Aim of this chapter is to show all the literature available related to landslides and it ‘s impact to socio environment. It would include what are natural catastrophes, precedence of happening of natural catastrophes, some thing about Sri Lanka and natural catastrophes in Sri Lanka ; something about landslides, landslides is the 1 of chief natural catastrophes for Hill state, grounds for landslides in Sri Lanka specially in Ratnapura territory, socio impact of natural landslides in Sri Lanka, extenuation of landslides in Sri Lanka.
A natural jeopardy is a menace of an event that will hold a negative consequence on people or the environment. In recent old ages, turning population and enlargement of colonies and life-lines over risky countries have mostly increased the impact of natural catastrophes both in industrialized and developing states. ( Guzzetti.F, et Al, Landslide hazard rating: a reappraisal of current techniques and their application in a multi-scale survey, Central Italy ) . Specially Asia and the Pacific is the universe ‘s most disaster-prone part, accounting for 91 per cent of deceases from natural catastrophes in the past century and 49 per cent of the ensuing economic harm ( ASIA – PACIFIC ENVIRONMENT OUTLOOK ) . It can be illustrated as follow. ( Figure 2.2.1 )
Figure 2.2.1: Impacts of natural catastrophes in the period 1900-2005
Beginning: EM – DAT, the OFDA/CRED International Disaster Database, Univercity Catholique de Louvain, Brussels, Belgium.
Each twelvemonth for the past 15 old ages, an norm of 41,000 people have died in the part from natural catastrophes, which yearly inflicted $ 29 billion worth of harm. Of the universe ‘s 10 most terrible natural catastrophes in 2004, five occurred in the Asiatic and Pacific part, doing harm amounting to $ 55 billion, approximately 70 per cent of the entire harm, estimated at $ 80 billion. Statistical Yearbook for Asia and the Pacific in 2007 presented major natural catastrophe events in the Asia and Pacific part from1988 to 2007.
( Figure 2.2.2 )
Figure 2.2.2 – Major natural catastrophe events in the Asiatic and Pacific part, 1988- 2007
Beginning: ASIA – PACIFIC ENVIRONMENT OUTLOOK
At the meeting of Management of Landslide jeopardy, Japan Landslide Society ( JLS ) presented two grounds for that state of affairs occurred in the Asia-Pacific Region. This include states trouble to confront the high costs of commanding natural jeopardies through major technology plants, rational land-use planning and different portion of landscape had been subjected to broad scope of catastrophe from clip to clip through out the history. The drouths, landslides, cyclone, air current, storms, dirt eroding, Tsunami and coastal eroding are the common natural catastrophes while terrorist act, force, civil struggles, detonations, industrial accidents, epidemics, treasure excavation, sand excavation, fires & A ; deforestation are the adult male made catastrophe that affect the community of the Asia-Pacific.
Since 1990 the part has suffered 50 per cent of the universe ‘s major natural catastrophes when International Decade for Natural Disaster Reduction began. The entire figure of deceases due to natural catastrophes in the part has exceeded 200,000 and the estimated harm to belongings over this period has been estimated at US $ 100 billion ( ASIA – PACIFIC ENVIRONMENT OUTLOOK ) .
A inundation is an flood of an sweep of H2O that submerges land, a flood. Floods are the most common climate-related catastrophe in the part and include seasonal inundations, flash inundations, urban inundations due to inadequate drainage installations and inundations associated with tidal events induced by typhoons in coastal countries. In Bangladesh, one of the most flood-prone states in the part, every bit many as 80 million people are vulnerable to deluging each twelvemonth ( ESCAP, 1995a ) . In India, where a sum of 40 million hectares is at hazard from deluging each twelvemonth, the mean one-year direct harm has been estimated at US $ 240 million, although this figure can increase to over US $ 1.5 billion with terrible inundation events.A ( ASIA – PACIFIC ENVIRONMENT OUTLOOK ) .
Implosion therapy is the most common natural jeopardy in Sri Lanka besides. Heavy monsoon rain has affected the South and South West of Sri Lanka, taking to the most serious implosion therapy and landslides in over 50 old ages. Six territories are affected by the inundations. This includes Ratnapura, Galle, Kalutara, Matara, Nuwara Eliya, and Hambantota disricts. Recent records indicate that Sri Lanka experiences big graduated table implosion therapy every 2 to 3 old ages on norm about 200,000 people are affected every twelvemonth. The Government of Sri Lanka Disaster Operations Center has provided the following informations on the affected countries:
( Table 188.8.131.52 )
Table 01: implosion therapy countries
Houses partly damaged
Beginning: The Government of Sri Lanka Disaster Operations Center
There are 103 river basins in the island of which about 20 can be considered major basins of the five chief rivers, the Kelani, Kalu, Gin, Nilwala and Mahaweli, which experience one-year inundations.
Floods in Sri Lanka occur chiefly due to excessive rainfall during the monsoons, and they usually occur during the Southwest monsoon and during the inter-monsoonal rains, merely before and after the Northeast monsoon. Therefore, rivers located on the Western incline of the state go prone to implosion therapy. . ( Malalgoda M, et Al, ITDG – South Asia, 2002 )
An temblor is a sudden and sometimes ruinous motion of a portion of the Earth ‘s surface. Earthquakes result from the dynamic release of elastic strain energy that radiates seismal moving ridges. Earthquakes typically result from the motion of mistakes, two-dimensional zones of distortion within the Earth ‘s upper crust. ( Cecil H, et Al, Green Institute of Geophysics and Planetary Physics at Scripps Institution of Oceanography ) . Earthquakes are recorded with a seismometer, besides known as a seismograph. At the Earth ‘s surface, earthquakes manifest themselves by agitating and sometimes displacing the land. When a big temblor epicentre is located offshore, the ocean floor sometimes suffers sufficient supplanting to do a tsunami. The shaking in temblors can besides trip landslides and on occasion volcanic activity. ( Spence, William ; S. A. Sipkin, G. L. Choy ( 1989 ) . “ Measuring the Size of an Earthquake ” , United States Geological Survey, 2006 ) .
Earthquakes are ephemeral, menacing and the most feared natural jeopardies because of their sudden impact and desolation in a affair of few seconds bring downing huge losingss of life and belongings. Therefore since we are non in a place to foretell an temblor, we must at least attempt to happen out the scientific causes that can take to such ruinous temblors. If non catastrophe due to earthquakes affects all sections of the community including persons doing important economic & A ; societal impacts, terrible harm to life & A ; human agony, loss of belongings & A ; material wealth, environmental desolations, desolation of physical installations ( Banerjee R, et Al Geomatics in Earthquake Mitigation, ESHD/MWRG-RESA, Space Applications Centre ( ISRO ) , Ahmedabad ) .
Cyclones are immense go arounding storms caused by air currents blowing around a cardinal country of low atmospheric force per unit area. In the Northern hemisphere, cyclones are called hurricanes or typhoons and their air currents blow in an anti-clockwise circle. In the southern hemisphere, these tropical storms are known as cyclones, whose air currents blow in a clockwise circle. Cyclones develop over warm seas near the Equator. Air heated by the Sun rises really fleetly, which creates countries of really low force per unit area. As the warm air rises, it becomes loaded with wet which condenses into monolithic cumulonimbus. Cool air hastes in to make full the nothingness that is left, but because of the changeless turning of the Earth on its axis, the air is dead set inwards and so spirals upwards with great force. The twirling air currents rotate faster and faster, organizing a immense circle which can be up to 2,000 kilometers across. ( Natural Catastrophes by Cindy, Lisa and Stacey ) .
The Eastern Coast of Sri Lanka is prone to black cyclones. The cyclone season is from November to December. About 83 % of happenings in the yesteryear have been during this period. In the cases where cyclones have hit Sri Lanka the effects have been lay waste toing. The cyclone of 1964 hit the territories of Polonnaruwa, Anuradhapura, Mannar, Batticaloa and Amparai. This cyclone resulted in 75,000 people being affected and 280 deceases. The cyclone of 1978 affected about 1 million people and an estimated 100,000 people were made homeless. . ( Malalgoda M, et Al, ITDG – South Asia, 2002 )
Droughts are caused by deficiency of rain over a long period of clip. Most drouths tend to happen during summer, as the conditions is hot and H2O is rapidly evaporated. It has been observed that the impact of drouths differs widely between developed and developing states because of the influence of such factors as H2O supply and water-use efficiency. The bulk of the estimated 500 million rural hapless in the Asia-Pacific part are subsistence husbandmans busying chiefly rain-fed land ( ESCAP, 1995a ) . The drought-prone states in this part are Afghanistan, Iran, Myanmar, Pakistan, Nepal, India, Sri Lanka and parts of Bangladesh. The Philippines, Thailand, Australia and the Pacific islands of Fiji, Vanuatu and Samoa besides contain drought-prone countries. ( ASIA – PACIFIC ENVIRONMENT OUTLOOK )
Dry enchantments and drouths are a perennial characteristic of the natural clime of Sri Lanka.
In the utmost Northwest Mannar and Kalpitiya countries and in the utmost sou’-west Yala country the average one-year rainfall beads below 1000mm. Hambantota, Moneragala and Puttlam are the administrative territories where drouth is a regular phenomenon.
2.3 Natural catastrophes in Sri Lanka
2.3.1 About Sri Lanka
Sri Lanka is an island in the Indian Ocean, located in Southern Asia, sou’-east of India, in a strategic location near major Indian Ocean sea lanes. It has a entire country of 65,610 kmA? , with 64,740 kmA? of land and 870 kmA? of H2O. Its coastline is 1,340 kilometer long. Sri Lanka ‘s clime includes tropical monsoons: the nor’-east monsoon ( December to March ) , and the sou’-west monsoon ( June to October ) . Its terrain is largely low, level to turn overing field, with mountains in the south-central inside. The highest point is Pidurutalagala at 2,524.13 m. Natural resources include limestone, black lead, mineral littorals, treasures, phosphates, clay, hydropower.
Extensive geological fault and eroding over clip have produced a broad scope of topographic characteristics, doing Sri Lanka one of the most scenic topographic points in the universe. Three zones are distinguishable by lift: the Central Highlands, the fields, and the coastal belt.
Sri Lanka ‘s clime can be described as tropical, and rather warm. Its place between 5 and 10 north latitude endows the state with a warm clime, moderated by ocean air currents and considerable wet. The average temperature ranges from a depression of 16A°C in Nuwara Eliya in the Central Highlands ( where hoar may happen for several yearss in the winter ) to a high of 32A°C in Trincomalee on the nor’-east seashore ( where temperatures may make 38 A°C ) . As a whole the mean annual temperature for the state ranges from 28 to 30 A°C. Day and dark temperatures may change by 4 to 7. January is the coolest month, doing people, particularly those in the Highlandss, to have on coats and jumpers. May, the hottest period, precedes the summer monsoon rains.
The rainfall form is influenced by the monsoon air currents of the Indian Ocean and Bay of Bengal and is marked by four seasons. The first is from mid-May to October, when air currents originate in the sou’-west, conveying wet from the Indian Ocean. When these air currents encounter the inclines of the Central Highlands, they unload heavy rains on the mountain inclines and the southwesterly sector of the island. Some of the windward slopes receive up to 2500 millimeter of rain per month, but the leeward inclines in the E and nor’-east receive small rain. The 2nd season occurs in October and November, inter monsoonal months. During this season, periodic squalls occur and sometimes tropical cyclones conveying cloud-covered skies and rains to the sou’-west, nor’-east, and eastern parts of the island. During the 3rd season, December to March, monsoon air currents come from the nor’-east, conveying wet from the Bay of Bengal. The northeasterly inclines of the mountains may be inundated with up to 1250 millimeter of rain during these months. Another inter monsoonal period occurs from March until mid-May, with light, variable air currents and flushing thundershowers. ( Library of Congress Country Studies, which are United States authorities publications in the public sphere, Geography of Sri Lanka ) .
2.3.2 Natural catastrophes in Sri Lanka
As a consequences of geological factors, weather status, human activities recent records indicate that Sri Lanka is a catastrophe prone state since historical clip. Different portion of landscape had been subjected to broad scope of catastrophe from clip to clip through out the history. But non merely natural catastrophes had been caused to present Sri Lanka as a catastrophe prone state, mane made catastrophes besides subject to this state of affairs. While the drouths, Landslides, Cyclone, Wind, Storms, Soil eroding, Tsunami and costal eroding are the common natural catastrophes ; terrorist act, force, civil struggles, detonations, industrial accidents, epidemics, treasure excavation, sand excavation, fires & A ; deforestation are the adult male made catastrophes that affect the community of the state. ( Jayaweera S, National Building Research Organization ) .
Those natural catastrophes had been affected all sections of Sri Lankan community including persons doing important economic and societal impacts, sever harm to life and human agony, loss of belongings and stuff wealth, environmental desolation of physical installations such as H2O supply, power coevals and distribution, telecommunication, arterial roads associating the affected countries to other portion of the state, township, wellness and instruction installations. ( Natural Disaster Risk Management Programme. Community Based Disaster Reduction and Recovery. Through Engagement of Communities and Local Self Governments ) .
Harmonizing to the alleviation distribution to the victims during past two decennaries, the most annihilating natural jeopardy has been landslides and inundations in footings of deceases and cost. Catastrophe due to landslides affects all sections of the community including persons doing important economic & A ; societal impacts. During the past few old ages landslide incidents seem to be increasing in figure and badness casing exposure of communities. ( Jayaweera S, National Building Research Organizatio )
2.4.1 Something about Landslide
A landslide is the down incline motion of deposit and stone. The word ‘landslide ‘ besides refers to the landforms that result from this action. Landslides are reflecting the many diverse landscapes ( Evans, S.G, Landslides ; in A Synthesis of Geological Hazards in Canada, G.R. Brooks ; Geological Survey of Canada, Bulletin, 2001 )
Landslides and mass motions are common phenomena in the universe, from the recent yesteryear. Especially landslides spread from the Central hills to adjacent territories preponderantly. This can be occurred in different sizes and it can be range signifier a individual bowlder that fell off a drop to a big country embracing 10s of square kilometres and 1000000s of three-dimensional metres of dust. And the velocity of motion can run from highly slow to highly rapid. The slowest motion, ‘creep ‘ , is on the order of a few centimetres to a few 10s of centimetres per twelvemonth. The fastest type of landslide, the stone avalanche, may make speeds of up to 100 metres per second ( 360 kilometres per hr ) , which exceeds the velocity of a race auto. ( Herath H.M.D.R, Department of SociologyA University of Peradeniya ) A
Landslides move down incline under the influence of gravitation ; although, if the geological stuff is peculiarly weak or sensitive or is saturated with H2O, gravitation is less of import. How the incline will neglect and how the stuff will travel is dependent on the specific geology and topography of the part. Some landslides move merely a short distance, coming to a halt near the base of the incline ; others can go several kilometres from the beginning. Some landslides will trip consecutive failures retrogress the caput scarp back into the incline. ( Evans, S.G. ( 2001 ) , G.R. Brooks ; Geological Survey of Canada, Bulletin ) .
Centers for Disease Control and Prevention ( CDC ) Atlanta, presented a specific countries which are more likely to see landslides. They are:
Areas where wildfires or human alteration of the land have destroyed flora ;
Areas where landslides have occurred before ;
Steep inclines and countries at the underside of inclines or canons ;
Slopes that have been altered for building of edifices and roads ;
Channelss along a watercourse or river ;
Areas where surface overflow is directed.
2.4.2 Types of landslides
Figure 184.108.40.206: Rock Slide
Diagram by J. Appleby, R. Kilbourne, and T. Spittler after Varnes, 1978
A landslide affecting bedrock in which the stone that moves remains mostly integral for at least a part of the motion. Rock slides can run in size from little and thin to really big and thick, and are capable to a broad scope of triping mechanisms. Rock slides normally occur on comparatively steep inclines in competent stones. Slope gradients are normally from 35 % to every bit steep as 70 % .
Figure 220.127.116.11: Earth Flow
Diagram by J. Appleby, R. Kilbourne, and T. Spittler after Varnes, 1978
Earth flows normally occur on reasonably steep inclines. Slope gradients are normally from 10 % to every bit steep as 30 % , although steeper inclines may be found in caput scarp and toe countries. Earth flows typically are initiated by periods of drawn-out rainfall and sometimes do n’t originate until good after a storm or the rainy season has passed. They are characteristically slow moving, in the millimetres or centimetres per twenty-four hours scope, and may go on to travel for a period of yearss to hebdomads after originating.
Figure 18.104.22.168: DEBRIS SLIDE
Beginning: Diagram by J.Appleby, R. Kilbourne, and T.Spittler after Varnes, 1978
Debris slides typically travel ab initio as shallow integral slabs of dirt and flora, but break up after a short distance into falls and flows. Motion of the slide mass as a shallow slab leads to a smooth, steep, normally curved cicatrix. The dust is deposited at the base as a loose hummocky mass, although the sedimentation may be quickly removed by eroding. Debris slides normally occur on really steep inclines, every bit steep as 60 % to 70 % , normally in an country where the base of a incline is undercut by eroding.
Figure 22.214.171.124: Debris Flow
Diagram by J.Appleby, R. Kilbourne, and T.Spittler after Varnes, 1978
Debris flows are most frequently triggered by intense rainfall following a period of less intense precipitation, or by rapid snow thaw. High pore H2O force per unit areas cause the dirt and weathered stone to quickly lose strength and flux down incline. Debris flows can travel really quickly, at rates runing from metres per hr to metres per second and travel comparatively long distances, doing them a important menace to life and belongings. Debris flows normally begin as a slide of a shallow mass of dirt and weathered stone. Their most typical landform is the cicatrix left by the original shallow slide. The way of the dust flow may be marked by a little drainage that has been stripped of flora. The dust flow may non go forth any sedimentation if it flows straight into a larger brook and is instantly eroded off. Many debris flow sedimentations are passing, but in some instances successive dust flows may lodge stuff in the same country thereby organizing a dust fan, which resembles a little, steep alluvial fan.
Figure 126.96.36.199: ROCK FALL
Diagram by J.Appleby, R. Kilbourne, and T.Spittler after Varnes, 1978
Rock falls occur on steep inclines of difficult, fractured stone. The cicatrix left by a stone autumn on the incline may be no more evident than an country of stone that is less weather-beaten than the environing stones. Rock autumn sedimentations are loose hemorrhoids of rubble that may be easy removed by eroding. Because neither the cicatrix nor the sedimentation are typical, and because the most often happening stone falls are typically little, single stone falls are normally non shown on regional-scale ( 1:24,000 and smaller ) landslide maps. Though infrequent, moderate- to large-volume stone falls can be highly unsafe and sometimes fatal. Large slabs of stone impacting a difficult shelf after a long bead can quickly interrupt apart, taking to air entrainment and long tally outs, induced air blasts, airborne missiles ( wing stone ) and terrible dust clouds.
( Varnes, D.J. , 1978, Slope motion types and procedures. In, Particular Report, R.L. Schuster and R.J. Krizek, National Research Council, Washington )
2.5 Landslides is one of the chief natural catastrophes in hill state
While deluging is most important for lowland, Landslides are the serious geologic jeopardy common to hill state. Recent rainfall in several parts of the state caused mayhem by manner of landslides in the hill state and inundations in low lands including Colombo City. Present landslide denseness in the cardinal Highlandss and the wet zone of Sri Lanka is estimated to be in the order of 1-2 landslides per sq. kilometer and about 20 % of the entire land country of the state, which supports about 30 % of the entire population, is capable to landslides.
Landslide prone countries are located in 7 territories in and next to the cardinal Highlandss, and 7-9 territories located in the moisture zone are prone to landslides. Namely Nuwara Eliya, Badulla, Kegalle, Kalutara, Kandy, Matale and late Matara, Galle and Hambantota are prone to landslides while Ratnapura territory is taking of import topographic point. ( Malalgoda M, et Al, ITDG – South Asia, 2002 )
Poorna S. Yahampath, proficient officer of catastrophe readiness illustrated that Most of countries in Ratnapura territory are affected by landslide ( Figure 08 )
Map 2.5.1: Catastrophe prone territory
Beginning: compiled by the writer
Beginning: Poorna S. Yahampath ; Technical Advisor – Catastrophe Preparedness ( 2008 )
Because of above state of affairs in Ratnapura territory National Building Research Organization ( NBRO ) have choose Ratnapura for launch presentation undertaking ( landslides, frequent implosion therapy, eroding, pollution and taint of H2O resources, land remission etc.
2.6 Landslides in Ratnapura territory
Landslides occurred in many countries such as Ratnapura, Pelmadulla, Kalawana, Nivithigala and Kahawatta in Ratnapura territory. Twenty Grama Sewa Niladhari ( GSN ) Divisions were affected due to landslides. Harmonizing to probes carried out by NBRO there are 135 bad countries, 69 medium hazard countries and 67 low hazard countries in the whole of Ratnapura District. The jeopardy analysis carried out by the Ratnapura Disaster Management Steering Committee ( RDMSC ) in 1999 under the SLUMDMP identified the undermentioned jeopardies in the order of frequence of happening shown as per centum on the graph below. This information reveals that Ratnapura is vulnerable to multiple jeopardies. Harmonizing to that probe catastrophes due to landslide took a second topographic point.
Figure 2.6.1: multiple jeopardies in Ratnapura District
Beginning: Asiatic Disaster readiness centre
Table: 2.6.1 Landslides in Ratnapura territory
Beginning: Poorna S Yahampath, UK – South Asia scientist and Practitioners ( 2008 )
The landslides in Ratnapura District, Sri Lanka in May 2003 once more showed the high exposure of the community life in the country. On 17th May 2003, Ratnapura had highly heavy and unusual rainfall of 347.2 millimeters within 24 hours. Many landslide happenings have been observed within the Ratnapura territory environing the municipality country. Sliding of Lawulu Kella, Panapola Kanda, Muwagama Kanda were take precedence. This was recorded as the most terrible event. These three landslides were the most vulnerable that have of all time recorded since historically. ( Asiatic catastrophe readiness centre: instance survey on extenuating catastrophes in Asia and the Pacific )
2.7 Reasons for landslides in Sri Lanka specially in Ratnapura territory
Landslides normally occur in connexion with other major natural catastrophes such as temblors, vents, wildfires, and inundations. Landslides occur due to natural phenomena and adult male made activities besides contributes to reactivate old landslide. Hilly country of Sri Lanka are affected or threatened by landslides when rains persist with increased strength. Observations on rainfall informations of land slide affected parts suggest that in the earlier times intensive precipitation of ( 200m – 300m ) in 24 hours triggered landslide. However, with increased human intercession the inclination for the happening of a landslide was high with a precipitation of 100 mm/ hour. ( Jayaweera S, National Building Research Organizatio )
Natural phenomena can be divided in to three classs. They are geological factors, morphological factors and physical factors. Weak stuffs, sensitive stuffs, weather-beaten stuffs, shorn stuffs, jointed or fissured stuffs, adversely oriented discontinuities, permeableness contrasts, stuff contrasts are can be identified as a geological factor. incline angle, upheaval, recoil, fluvial eroding, wave eroding, glacial eroding, eroding of sidelong borders, subterraneous eroding, incline burden, flora alteration are categorized as a Morphologic causes. Physical factors are the factors that intense rainfall, rapid snow thaw, drawn-out precipitation, rapid drawdown, temblor, volcanic eruption, dissolving, freeze-thaw, shrink-swell, ground H2O alterations. ( Malalgoda M, et Al, ITDG – South Asia, 2002 )
Man made factors besides straight capable to landslides. The ground for increasing adult male made factors is population growing in Sri Lanka. Harmonizing to Annual Report of Central Bank resent old ages ‘ population and denseness rate in Sri Lanka is higher than 2001. So this is a clear indicant of the heavy force per unit area, peculiarly on agricultural lands. Environment jobs will be created with population growing distribution and denseness. The human population destroys wildlife home grounds in many ways such as due to lodging, built roads uncluttering woods or any sort of development piece of lands on land. There is a close relation between demographic force per unit area in hilly countries turning environmental debasement and landslides. The haphazard development and inappropriate resources and land use, Civil buildings on hilly terrain without proper geotechnical probe non-provision of suited drainage systems or obstruction of drainage systems and /or natural watercourses, earthwork which alters the form of a incline are conducive factors to landslide.
2.8 Socio impact of natural landslides in Sri Lanka
Natural catastrophes have a profound impact on the quality of life through their devastation of nutrient harvests and farm animal, and forced disruption of families and communities. Their toll on lives and the instant poorness they cause are among their most annihilating impacts. The part histories for a bulk of the entire figure of deceases caused by natural catastrophes globally. The figure of natural catastrophes has been increasing around the universe, but the tendencies in lives lost and harm caused have changed in recent old ages due to effectual usage of engineering, communicating and transit systems. Over the past five decennaries, the mean figure of deceases caused yearly by natural catastrophes was ( Statistical Yearbook for Asia and the Pacific 2007 ) about 100,000 ; in contrast, the norm over the last 15 old ages has been about 41,000.
As low-income states of South Asiatic states consider as a more threaten counties by Natural Disasters. The sustained attempts for economic growing of those states are frequently interrupted by perennial natural catastrophes with considerable impact worsening poorness conditions in different parts of the part.
Since times of live history South Asiatic states have been confronting the onslaught of natural catastrophes such as inundations, cyclones, temblors, landslides, etc. The low-income states of South Asia i.e. Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan and Sri Lanka accommodate a big population of over a billion. The sustained attempts for economic growing of these states are frequently interrupted by perennial natural catastrophes with considerable impact worsening poorness conditions in different parts of the part. Among above that Asiatic Countries Sri Lanka see as a one of chief affected state by Natural catastrophes. Flood and landslides are most common natural catastrophe which has occurred in each and every twelvemonth since 1981 to 2007 along with other natural catastrophes in Sri Lanka. Brammer, Bangladesh Country Study, 1991 ) .
Landslides and mass motions are common phenomena in Sri Lanka, from the recent yesteryear. The effects of landslides cause in footings of casualties and extended harm to the roads, Bridgess, dikes, edifices, woods, paddy Fieldss farm secret plans and animate beings. Once these events occurred in uninhabited country is merely of scientific involvement and non considered as a catastrophe. When the such events kill and injure people, wounded communities, destroy places, make emphasis, do economic adversities, make exposure of people such events cause disaster.A Landslides risky operate on changing graduated tables. In order to diminishing badness, the undermentioned menaces can be recognized.A
Hazard to peopleA A 2. Hazards to goods
3. Hazards to environment 4. Hazard to development A
Common impact associated with landslides is danger to life, belongings and substructure. Refugee loses their relations and neighbours, belongings, houses and lands, employment chances, income, instruction and so on. The impermanent adjustment countries have to portion common resources and unfamiliar countries doing terrible societal jobs such as restrictions of basic demands, congestion, noise and harm to wellness, privateness struggle and finally the decrease of quality of life. Finally any type of natural catastrophes caused to Psychological emphasis of people, Social insecurity of adult females, Robberies and robbery.
Landslide and inundations are attendant events of intensive rain. The blocking of drainage canals due to landslides reduces the capacity of the drainage, watercourse and rivers result in unexpected implosion therapy.
Majority of the community of the hill incline is chief income beginning is agricultural merchandises. Large scale mass motions take topographic point due to long term dirt eroding ensuing in full cultivation enroot gets distracted. In add-on harm to agribusiness cause sever societal job.
Landslide cause sudden and big graduated table dirt eroding, block route ways, watercourses and other natural drainage system
Finally this straight capable to economic devastation and poorness in Sri Lanka. It ‘s affect to development of Sri Lanka.
( Herath H.M.D.R, Department of SociologyA University of Peradeniya ) .
2.9 Extenuation of landslides in Sri Lanka
Landslide extenuation plants are conducted in order to halt or cut down the landslide motion so that the resulting amendss can be minimized. The landslide extenuation plants are loosely classified into two classs: 1 ) control works ; and 2 ) restraint plants.
2.9.1 Landslide Control Works
Surface Drainage Control Works: The surface drainage control plants are implemented to command the motion of landslides accompanied by infiltration of rain H2O and spring flows. The surface drainage control works include two major plants: drainage aggregation plants and drainage channel works. The drainage aggregation plants are designed to roll up surface flow by put ining corrugated half pipes or lined U-ditches along the inclines, and so connected to the drainage channel. The drainage channel plants are
designed to take the gathered H2O out of the landslide zone every bit rapidly as possible, and are constructed from the same stuffs as the drainage aggregation works.
Subsurface drainage Control Works: The intent of the subsurface drainage control works is to take the land H2O within the landslide mass and to forestall the influx of land H2O into the landslide mass from outside beginnings. The subsurface drainage control works include shallow and deep subsurface drainage control works.
Soil Removal Works: This is one of the methods where the most dependable consequences can be expected, and by and large applies to little to medium sized landslides. Except for particular instances, the dirt remotion is focused on the caput part the slide.
Buttress Fill Works: The buttress fill is placed at the lower parts of the landslide in order to counterpoise the landslide mass. It is most effectual if the dirts generated by the dirt remotion plants are used.
River Structures: Degradation and channel bank eroding cut down Earth stableness and frequently tends to bring on slide activity. In such instances, cheque dikes, groundsill and bank protection can be constructed to forestall farther eroding.
2.9.2 Landslide Restraint Works
Pile Works: The heap works consist of driving hemorrhoids as keys to bind together the traveling landslide and the stable land to keep the motion. Generally, a midst walled steel pipe is used as the heap, and is so filled with concrete
Large Diameter Cast-in-Place Pile Works: The big diameter cast-in-place works map similar to those of the heap plants and are designed to bind the traveling landslide and the stable land together. However it involves much larger diameters. The building is similar to the drainage good, and by and large consists of heap of 1.5 to 6.5m in diameter and filed with strengthened concrete. Compared to the hemorrhoids, the big diameter cast-in-place type are much more immune to flexing emphasiss
Anchor Works: The ground tackle works use the tensile force of anchor organic structures embedded through the slide mass and into stable Earth, and are connected to thrust blocks located on the land surface. The push blocks are anchored with a sinew that counteracts the drive forces of the landslide to keep the slide motion. The advantage is that big restraint forces can be obtained from a comparatively little cross sectional sinew
Retaining Walls: Retaining walls are constructed to forestall smaller sized and secondary landslides that frequently occur along the toe part of the larger landslides. Because of the large-scale earth-movement and legion springs that are expected in landslide terrain, cot walls are common alternatively of conventional strengthened concrete retaining walls
( Cruden D.M. , VARNES D. J. ( 1996 ) – Landslide types and procedures. In: Turner A.K. ; Shuster R.L. ( explosive detection systems ) Landslides: Probe and Mitigation ) .