PARAMETER-PARAMETER CURAH HUJAN YANG MEMPENGARUHI PENAKSIRAN INDEKS EROSIVITAS HUJAN DI SRI AMAN, SARAWAK

Abstract

The soil erosion in some areas can be serious and may continue for such a period that most fertile soil may be lost. Rainfall is the main factor that may result soil erosion.  The rainfall erosivity factor used in the Universal Soil Loss Equation (USLE) is ability of rainfall to cause soil erosion.  However, there is insufficiency of information available on the estimation of rainfall erosivity index and its rainfall parameters in Sarawak.  The aims of this study were to estimate rainfall erosivity index based on Bols Formula and to examine the rainfall parameters influencing its estimation in Sri Aman, Sarawak, East Malaysia.  The climate data such as monthly rainfall, monthly raindays, and maximum rainfall for the last 27 years (1983-2009) were collected from Meteorology Department Malaysia (Sarawak Branch).  The annual rainfall erosivity index during the analysed period was the highest in 1995 (4194.10) and the lowest in 2006 (1832.37).  The highest and lowest values of annual rainfall had also recorded in these years (425.81 cm in 1995 and 236.43 cm in 2006).  The average annual rainfall, raindays, maximum rainfall, and rainfall erosivity index were 336.50 cm, 227 days, 11.23 cm, and 2929.18, respectively.  The average rainfall erosivity index on monthly basis showed that the maximum value was 348.31 in January and the minimum value was 169.00 in June.  The estimation of annual rainfall erosivity index was very influenced by rainfall parameters, namely, annual rainfall, annual raindays, and maximum rainfall.  The information on rainfall erosivity index is useful as a basis for planning and designing appropriate soil and water conservation practices in Sarawak.