Floods - Extreme Events: A Physical Reconstruction and Risk Assessment - page 72

Figure 3.10. Aerial photographs of Green gully (Thule Lagoon Reach) (top) and
modern Murray River (bottom) Australia at the same drainage area and scale. Green
Gully was the ancestral Murray River prior to 12 000 years BP (Page et al. , 1996 ). Note
the much larger meander wavelength of the ancestral Murray River (top image)
compared to the modern Murray River. Photograph courtesy of Dr Ken Page, Charles
Sturt University.
are responsible for meander wavelengths in alluvial channels. This is because
alluvial channels are relatively easily eroded during a flood. In some locations,
relict alluvial channels display meander wavelengths that are considerably larger
than those forming in modern channels (Fig. 3.10). The suggestion is that these
relict channels were formed by floods of greater discharge but with approx-
imately the same frequency of occurrence as the floods forming the smaller
channels today. The clear implication, therefore, is that flood discharges have