A hydrological-year stratified regionalization framework for sediment rating curves in the largest tributary of the Mekong River

Study region The Mun River Basin in Thailand, the largest tributary of the Mekong River. Study focus Sparse sediment monitoring limits reliable sediment-load estimation across the Mun River Basin. Sediment rating curves (SRCs) provide a practical means of estimating sediment loads from discharge, but conventional static SRCs do not adequately represent interannual variability in sediment–discharge relationships. This study develops an advanced SRC regionalization framework that integrates hydrological-year stratification (flood, normal, and drought years) with regression-based and catchment-similarity approaches to improve estimation under limited sediment observations. New Hydrological Insights for the Region Hydrological-year stratification showed that SRC parameters vary among flood, normal, and drought conditions. Classification using station-specific 2-year and 10-year return-period peak-flow thresholds separates contrasting hydrological regimes and indicates that interannual flow variability exerts a stronger influence on sediment-response behavior than basin-wide land-use change. Regionalization suitability also depends on catchment characteristics. Regression is more appropriate for gentler catchments with S c < 6.0% and K USLE x C USLE > 0.05, where sediment response is governed mainly by integrated basin-scale attributes. Catchment similarity is more suitable for steeper catchments with S c > 6.0% and K USLE x C USLE < 0.05, where sediment generation and delivery are more spatially heterogeneous. These findings show that both hydrological regime and catchment physiography should be considered when regionalizing sediment–discharge relationships in the Mun River Basin.