Natural Disaster Risks in Sri Lanka: Mapping Hazards and Risk Hotspots Lareef Zubair and Vidhura Ralapanawe, Upamala Tennakoon, Zeenas Yahiya, and Ruvini Perera
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Chapter 4 Natural Disaster Risks in Sri Lanka: Mapping Hazards and Risk Hotspots Lareef Zubair and Vidhura Ralapanawe, Upamala Tennakoon, Zeenas Yahiya, and Ruvini Perera Introduction SL Rs 89 million (approximately US$1 million), whereas floods accounted for only SL Rs 7.5 million. The goals for this case study of natural disasters in Sri The prevalence of drought may be surprising given Lanka were (1) to examine the methodologies needed for that Sri Lanka receives an average of 1,800 mm of rain- subnational assessments of hazard, vulnerability, and fall annually. However, it is distributed unevenly both hotspots; (2) to assess the interplay among hazards and spatially (figure 4.2.a) and temporally (figure 4.2.b). A vulnerability; and (3) to assess the consequence of com- large part of the island is drought prone from February binations of multiple hazards and vulnerability factors. to April and, if the subsidiary rainy season from May In the terminology used here, a “natural disaster” occurs to June is deficient, drought may continue into Sep- when the impact of a hazard is borne by “elements at tember. In our analysis, we use a regionalization of Sri risk” that may be vulnerable to the hazard. The elements Lankan climate into four climatologically homogeneous considered in this study are simplified into categories of regions (Puvaneswaran and Smithson 1993)—western people, infrastructure, and economic activities. and eastern slopes and northern and southern plains— Sri Lanka has an area of 65,000 square kilometers as shown in figure 4.2.a. and a population of 18.7 million (Department of Census During the time frame of the study, disaster man- and Statistics 2001).The principal topographic feature agement has been carried out in Sri Lanka by the Depart- is an anchor-shaped mountain massif in the south- ment of Social Services under the Ministry of Social central part of the island (figure 4.1). The topography Services. Relief work for disasters is the responsibility and differences in regional climate (figures 4.2 a and b) of the parent body, the Ministry of Social Welfare. The are underlying causes of the contrasts in many facets of Government of Sri Lanka is currently revising its orga- the island. nizational structure for dealing with and planning for The most frequent natural hazards that affect Sri natural and manmade disasters. Lanka are droughts, floods, landslides, cyclones, vector- Our analysis is carried out in the context of civil wars borne epidemics (malaria and dengue), and coastal ero- that, together, extended from 1983 to 2002. During this sion (Tissera 1997). Tsunamis are infrequent but have period, natural disasters accounted for 1,483 fatalities, caused severe damage. Recent understanding of the tec- while civil wars accounted for more than 65,000. War tonics of the Indian Ocean region points to an increas- has devastated infrastructure and communities’ ability ing risk of earthquakes. The risk of volcanoes is small. to deal with hazards, reduced incomes, weakened safety Here, we have addressed only those hazards related to nets, and undermined capacity to recover from hazard droughts, floods, landslides, and cyclones. We are map- events. For example, there has been a severe toll on hos- ping spatial risks of epidemics in a separate project to pital availability. Although there has been peace since develop an early warning system. 2002, longer-term consequences such as unexploded Drought is the most significant hazard in terms of landmines, war orphans, and the war-disabled continue. people affected and relief provided. The relief dis- The availability of data on hazards and vulnerability is bursements for drought between 1950 and 1985 were restricted in the war zones. The vulnerability analysis 109 110 Natural Disaster Hotspots Case Studies Figure 4.1. The district boundaries of Sri Lanka are shown over the topography Natural Disaster Risks in Sri Lanka: Mapping Hazards and Risk Hotspots 111 Figure 4.2.a. The average annual rainfall climatology estimated based on data from 284 stations in the period between 1960 and 1990. Homogenous climatological regions as proposed by Puvaneswaran and Smithson (1993) are overlaid. 112 Natural Disaster Hotspots Case Studies Figure 4.2.b. The average monthly rainfall between 1869 and 1998 for Sri Lanka Disaster-Related Data: The sources of data were the Sri Lanka Department of Social Services, Sri Lanka Depart- ment of Census and Statis- tics, and the Central Bank of Sri Lanka. These data were of varying resolutions, ranging in scope from the district level (droughts, floods, and cy- clones) to the DSD level (later instances of flood) to the GND level (landslides). Most dis- aster incidence data also con- tained relief expenditures. is complicated by the two-decade-long war. While the Climate Data: Data were obtained from the Sri Lanka precision of our analysis may be affected by the history Department of Meteorology and secondary sources. of war, vulnerabilities created by the war make efforts Although the country has around 400 functioning rain- to reduce disaster risks all the more important. fall stations, only a subset of these possesses uninter- The specific objectives for this study are as follows: rupted records. The records in the Northern Province were limited over the last two decades because of war. • To undertake a subnational analysis of droughts, We used data from 284 rainfall stations from 1960 to floods, cyclones, and landslides; 2000 to construct gridded data at a resolution of 10 km. • To assess vulnerability to these hazards at the sub- Using 1960 to 1990 as the base period, monthly cli- national level; matologies were calculated. Monthly anomalies were • To assess multihazard risks and hazard hotspots at calculated by deducting the climatology from observed the subnational level; and values (figure 4.2.a). • To assess methodologies for incorporating climatic information into hazard analysis. Hydrological Data: Data were obtained from the Sri Lanka We shall describe the data that were used, the method- Department of Irrigation and through secondary sources ologies used for hazard and vulnerability assessment, for monthly river flow measurements at 140 gauging and the analysis of multihazard risk in the following stations. These data had numerous gaps. sections. Landslide Hazard–Related Data: Data were obtained through the National Building Research Organization Data of Sri Lanka. In-Country Data Population, Social, Economic, and Infrastructure Data: The Department of Census and Statistics provided popula- The administrative divisions in Sri Lanka are provinces, tion data. Data at the DSD level were selected for com- districts, divisional secretariat divisions (DSDs), and parison and analysis. Gross domestic product (GDP) Grama Niladhari (Village Officer) divisions (GNDs). measures, including regional GDP, were obtained from There are 9 provinces, 25 districts, 323 DSDs, and 14,113 the Central Bank of Sri Lanka. GNDs, organized hierarchically. Food Security Data: An assessment of food security in Sri Lanka was conducted under the Vulnerability Assess- Natural Disaster Risks in Sri Lanka: Mapping Hazards and Risk Hotspots 113 ment and Mapping Program of the World Food Pro- four instances of epidemics. EM-DAT identifies 9 gramme (WFP), Sri Lanka office. The identification of droughts, 2 landslides, 3 cyclones and storms, and 33 DSDs with three levels of food insecurity was obtained flood events (including floods caused by the cyclones). from their maps. The dataset contains dates and affected areas and people. The United Nations Environment Programme/GRID Hazards and disaster records had good identification (UNEP/GRID) datasets include global cyclone tracks for of where these occurred, but often only the year when the period from 1980 to 2000. these occurred was available. The temporal resolution was improved by interrogation of multiple data sources and by consulting government officials. Exposure and Vulnerability Global Data Sources Exposure and vulnerability may be assessed for the three categories of elements at risk—people, economic Hazard Data––Floods: Dartmouth Flood Observatory activity, and infrastructure. carries an archive of large flood events from 1985 onward. This database contains specific dates of the floods, sever- ity class, and affected area. However, the spatial reso- People lution is coarse, as the data have been derived from the Population: The population of Sri Lanka was 19.2 mil- district level. lion in 1998 (293 persons per km2) with an uneven dis- tribution (figure 4.3). Fifty-five percent of the population Climate Data: The data available at the International is concentrated in 20 percent of the land area (Depart- Research Institute for Climate and Society (IRI) Data ment of Census and Statistics 2001). Thirty percent of Library with long coverage for Sri Lanka is lower in the population resides in urban areas. The least-popu- resolution (250 km grid). lated districts (covering 40 percent of the island) host 10 percent of the population. In these districts, population Exposure Data––Population, Social, Economic, and Infra- density ranges from 35 to 100 people per km2, which is structure Data: Center for International Earth Science still high by global standards (De Silva 1997). The high- Information Network’s (CIESIN’s) Gridded Population est population is in the Colombo, Gampaha, and Kalu- of the World (GPW2) dataset contains population data tara districts of the Western Province. There is a secondary on a 5 km grid. The gridding methodology of GPW2 population center in the Kandy District in the Central utilizes district-level population data. “Landscan Province and in the Galle District along the southern 2001” contains gridded population data on a 1 km coast. The high density of people in the wet parts of the grid calculated using population, roads, slope, land island increases the number of people who are vulnera- cover, and nighttime lights. ble to floods and landslides. Impoverishment and mortality are direct consequences Vulnerability Data: The United Nations Development of, as well as contributors to, natural disasters.