Evaluation of Rainfall Characteristics of Sungai Brunei Drainage System Under Climate Change / Dayangku Siti Nurul Ain binti Pengiran Ali Hasan

A thesis submitted to Universiti Teknologi Brunei in fulfilment of the requirements for the degree of Master of Science by Research in Water and Environmental Engineering

ABSTRACT

Persistent change in the climate sand weather in Brunei Darussalam has unfavourable impacts to its economy, environssunt and society. In recent years, Brunei has become more vulnerable to flooding. Therefore, it is crucial to comprehend important climate indicators, such as temperature and precipitation to minimise its impacts. The first phase of this study analysed the trend of observed temperature and rainfall in the past by using the linear regression and Mann- Kendall test. The results revealed that all observed temperature and precipitation variables experience significant positive trends at a confidence level of more than 90%. The second phase of this study assessed the performance of statistical downscaling model to downscale GCM results of maximum and minimum temperatures along with precipitation in Brunei Darussalam. It investigated future climate changes based on various scenarios of HadCM3, CGCM3 and CanESM2 with the implementation of bias correction. Monthly sub-model is proved to assess more satisfactorily than annual sub-model. This study revealed inferior correlation with the observed but illustrated acceptable application for generation of future periods 2017-2046 and 2047-2076. This study illustrated that Tmax and Tmin of H3A2 and H3B2 projected to increase significantly up to 0.54°C, by 2076. In the case of precipitation, H3B2 projected an increase in precipitation with no significant negative trend. H3A2 was consistent with CGCM3 and CanESM2 in predicting increasing trend of maximum and minimum temperature associated with decreasing trend of precipitations. CanESM2 with RCP8.5 scenario was recognised as maximum trend of Tmax at a rate of 0.014 °C per year. The highest prediction of average maximum temperatures by 2076 is to increase by 1.4 °C. The same model predicts an increasing trend of Tmin of 0.004 °C per year while the highest trend is seen under CGCM3-A2 scenario which is 0.009°C per year. The highest change predicted for the Tmin is therefore 0.9 °C by 2076. The precipitation showed a maximum trend decrease of 12.7 mm year. It is also seen in the output using CanESM2 data that precipitation will be more chaotic with some reaching 4800 mm per year and also producing low rainfall about 1800 mm per year. These consistent results demonstrate that the climate in Brunei Darussalam is likely to get warmer and drier with sudden heavy downpour in the future.

Thesis (Degree) - Universiti Teknologi Brunei

Includes bibliographical references