Larhyss Journal, ISSN 1112-3680, n°53, Mars 2023, pp. 183-197
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© 2023 Bong C.H.J. and al.; This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
TREND AND STATISTICAL ANALYSIS OF ANNUAL MAXIMUM DAILY RAINFALL (AMDR) FOR SARAWAK RIVER BASIN,
SARAWAK, MALAYSIA
BONG C.H.J.1*, LIEW S.C.2, SIM J.E.3, TEO F.Y.4
1 UNIMAS Water Centre, Faculty of Engineering, Universiti Malaysia Sarawak, Sarawak, Malaysia
2 Faculty of Engineering, Computing and Science, Swinburne University of Technology Sarawak Campus, Sarawak, Malaysia
3 Road and Civil Engineering Asset Branch, Public Works Department of Sarawak, Sarawak, Malaysia
4 Faculty of Science and Engineering, University of Nottingham Malaysia, Selangor, Malaysia
Research Article – Available at http://larhyss.net/ojs/index.php/larhyss/index Received January 2, 2023, Received in revised form March 8, 2023, Accepted March 10, 2023
ABSTRACT
The Sarawak River Basin is one of the major river basins located in the southern part of Sarawak, Malaysia, and has experienced frequent extreme rainfall resulting in flash floods in recent years. This study aims to carry out trend and statistical analysis of annual maximum daily rainfall (AMDR) for 10 rainfall stations distributed evenly in the basin from 1975 to 2020. From the analysis, the AMDR records high variability for most of the rainfall stations, with the month of January having the highest occurrence of AMDR events. The linear regression plot of the mean AMDR showed a slight decreasing trend over the past four decades. The threshold rainfall value of 180 mm was used to perform frequency analysis, and the result shows that the return period for daily rainfall exceeding 180 mm was 2.71 years. The occurrence probability of the flood event at least once in 1, 2, 3, 4 and 5 years was 0.37, 0.60, 0.75, 0.84 and 0.90, respectively. A frequency curve based on the mean AMDR data with Gumbel distribution fitting was also developed from the current study and can be applied to the planning and design of flood infrastructures in the basin.
Keywords: Annual maximum daily rainfall, Extreme events, Frequency analysis, Rainfall trend, Urban drainage
