Discharge–Sediment Regimes in Peninsular Malaysia: A Multi–Scale Analysis Based on National Datasets

Tropical monsoon rivers can export a disproportionate share of sediment during short–lived high–flow events, yet humid, low–relief regions remain underrepresented in global discharge–sediment syntheses. Here we compile national daily discharge (Q) and suspended–sediment discharge (Qs) records from Peninsular Malaysia and quantify fluxes, yields, and discharge–sediment coupling across 12 river basins from seasonal to interannual scales. Across catchment outlets (n = 30), runoff export is comparatively buffered (water yield, WY ≈ 240–7691 mm yr^-1), whereas sediment export is highly uneven and episodic (sediment yield, SY ≈ 46–985 t km^-2 yr^-1), with a small number of rivers contributing most monitored sediment flux. Basin attributes define a dominant relief–to–lowland regional gradient, but this structure explains only a modest share of SY variability (R² ≈ 0.15), , suggesting that sediment yield is strongly modulated by basin-scale processes beyond regional structure. Across outlets, SY scales with WY as a power law (SY = 1893.5WY^0.68; R² = 0.30, p = 0.002), but the coupling differs by coast (West: R² = 0.49, p = 0.008; East/South: R² = 0.21, p = 0.082), implying systematic regional contrasts in sediment yield at comparable runoff. Seasonality is strongly monsoon–driven, and sediment export forms the sharper pulse. The wettest three–month period typically carries ~32–68% of annual discharge but ~38–88% of annual sediment. Interannually, discharge varies within a modest range, while sediment export commonly changes several–fold, so moderately wetter years can dominate long–term sediment budgets. Regulation further modifies these dynamics without a single consistent direction, indicating that post–dam sediment delivery depends on basin–specific sediment supply, storage, and connectivity rather than trapping alone.