3.7.6 Landslides Seasonal Distribution
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Sri Lanka National Report on Disaster Risk, Poverty and Human Development Relationship 3.7.6 Landslides Seasonal Distribution 3.7.6.1 Distribution Seasonal distribution of landslides demonstrates a Annual Time Series Distribution clear link with the distribution of the rainfall as illustrated in Figure 61. The records of landslides are Landslides had been traditionally considered as a high in the months of May and June and once again minor type of disaster and not a common occurrence from November to January, showing a clear in Sri Lanka. Until the year 2002, the annual average relationship with two monsoon seasons in Sri Lanka. number of landslide records did not exceed 50 The second peak is higher than the first and (Figure 60). However, the data shows a sudden November has the highest recorded landslides, increase in the occurrence of landslides during the exceeding more than 275 incidents. period 2003 – 2008. Figure 60 : 400 Annual 350 Time Series Distribution of 300 Landslides nts 250 200 er of eve b 150 Num 100 50 0 1984 2000 1994 1988 1980 1986 2006 1992 1996 1990 2004 2002 1978 1974 1976 1982 1998 2008 source www.desinventar.lk Year Figure 61 : 300 Seasonal 250 Distributions of Landslides: 200 1974 - 2008 150 of events 100 Number 50 0 y y July May April June March August ebruar Januar October F November source December September www.desinventar.lk Month 91 Chapter 03 Disaster Event and Impact Profile Spatial Distribution With respect to spatial distribution (Map 37), most most landslide-prone districts. A similar pattern can landslides appear to occur only in the Southern, Uva be observed on the map for DS divisions where the and Central province within the districts of Badulla, higher incidence can be seen within the Uva Nuwara Eliya, Kegalle and Rathnapura, which are the Province. Map 37 : Spatial Distribution of Landslides: 1974 - 2008 source District DS Divisions www.desinventar.lk 92 Sri Lanka National Report on Disaster Risk, Poverty and Human Development Relationship 3.7.6.2Impacts As most landslides appear to have occured only People Affected (Annual Time Series and within the Southern, Uva and Central provinces, Spatial Distribution) people affected are generally confined to this area (see Map 38). The highest impact can be seen in the As the incidence of landslides is relatively low and districts of Badulla, Nuwara Eliya, Kandy and most of them are minor incidents, the overall number Rathnapura districts. A similar pattern can be seen of people affected is also quite low (Figure 62). on the map for DS divisions where the highest impact However, a significant number of people were can be observed in DS divisions in the Uva Province. affected by landslides in 1986, 1989, 2003 and 2007. Figure 62 : 45000 People 40000 Affected Due to 35000 Landslides 30000 – Annual Time affected 25000 Series people 20000 Distribution 15000 er of b m 10000 u N 5000 0 1982 1992 2002 1978 1988 1998 2008 1974 1976 1980 1984 1986 1990 1994 1996 2000 2004 2006 source www.desinventar.lk Year Map 38 : People Affected Due to Landslides – Spatial Distribution : 1974 - 2008 source District DS Divisions www.desinventar.lk 93 Chapter 03 Disaster Event and Impact Profile Loss of life (Annual Time Series and Spatial year 2003 coming next. Spatially too (Map 39), the Distribution) loss of life has shown a similar pattern as the number The occurrence of death is greater and more of people affected. The highest death toll was frequent than the number of people affected (Figure experienced in the districts of Nuwara Eliya, Kegalle, 63). It can be observed that in almost all locations in Badulla and Ratnapura. A similar pattern was also the countr y, where landslides have been observed in the case of deaths experienced in the DS experienced, there has been loss of life. The highest divisions. death toll due to landslides was experienced in 1989, Figure 63 : 300 Loss of Life 250 Due to Landslides 200 - Annual Time Series 150 Distribution 100 Number of deaths 50 0 1982 1992 2002 1978 1988 1998 2008 source 1974 1976 1980 1984 1986 1990 1994 1996 2000 2004 2006 www.desinventar.lk Year Map 39 : Loss of Life Due to Landslides - Spatial Distribution : 1974 - 2008 source District DS Divisions www.desinventar.lk 94 Sri Lanka National Report on Disaster Risk, Poverty and Human Development Relationship Destroyed and Damaged Houses (Annual Time 2007 (Figure 64). With respect to spatial patterns, Series and Spatial Distribution) destruction and damage to houses follows a similar During the period reviewed, the destroyed and pattern to that experienced by people affected and damaged houses have been quite low with the loss of life (Map 40). exception of 4 years, namely, 1986, 2003, 2006 and Figure 64 : 4000 No of Houses 3500 Destroyed oyed and Damaged 3000 Due to Landslides - 2500 Annual Time Series 2000 Distribution 1500 1000 500 Number of houses damaged and destr 0 1982 1992 2002 1978 1988 1998 2008 1974 1976 1980 1984 1986 1990 1994 1996 2000 2004 2006 source www.desinventar.lk Year Map 40 : No of Houses Destroyed and Damaged Due to Landslides – Spatial Distribution : 1974 - 2008 source District DS Divisions www.desinventar.lk 95 Chapter 03 Disaster Event and Impact Profile Losses to Agricultural Crops (Annual Time However, very high crop loss was experienced in Series and Spatial Distribution) 2007. This was probably due either to the high intensity of the landslides or the area of occurrence. The occurrence of damage to paddy and other crops Landslides occurring during the harvesting period by landslides is not very significant and evenly would cause severe crop loss. Spatially, most of the distributed chronologically (Figure 65). From 1974 to crop loss is centralized within the Southern, Western 1984, there were no recorded damages but 1985 to and Uva provinces, with most loss being experienced 1990 represent a cluster of years showing damage. in the districts of Kandy and Badulla (Map 41). A From 1991 to 2001 there were no records of similar pattern can be seen in the DS divisions as well. damages, except for a few instances in 1997. Figure 65 : 700 Agricultural 600 Loss Due to loss Landslides ( in 500 Hectares) – 400 gricultral Annual a 300 Time Series of Distribution es 200 ectar 100 H 0 1982 1992 2002 1978 1988 1998 2008 source 1974 1976 1980 1984 1986 1990 1994 1996 2000 2004 2006 www.desinventar.lk Year Map 41 : Agricultural Loss Due to Landslides ( in Hectares) – Spatial Distribution: 1974-2008 source District www.desinventar.lk DS Divisions 96 Sri Lanka National Report on Disaster Risk, Poverty and Human Development Relationship Box 12 : Until the year 2002, the annual average number of appear to occur in the districts of Badulla, Conclusions on landslide records did not exceed 50. However, the Ratnapura, Nuwara Eliya and Kegalle. People Distribution and data shows a sudden increase in the occurrence affected, loss of life, damage to houses and crop Impacts of of landslides during the years 2003-2008. Further, loss also appear to take the same trend with only Landslides landslides are most prone to occur in the months the above mentioned districts being most of November, December and January. With affected. respect to spatial distribution, most landslides 97.