WEATHER·CHANGING PATTERN OF THE RECENTLY EARTH·SLlP AFFECTED AREA OF PUWAKGAHAWELA

Abstract

The village of Puwakgahawela with its 60 households and 342 inhabitants in the ImbulpeDivisional Secretariat under the Balangoda Electorate in the Ratnapura District of SriLanka was recently faced with a great disaster due to an earth slip. While several factorsthat had contributed to this earth slip were identified the weather-changing pattern(rainfall and temperature) was considered the most crucial among them. Therefore, inorder to ascertain the scientific information about the earth movement vulnerability of thearea, the Sabaragamuwa University Centre for Environment and SustainableDevelopment (SUCEDS) has implemented a research study that aims at investigating therainfall pattern, making useful forecasts about future disasters, and finding out therecurrent interval of similar weather conditions (if there will be any) by decomposing therainfall model developed by the SUCEDS. In this regard trend analyses of minimum,maximum, and average temperatures of the Puwakgahawela area were carried out whilepaying attention to the secondary data available

For the forecasting of rainfall and temperature a linear trend model has been installed.The accuracy of fitted values was checked using the mean absolute percentage error(MAPE) and the mean absolute deviation (MAD). The MAD of the fitted trend line ofrainfall data is 222.3 mm and the MAPE is 11.5%. According to these data, there is anincreasing trend in the rainfall in the Puwakgahawela area. The predicted recurrentinterval of the rainfall is five years within which two peaks and two falls have beenobviously identified.

According to the negative regression coefficient (- l.13x 10.2) of the minimumtemperature model for the area, there will be an approximately I "c reduction in theminimun. temperature for the period of 8 years (1992-2000). Th~ positive regressioncoefficient of the model (5.93x 1003) denotes that there will be an approximately 0.6 0 Cincrement in the maximum temperature in a period of 8 years. The negative regressioncoefficient (-268 x 1003) of the fitted linear model of average temperature, theapproximate predicted reduction of the average temperature will be 0.25 °c for a periodof 8 years. Therefore, in conclusion, the minimum, maximum and average temperaturesof the focal area show decreasing, increasing and decreasing trends respectively.