Author(s): Luca Zanoni; Walter Bertoldi; Roberto Socin; Marco Tubino; Francesco Baruffi
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Keywords: River morphodynamics; Ecohydraulics; Remote sensing; Tagliamento River (Italy); Braided rivers; Field monitoring
Abstract: In this work we report on a field monitoring activity we are carrying out on a braided reach of the Tagliamento River, North East Italy. In order to capture the relevant morphological evolution of a braided network, a high detail of survey is required, because of the cascade of spatial and temporal scales that characterise their dynamics. We present a monitoring technique consisting in a ground-based photographic survey, where a picture is automatically acquired every one hour. The images are then rectified and processed with a semi-automatic procedure, that allowed a rapid and efficient analysis of the planimetric configuration. Such a system is able to monitor the evolution during a flood event, highlighting how and when the river moves. The preliminary results are reported on the inundation dynamics of a reach about 2 km long. A series of morphological parameters (e. g. inundated area, braiding index, network connectivity) have been analysed, that have been found to be relevant to describe the ecological status of a braided river. The investigation shows that the floodplain is characterised by a braided pattern for the whole monitored range of discharges: the braiding index keeps on the average always higher than 2 and the inundated area is less than the 30% of the total for the major part of the year. Finally, we present a comparison with a simple numerical model, that considers the local uniform flow for the surveyed cross-sections. The good agreement of the numerical results with the photographic survey suggests the possibility to use such a model to predict the behaviour at different flow stages or when a detailed planimetric monitoring is not available.
Year: 2007