Medium-term fluvial island evolution in a disturbed gravel-bed river (Piave River, Northeastern Italian Alps)

River islands are defined as discrete areas of woodland vegetation surrounded by either water-filled channels or exposed gravel. They exhibit some stability and are not submerged during bank-full flows. The aim of the study is to analyze the dynamics of established, building, and pioneer islands in a 30-km-long reach of the gravel-bed Piave River, which has suffered from intense and multiple human impacts. Plan-form changes of river features since 1960 were analyzed using aerial photographs, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces, and maximum and mean height of their vegetation. The results suggest that established islands lie at a higher elevation than building and pioneer islands, and have a thicker layer of fine sediments deposited on their surface after big floods. After the exceptional flood in 1966 (RI>200 years) there was a moderate increase in island numbers and extension, followed by a further increase from 1991, due to a succession of flood events in 1993 and 2002 with RI>10 years, as well as a change in the human management relating to the control of gravel-mining activities. The narrowing trend (1960-1999) of the morphological plan form certainly enhanced the chance of islands becoming established and this explains the reduction of the active channel, the increase in established islands and reduction of pioneer islands

The Tagliamento River: a model ecosystem of European importance

In NE Italy is a remarkable floodplain river that retains the dynamic nature and morphological complexity that must have characterized most Alpine rivers in the pristine stage. This river system, the Fiume Tagliamento, constitutes an invaluable resource not only as a reference site for the Alps, but as a model ecosystem for large European rivers. The Tagliamento has a number of attributes that have not been given due consideration in river ecology: (i) an immense corridor of more than 150 km2 that connects the land and the sea and two biomes, the Alps and the Mediterranean; (ii) unconstrained floodplain segments characterised by a dynamic mosaic of aquatic/terrestrial habitats; and (iii) a large number of vegetated islands (ca. 700). We believe it is critical to understand the functional roles of these endangered attributes in order to effectively engage in river conservation and management programmes. The Tagliamento River in Italy offers the rare opportunity to investigate natural processes at a scale that can be studied almost nowhere else in Europe

Roads, Railroads, and Floodplain Fragmentation Due to Transportation Infrastructure Along Rivers

River floodplains comprise about 7 percent of the land area of the United States and are areas of great biodiversity and ecological productivity, much of which is due to the many connections between terrestrial and aquatic systems in these settings. The flat topography of floodplains, however, means that they are also ideal sites for transportation infrastructure that can disconnect the river from the surrounding landscape. Few studies have examined the role of roads and railroads as components of river system structure and function at landscape scales. In this study, we use geographic information systems (GIS) and easily obtainable data to map the extent of floodplain disconnection caused by transportation infrastructure across two river basins in Washington State. Digital geologic or soils data, along with digital elevation data, provide the extent of total floodplain area, and transportation data define the extent of disconnection. Our results show that 44 percent to 58 percent of the total floodplain area in the three study basins is disconnected by these roads and railroads. Transportation infrastructure disconnected between 17 percent and 64 percent of the floodplain area in the individual study reaches. Federal Emergency Management Agency floodplain data often show where floodplains are truncated by infrastructure, particularly by large features or in urban areas, but do not capture the loss of total floodplain area. Relatively simple broad-scale documentation of infrastructure and floodplain disconnection has potential for guiding further study of floodplain fragmentation at multiple scales, providing an impetus for improving infrastructure design and repair and helping inform aquatic and floodplain management activities