Regional Statistical Models for the Estimation of Flood Peak Values at Ungauged Catchments: Peninsular Malaysia

Abstract

Multivariate regional statistical models were developed to estimate flood peak values of various return periods in the Peninsular Malaysia. Annual maximum flood peak data were collected, screened, and analyzed to identify the river gauging stations' potential to produce identical flood frequency curves. The Peninsula was divided into 10 flood regions. The mean annual flood (MAF) for each region was considered as the function of catchment area (A) and mean annual rainfall (MAR). The regional equations exhibited good coefficient of determination (R2). Except for the west of Johor Baru State (Region F6), which showed an R2 value of 0.874, other regions had values greater than 0.90. The regions located along the eastcoast of the Peninsula exhibited better coefficients of determination compared with those for the westcoast, owing to the influence of the northeast monsoon along the eastcoast. Mean index errors (MIEs) with respect to the actual MAF of each flood region are provided to rationalize the design flood peak values to minimize the uncertainty in the predictions. Flood frequency values for the lower, mean, and upper limits were proposed to reduce the effect of outliers and uncertainty in prediction of flood peak values. Knowing the catchment area and MAR of the regions, the design flood peaks of various frequencies can be estimated for the rural ungauged catchments in the Peninsula.