Home Articles Mapping the Vulnerability of Coastal Public

Mapping the Vulnerability of Coastal Public

PGRNI Pussella
Department of Cartography, Photogrammetry, Remote Sensing and GIS
Faculty of Geomatics, Sabaragamuwa University of Sri Lanka, P.O. Box 02, Belihuloya, SRI LANKA
Postgraduate Institute of Science, University of Peradeniya, Peradeniya, SRI LANKA
Tel: +94452280031, +94773314079
Fax: +94452280010
Email: [email protected]

With the intention of moving the population away from the hazardous areas, in 2004, the government of Sri Lanka established the “No Build Coastal Buffer Zone” of 200m in the North and East coasts of the country and 100m elsewhere. It was announced that residents within the zone would not be permitted to rebuild damaged or destroyed buildings which were totally destructed by Tsunami waves. In practice, this has proven extremely difficult to enforce due to both public and political unawareness. This study mainly attempts to analyze and mapping the vulnerability of the coastal public of Hambantota area. According to the results, the study reveals that several reasons for the Natural Vulnerability, as altitude is below than 5m from the Mean Sea Level, Damages on the natural barriers such as coastal vegetation, coral reefs, sand dunes, due to various human activities and mainly due to Tsunami waves as well as the area is directly open to sea. Considering these factors, the study identified that the people are more vulnerable both economically and naturally. The government should take an immediate action to overcome this problem.

The coast is the home to a third of the population of Sri Lanka and the highly productive ecosystem is an important base for the growth of the country. Most of the people derive their livelihood from economic activities in the coastal zone. It accounts for nearly 80 percent of fish production and 70 percent of industrial output of Sri Lanka [1]. The coast line of Sri Lanka extends a length of about 1,585 km [2]. The coastal region includes terrestrial ecosystems, mangroves, lagoons and estuaries, shoreline ecosystem, coral reefs, etc. Coastal erosion has been a severe problem over the years especially in the south, west and north-western coast in Sri Lanka. It has discovered that the western and south western coast of Sri Lanka alone loses between 200 000 and 300 000 square meters of beach a year due to storms and high waves [1]. At certain locations, the net erosion has been recorded up to 1 m per year [2]. On the other hand, accretion rate have not exceeded 0.1 m per year, except in the north and east where the rate is 0.3 m per year [2]. The average net mean rate of erosion for the entire country is varies from 0.2 to 0.35 m per year [2]. The eroding coastline especially threatens the economic activities on the densely populated costal regions.

With a comprehensive approach to the coastal resources management in Sri Lanka, the Coast Protection Unit was established with the Colombo Port Commission in 1963. It recommended a more management oriented approach in 1971 after analyzing the problems associated with coastal development. In 1978, the government of Sri Lanka established a Coast Conservation Department within the Ministry of Fisheries to initiate steps to halt the continued deterioration of the coastal zone. The government enacted the Coast Conservation Act No. 57 in 1981. The Coast Conservation Act required the Director of Coast Conservation to have a survey made of the Coastal Zone and, on the basis of the results of the survey, to prepare a Comprehensive Coastal Zone Management Plan. It also established the Coast Conservation Advisory Council which reviews coastal management problems of significant concern and advises the Minister in charge of Coast Conservation. The Act stipulated that all development activities in the coastal zone be subject to permits. One of the main elements of the management plan was a national permit-issuing program, which required construction setbacks within the 300 meter coastal zone. The law specifically states that this setback is to protect the people and their property from sea based disasters. A permit is required for all development activities that are likely to alter the physical nature of the Coast Zone. But fishing, cultivation of crops, planting of trees and other vegetation, and construction and maintenance of coastal protection works by the Coast Conservation Department may be engaged in without a permit within the Coastal Zone.

The recent Tsunami highlighted the need of a system of coastal zone management. While in the process of reconstruction and reformation, the possibility of vulnerability zones in coastal areas came into discussion and the policy makers started to pay much attention to this matter. Unfortunately, they considered only about the Distance from the coastal line without having any knowledge of important factors such as Height above Mean Sea Level, Socio Economic Data in the area, Natural and Man made Barriers etc. to define the vulnerability zone in the coastal areas in Sri Lanka. After several discussions, the government of Sri Lanka established “No Build Coastal Buffer Zone” of 200m in the North and East coasts of the country and 100m elsewhere from the high water mark. This demarcation was meant for the benevolence and safety of the present and the future generations and the decision was not based on any narrow political agenda (Silva, 2007). In practice this has proven extremely difficult to enforce over the years due to the unawareness of the public. It is clear that while the law should be enforced, public awareness is the most important thing. Certainly, the key to gaining support for such practices lies in building both local and political awareness. One of the major obstacles in enforcing these buffer zones was the lack of local support. Therefore there should be a reasonable concept to formulate policy reforms to get the maximum support of the communities in the coastal zone.

In total, it has been estimated that up to one million people have been affected by the Tsunami. This represents 5% of Sri Lanka’s entire population. Therefore, there is an urgent need to rebuild Sri Lanka’s shattered infrastructure. It is necessary to look to the environment and conditions which people will face in the future and the risks and uncertainty inherent to this. There must be recognition of the need to adopt and respond to changing environmental and physical conditions in the coastal zone and the disaster preparedness of how we are to plan and operate. This includes taking account of the likelihood of natural hazards such as floods, storms and cyclones occurring, as well as human-induced risks associated with processes of climate change, environmental degradation, oil spills as well as marine and coastal pollution. The main objective of the study was to analyze and mapping the vulnerability of the coastal public who are residing within the government established “No Build Coastal Buffer Zone” of Sri Lanka for natural hazards such as Tsunami, Coastal Erosion etc.


3.1 Site Selection
Depending on the socio economic and physical characteristics, the coastal area of Hambantota was selected for the study.The district has an area of 2609 square kilometers and a shoreline of 130 km. According to the Central Bank of Sri Lanka Annual Financial Statement -2005, Hambantota ranks as the third poorest district in the country and the poorest coastal district in the country, recording 32 percent of its people as poor. The livelihoods of the area are diverse, with the main economic activities in the coastal areas comprising of fishing as well as agriculture, trade and services. A substantial share of the services caters to local and foreign tourists. The economy of Hambantota revolves around trading and services activities to a large extent. Official statistics collected by the District Secretary and reported by the District Disaster Management Committee (DDMC) indicate that the tsunami impacted 16,994 families, caused more than 3,000 deaths and damaged or totally destroyed more than 4,000 houses in the Hambantota district. The total damage was estimated to be SLR 23 billion. The Ministry of Fisheries reported that 92 percent of the fishing fleet was affected by the disaster and it was reported that damage to the agricultural sector included damage to about 350 hectares of paddy and 36 hectares of other field crops.

3.2 Data collection & Analysis
Two types of data were collected for the study. Socio economic data gathered from randomly selected 50 families who are residing in the 100m buffer zone limit, using a semi structured questionnaire and field surveys as primary data sources. Existing maps and High resolution Satellite images were used to collect the topographic data of the region. The data were analyzed using Geographical Information Systems (GIS) and Statistical tools. Geographical Information Systems (GIS) have been used extensively in storing, processing and displaying coastal information. They offer significant advantages such as the ability to handle large databases, and to integrate data from a wide range of sources.

The study identified two types of major factors which are directly influenced to the vulnerability of the coastal public within the area.

    I. Economical Vulnerability
    II. Natural Vulnerability

4.1 Economical Vulnerability
The economic structure of the Hambantota DS Division is characterised by its rural setting, paddy fields, coconut plantations, inland lagoons, reservoirs, beaches and ocean. The economy is small and centred on agriculture, inland and ocean fisheries and livestock rearing. The industry and services sectors are young and confined to agro processing, manufacturing (garments), petty trade and small-scale tourism. Supplies to the main regional and national markets of Matara, Galle and Colombo are small to insignificant. As with the other Divisions in the District affected by the Tsunami, the economy of Hambantota DS Division is strongly agriculture based, including cash crops (mainly paddy), plantation crops (coconut), horticulture, livestock for beef and milk production and inland and coastal fishery.

Aggregate data on employment distribution show over 52% of employment concentrated in the agriculture sector, 10% in Government, 19% private enterprises, largely micro and small manufacturers and small traders and 19% other employment, unfortunately not further disaggregated by the Bureau of Statistics. Within the Division, 35% who are employed by the Government and the private sector can be as summed as those who have formal education certificates or non certificate holders with a reasonable level of formal education (graduates, advanced level and ordinary level certificate holders totaling up to 24%). Based on this assumption, the 77 % who earn less than USD 2 per day (about LKR 6,000 per month) would be engaged in subsistence agriculture, small scale fishery, micro enterprises, and wage labour and have no secondary education.

The study revealed that several factors such as poor land use (35% of the study area), high population density in the urban area, non sustainable and effective use of the natural resources and the damages of Tsunami waves on small and medium enterprises such as fishing, tourism, farming and trading and on infra structure facilities such as transportation, telecommunication, electricity, water supply etc. have being affected severely to the economical vulnerability of the area. The active participation of governmental and non governmental organizations is very essential to uplift the economy of the coastal public to remove the effects of Tsunami on their ways of life.

4.2 Natural Vulnerability
It is clear that the degree of damage by the tsunami waves along the coastal belt of Sri Lanka is not uniform. Wijetunge (2006) identified that the level of vulnerability is attributed to several factors such as the coastal topography, the population density, the construction standards, the type of land use including the density of vegetation and buildings. Wijethunge (2006) remarked that the deepest tsunami wave penetration in the south coast is at Hambantota, up to three kilometers near the salt-pans and particularly around the smaller lagoons and bays. Hungama-Tangalle beach to the west of Hambantota too has recorded notable inundation, especially where tsunami surge waves had been conveyed inland through water bodies opening to the sea such as lagoons and lakes.

A Digital Elevation model (DEM) is a way of representing topography using the raster data model. In a raster data the data is a matrix cell, each cell has a single value of elevation and the raster cell has a specified spatial resolution. It represents the spatial variation of height over a given terrain. DEM data is a basic starting point in most analysis including watershed modelling, rainfall-runoff forecasting, identifying topographic features, visualization of the topography, slope stability analysis and flood forecasting, etc. A DEM was prepared to analyse the topography of the area using contour map with 2m as the contour interval. The coastal public is more vulnerable in the area, since it is a comparatively low land area.

The most significant environmental damage from the tsunami is expected to be marine-related, especially in inter-tidal and sub-tidal areas. Such damage could cause changes in the coastal marine ecosystems, as well as immediate loss of natural resources such as fish, lobsters and crabs. Many coral reefs may have been reduced to rubble in certain places due to the crushing force of the waves. There could also be significant contamination as a result of land runoff of wastes and pollutants, debris, soil and organic matter. In addition, mangrove areas, which protected property and lives during the tsunami, are now damaged.

Throughout the regions affected by the recent tsunami, scientific evidence has shown that less-developed areas having sufficient natural coastal barriers such as healthy ecosystems of mangroves, sea grasses, sand dunes, and coral reefs were protected from the tsunami and remained largely intact, while areas developed with hotels and other buildings along the coast suffered greatly in the absence of such natural buffers. Marmiit and Wijayaweera (2006) have estimated the value of mangrove ecosystems as shoreline buffer at the event of extreme disasters and indicated that the costs of damages to livelihood and property in areas having a degraded and disturbed ecosystem are approximately ten times the costs of damages in the areas having a well managed and functioning coastal ecosystem. Hambantota Sand dune system with dense coastal forest has proved their value and capability as a natural protection for people and their properties in a situation like tsunami. There were severe damages in near-shore areas, including to seashore Pandanus (Wetakeyia) and creeper vegetation, and inland palmyrah trees, with near-shore coconuts less affected as were inland economic trees. Casuarina plantations proved vulnerable to tsunami damage and by themselves had little protective value, though in places they helped stabilise sand dunes which themselves moderated the tsunami. Estuaries often acted as channels of entry for the tsunami, facilitating damage and salt water intrusion far inland. Front-line mangroves were badly damaged, while deeper mangroves were left intact and dense mangroves converted the wave into a flood. Lagoons absorbed tsunami energy, but in doing so, seasonal sand barriers were lost, their banks were scoured, and mangroves at their entrances were dislodged, but they were otherwise little affected and/or recovered quickly. Large, vegetated sand dunes stopped tsunami intrusion to a considerable extent. Beaches were eroded and scoured losing width and height mainly from tsunami back-wash. Large volume of debris was accumulated on most beaches.


The study has selected following 3 sites for further analysis of the vulnerability of the coastal public within the 100m buffer zone, based on criteria such as the density of the population, economical strength of the area to the national economy, human activities in the area, presence of natural barriers and the damages by the tsunami waves. The areas are having following features in general.


Thelwatta/ Peraliya


Densely populated area

Less Population

Less Population

Economically strength

Less Economical strength

Economically Less Strength

More Human Activities

Less human activities

Less human activities

Well strength in Natural Barriers

Less Strength in Natural Barriers

Well strength in Natural Barriers

Considerably Less damages by the Tsunami waves

More damages by the Tsunami waves

Less damages by the Tsunami waves

Considering above factors, the study concluded that the coastal public of the study area are more vulnerable naturally and economically. The government of Sri Lanka should pay much more attention on this. The study reveals that when designing a vulnerable zone for the country, natural, social and economical factors should be considered to get the maximum support of the coastal public. Sustainable use of natural resources is very important in the development process.


  • /news/1999/nr1999125.asp (Downloaded, 10.03.2005)
  • (Downloaded 08.03.2007)
  • https://www.sacep.org/html (Downloaded 08.03.2007)
  • Samaranayake, RADB, 1995. Regulatory control of coastal development in Sri Lanka. Coastal Conservation Department of Sri Lanka.
  • Coast Conservation Act No. 57, 1981, the government of Sri Lanka.
  • Mamiit, RJE, Wijayaweera, K, 2006. Shore line protection value and social dimensions of mangrove ecosystems in coastal villages affected by the 2004 tsunami in Sri Lanka, Joint Institute for marine and atmosphere research, University of Hawaii Manoa, Honalulu, USA. Proceeding of International Forestry and Environment Symposium, 2006
  • Wijethunge, JJ, Tsunami on 26 December 2004: Spatial distribution of Tsunami height and the extent of inundation in Sri Lanka. Department of Civil Engineering, University of Peradeniya, Peradeniya, Sri Lanka.
  • De Silva, Ranjith Premalal, Towards a national spatial data infrastructure, Geo-Informatics Society of Sri Lanka, University of Peradeniya, Peradeniya, Sri Lanka.
  • Central Bank of Sri Lanka Annual Financial Statement – 2005 (Downloaded on 08.03.2007

The authors wish to acknowledge to Genesis Software (Pvt) Ltd. for their great contribution to the success of the study and also to the Sabaragamuwa University of Sri Lanka hence this investigation study received the financial support from the Research grant scheme of the university under the Grant Number SUSL/RG/2007/01.