Lithologic control on the multifractal spectrum of river networks.

Previous observations on some natural river networks showed the similar values of the support fractal dimension and the information entropy in basins having similar source rocks. In the present work, lithologic control on river network multifractality is investigated through the reconstruction of the spectra belonging to two classes of different lithology: the plutonicmetamorphic class and the coherent sedimentary one. Two computational methods of the generalised fractal dimensions and multifractal spectra are illustrated and applied to river networks of the Calabria region (Southern Italy). It is shown that an increment of both the fractal dimensions and the Lipschitz-Ho¨lder exponents of singularity occurs when passing from a coherent sedimentary to a plutonic-metamorphic river network. The importance of this finding emerges from the direct link between flood hydrographs and multifractal spectra, as expressed in the Multifractal Instantaneous Unit Hydrograph (MIUH): the increment of the multifractal parameters produces an increment of the flood peaks.