LUPIA PALMIERI E., BIASINI A., CAPUTO C., CENTAMORE E., CICCACCI S., DEL MONTE M., FREDI P. & PUGLIESE F.
Geomorfologia quantitativa e morfodinamica del territorio abruzzese: III – Il bacino idrografico del Fiume Saline – Quantitative Geomorphology and Morphodynamics of the Abruzzo Region, Italy: IIIThe drainage basin of the River Saline
Pages 157-176
Abstract
This work is part of a series of wide geothematic researches focussed on the contribution of quantitative geomorpohology to the morphogenetic and morphostructural characterization of the Abruzzo region. The Fiume Saline drainage basin is considered; this river is the final section of the Fino and Tavo rivers, that, after a course of about 40 km join together at about 6 km from the debouching into the Adriatic Sea. The drainage basin of the Fiume Saline develops on the eastern margin of the Apennines and the facing central part of the southern Adriatic foredeep. Main outcrops belong to the deposits of the «Laga Basin», of the «middle-Emilian Pliocene cycle» and of the «Cellino Basin»; locally also outcrop Trias-Paleogene carbonate Units and Miocene calcareousmarly Units. Following methods widely tested, it has been possible to establish the types and intensity of the denudational processes acting in the study drainage basin as well as the morpho-structural assessment of this part of the Abruzzo region. Geological surveys have been concentrated above all on lithological and tectonic features of the basin, considering the morphogenetic and morphostructural ends of researches. Geomorphologic surveys have been directed towards two themes, both having a remarkable importance for morphodynamics of the Abruzzo region. The first theme concerns the denudational processes that affect the different parts of the study basin, with particular attention to instability phenomena. The second theme is represented by neotectonics; in this case researches have been mainly addressed to the identification of tectonic lines present in the study area. Morphometric researches, especially quantitative Geomorphology, supplied an essential contribution to the study of relations among geomorphic elements and geological characteristics; this study has been mainly addressed towards indirect evaluations of solid supply and erosion entity inside the basin. Satisfactory as well are results achieved by morphotectonic researches, among which very interesting are those derived from the statistical analysis of azimuthal distribution of fluvial channels. This analysis also provided important information on effects of mainly recent tectonics on the drainage net configuration, thus allowing to identify also joint and fault systems not always detectable by means of geological surveys. The comparison of data coming from morphographic analyses and quantitative geomorphology allowed to subdivide the whole study basin into different sectors, each characterized by different structural assessment and denudational processes being different in type and intensity. The two main partial basins belonging to the Fiume Saline in general show different morphodynamic conditions. Denudational processes result more widespread and intense in the Fiume Fino basin as to those of the Fiume Tavo, where they appear to be of limited spreading and smaller effectiveness. This different condition is also confirmed by quantitative geomorphologic analysis: the stronger intensity of morphogenetic processes acting inside the Fiume Fino basin goes along with a marked poor organization of the drainage net and with high values of the «denudational index». More in detail geomorphic changes result very vivid on the left slope of the middle-upper part of the Fiume Fino basin. This area records medium-high «denudational indexes» and drainage nets are better organized, following a stronger action of fluvial cutting and of minor spreading of sheet, rill and gully erosion. The right slope shows denudational processes with a minor areal spreading, but the «denudational index» is still rather high. This may be partly explained considering that – even if less widespread – denudational processes are locally very marked and this condition has an obvious weight on solid supply. On the contrary, similar processes are present inside the Fiume Tavo basin only in a subordinated way. Indeed, analyses made for this basin show all together the general lack of areas undergoing rapid geomorphic changes, with the exception of very restricted areas. The morphotectonic study evidenced at what extent the morphologic configuration of the whole drainage basin (Fiume Saline) results conditioned by tectonics, that surely must have acted in a very complex way and with an intensity being very different in the various parts of the same basin. The whole of the morphotectonic evidence and the azimuthal distribution analysis of each stream order, allowed to hypothesize that both the Fiume Fino and the Fiume Tavo have been affected by a significant differential movement having acted according to an important E-W tectonic line. The major uplift of the northern part – together with a more intense and widespread tectonization – should have caused a more vivid action of denudational processes for the Fiume Fino basin. Hypsometric analysis applied to the two main partial basins (Tavo and Fino) – and to the others into which the whole Fiume Saline basin has been subdivided as well – evidences a close relation between the pattern of hypsometric curves and the type and intensity of denudational processes.