prevent landslides, measures are roughly divided into prevention works and determent works. The purpose of prevention works are to stop or prevent landslide movement by changing natural conditions, such as topography, geology, and groundwater condition. On the other hand, the purpose of determent works is to deter part or all of landslide movement with structures.

REFLECTION Landslides are experienced in just about every country in the world. In the Caribbean the main causes of landslides are deforestation, farming, and construction of roads. In California most of the landslides are cause naturally because of the fault lines that run through the state. The movement of the plates causes vibrations and pressure, which cause the destabilization of slopes, causing landslides. However, common to both areas is the impact that excess rainfall has on the slopes. In the lower Caribbean countries such as Trinidad and Tobago the rainy season is coupled with ITCZ (Inter Tropical Convergence Zone) causing excessive rainfall during the later months of the year. Though the soil characteristics imply that the soil strength is high in the Caribbean, the consistent heavy rainfall causes occasional landslides. In California where the weather is usually dry the majority of the year, the soil is not capable of holding much water. Therefore in fall where the rainfall is higher the soil is unable to hold the water and quickly becomes saturated. In Senegal where the land is mostly flat excessive rainfall usually results in flooding in low-lying areas. In Trinidad and Tobago where the geotechnical engineering is rarely practiced and geoctechnical technology is not very widely used, the slopes are not necessarily cut in the best way and usually result in land slides. Mainly vibrations of vehicles traveling on the road and rainfall cause sliding. The preventative measures used are limited by the availability of technology resources and finances. Therefore the main forms of prevention used include small retaining walls at the base of slopes, fences and drains down the slopes. The slope and soil stability tests aren’t usually done before the slope is cut and as a result, sufficient preventative measures are not put in place. With this said, a culmination of efforts employ geotechnical engineers to ensure, or attempt to ensure, that catastrophic landslides do not occur. Education lies as the strongest arm to combat natural disasters. The innovation of landslide mitigation stems from fundamentals behind materials and their mechanics about the environment. Soil and fluid mechanics highlight the behavior of soils and fluid like soils (mudslides). Utilizing these theories with fundamentals obtained in Structures, engineers become equipped with tools to not only prevent natural disasters from occurring, but allowing a method of tackling the problems they encompass. Landslides however are very difficult to predict and because of this they usually cause catastrophic damage when they do occur. The damage seen is not only physical but also the scars left on those affected including the emotional, psychological, the mental and the spiritual. Those affected by such events have to bear the burden of putting together shattered lives of friends and family members alike. The affected must now start to look at rebuilding amidst the torture of deaths and displacement. The devastation can certainly be equated to that of the mass chaos of Hurricane Katrina with the major difference being the economic status of the persons affected in a place such as El Salvador. The relief that is seen in these countries is sometimes non-existent and the affected are usually left to their own devices to rebuild physically as well as mentally. In the analysis done on the cause and effects of landslide, there are many factors to consider and a closer look is always taken for the prediction and even the prevention of the slides. With the introduction of new technology in the study of earthquakes, geology and even soil mechanics headway is being made not to prevent but to make certain that if they do occur measures are in place to restrict the damage and also to have a mechanism in play for alerting the inhabitants close to the affected areas. It is still however pertinent that measures are taken to educate about these natural occurrences. The treatment of the land in terms of its uses and proximity of habitation should be closely considered. Government action is needed to secure the lives and well being of their constituents because these events lead to many economic downturns in what may already be considered an economically poor environment. And just as the events of hurricane Katrina the ones mostly affected are those with the littlest means and those who belong to your general working class. El Salvador is still trying to recover from the effects of a series of earthquakes, hurricanes, landslides, and floods. The economy is slowly growing and the preventative measures needed cannot be put in place simply because the funding is not there. The government cannot afford to spend money to prevent further catastrophes when the citizens still need aid from the effects of the previous disasters. Trinidad and Tobago have only recently begun to use larger retaining walls and newer geological technologies to prevent landslides. However, El Salvador does not have the income enjoyed by Trinidad and Tobago from oil and as the natural disaster destroy their means of income, agriculture, we are seeing the future for El Salvador disappear. Thankfully organizations such as CARE and the Red Cross have continued to be at the forefront in the rebuilding of El Salvador and lobbying for financial aid for countries like El Salvador so that the available technology can be acquired and used.