Scale-invariant property of the total source basin area

Understanding the organization of channel networks requires indicators that remain consistent across observational scales. This study examines the scale-invariant property of the total source basin area, formulated as the product of the number of sources and the mean area of source basin. Using the digital elevation model of the Seolma Creek experimental basin in Korea, we generate 889 realizations of channel networks under varying threshold areas and apply the Bai-Perron procedure with the Chow test to detect structural breaks. The results reveal that distinct scaling regimes emerge, corresponding to ephemeral and perennial channel networks, with breakpoints in the number of sources marking the transitions. While the number of sources is highly sensitive to variations in threshold area, the mean area of source basin remains relatively stable, and their compensatory interaction produces the observed invariance of the total source basin area. Notably, ephemeral channel networks retain a constant portion of drainage area as the total source basin area despite seasonal or event-driven variability, whereas perennial networks deviate from this balance. These findings provide an explicit mechanistic rationale for the invariant properties of source basins previously reported in the literature and establish the total source basin area as a robust geomorphologic indicator for analyzing the dynamic behavior of fluvial systems. The approach also offers a framework to evaluate the influence of external forcing such as climate variability on river basin structure. • Total source basin area shows scale-invariant behavior in channel networks. • Bai–Perron procedure detects regime shifts between ephemeral and perennial streams. • Ephemeral networks maintain constant basin area despite threshold variability. • Perennial networks deviate from invariance due to structural breaks in scaling. • Total source basin area is a robust geomorphologic indicator for fluvial dynamics.