Impact of stream network structure on the transition break of peak flows

The primary objective of this study was to investigate the cause of the transition break in the scaling relationship graph of peak discharge vs. drainage area. Watershed geomorphologic and hydrological data from eleven nested watersheds in the Komarovka River Basin in Russia were collected for analysis. A series of numerical experiments were conducted using a digital elevation model and a geomorphology-based runoff model to investigate the variation of the upstream drainage areas and peak discharges at specified sampling locations on the stream network. The results indicated that when a large tributary flowed into the mainstream, an abrupt increase in the drainage area was observed in the graph of drainage area vs. distance to mainstream outlet. The reason is that the drainage area of the tributary relative to the drainage area of the mainstream at the location which the tributary joins in is large. The abrupt change corresponded to the transition break shown in the graph of peak discharge vs. drainage area, which was an indication of the scaling relationship transferring from linearity to nonlinearity. The cause of the transition break had been verified by using hydrological records obtained from the Komarovka River Basin and successfully simulated by applying the geomorphology-based runoff model.