Assessment of tsunami damage on the coastal vegetation in 3 selected locations in Yala National Park

Abstract

Tsunami, the killer wave swept nearly two thirds of the coast of Sri Lanka on 26th of December, 2004.About 40,000 people died and around 500,000 people were displaced, more than 119,000 housesdamaged either fully or partially. About 13 coastal districts were directly affected, the north and eastsuffered the brunt of the blow accounting for about 2/3 of deaths and 60% of displacements. In termsof ecological aspects, with the exception of few species, most of the vegetation suffered total orpartial death, lagoons, estuaries, coral reefs, sea grass beds, salt marshes and mangroves experiencedthe damage at varying levels.

A study was conducted in 3 Tsunami affected locations in Block 2 of the Yala Natoinal Park with aview to assess the condition of the vegetation more than 1.5 years after the incident. In each site, 3plots which were lOx 10m were demarcated the vegetation including trees, shrubs and groundvegetation was assessed. A tsunami non affected site in close proximity to the study sites was takenas the control. Direct observations were also made on the dead plants, regenerated one, other externaldifferences observed (color changes etc.). Shannon's Diversity Index (Diversity, Evenness andDominance) and Stand Variables such as Relative Frequency and Relative Density were calculatedusing the data. In addition to the vegetation, soil and water were also assessed for pl-I, conductivity,salinity etc. The measurements were repeated twice in the experimental period of 6 months

51 species which belongs to 30 families were observed (without ground vegetation) in the 27 plotsstudied. The stand variables did not differ significantly between the 3 sites studied. However, somespecies had higher proportional abundances in Tsunami affected sites compared to those which werenot affected. Kathurupila (Tephorosia purpurea), Lunuwarana (Crateva religiosa), Ranawara(Cassia auriculata) were more prominent in the Tsunami affected sites in Mahaseelawa comparedto the non affected sites in the same location. Patassa was seen abundantly in non tsunami affectedsites. Korakaha (Memecylon umbellotumi and Katupila (Tephorosia purpurea) were most abundantamong the shrubs in tsunami affected areas while Wal pichcha (Momordica diociai was prominentin unaffected areas. In the Patanangala site, among the trees Elabatu was' seen quite prominently(Solanum xanthocarpum). Attana (Datura mete!), Wal kochchi (Croton bonplandianuss recordedthe highest proportional abundance. In non tsunami affected areas Gandapana (Lantana camaraiand Maduruthala (Hortinia horibunda) recorded the highest abundance. In Buthawapitiya siteLunuwarana (Crateva religiosa) , Ranawara (Cassia auriculatai, Katupila (Tephorosia purpurea),and Pila (Tephorosia purpurea ). Andara (Acacia leucophloea) was seen in both tsunami affectedand non affected areas.

In general, four species were observed to be dominant in the vegetation in the Tsunami affected areasie, Walkochchi (Croton bonplandianusy, Attana (Datura metals, Kathurupila (Tephorosia purpurea).Leguminosae and Euphorbiaceae were the most dominating families in species of this Tsunami affectedsites and Rubaceae and Oleaceae were the most dominant species in Tsunami not affected areas.

The water quality showed significant variation between the sites studied while soil parameters werenot significantly different. The electrical conductivity of water was highest in Bathuwapitiya site pHdid not show significant difference between sites. Buthawapitiya recorded high salinity values comparedto other sites. Soils did not record values which were significantly different.

(SME 's were considered to be business that had employed less than 25 workers and less thanRs.5 Mn turn over in immediately preceding 12 months period.)