Assessing the planform changes of the Tammaro River (southern Italy) from 1870 to 1955 using a GIS-aided historical map analysis

摘要

Most part of the vast scientific literature dealing with channel adjustments focuses on the period between the second half of the twentieth century and nowadays, when most of the adjustments occurred and data availability is generally great. On the contrary, few studies were carried out on older adjustments, notwithstanding their analysis is fundamental to fully understand both more recent evolutionary trends and the role possibly played by human disturbances. The lack of studies on older adjustments is total for rivers located in southern Italy. The present study attempts to partly fill this gap. An analysis of the planform changes experienced by Tammaro R. between 1870 and 1955 was carried out by means of a detailed GIS-aided analysis of historical maps. The results were interpreted in the framework of the pre-existing geomorphological, geographical and socio-economic literature. This latter highlighted that the Tammaro R. basin in the studied period was scarcely inhabited and almost un-anthropized, especially in the first part of the studied period. Between 1870 and 1909, the river underwent a slight and quite inhomogeneous widening and moderate increase in fluvial bars, together with a slight straightening and shortening, but without substantial changes in channel morphology, which was single-thread. Between 1909 and 1955, the river experienced a homogeneous and marked widening, increase in sinuosity and lengthening, together with a strong increase in fluvial bars, and the channel morphology drastically changed from single-thread to transitional. This trend was opposite to that of most rivers in that period, possibly because of the scarce human impact on both the Tammaro R. and its basin.