Restoring a glacier‐fed river: Past and present morphodynamics of a degraded channel in the Italian Alps

Scorpio, Vittoria; Andreoli, Andrea; Zaramella, Mattia; Moritsch, Sara; Theule, Joshua; Dell'Agnese, Andrea; Muhar, Susanne; Borga, Marco; Bertoldi, Walter; Comiti, Francesco

doi:10.1002/esp.4931

Cited by 19 publications

(27 citation statements)

References 75 publications

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“…The systematic recording of natural hazards in South Tyrol started in 1998 and has been maintained by the Autonomous Province of Bozen (see also Marchi et al, 2019; Schlögel et al, 2020; Scorpio et al, 2020). The available data indicates that the most common processes in the Sulden catchment are debris flows and debris floods, together with different types of small‐ to medium‐sized landslides (Figure 1d).…”

Section: Methodsmentioning

confidence: 99%

Pronounced increase in slope instability linked to global warming: A case study from the eastern European Alps

Savi

Comiti

Strecker

2021

Earth Surf Processes Landf

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In recent decades, slope instability in high‐mountain regions has often been linked to increase in temperature and the associated permafrost degradation and/or the increase in frequency/intensity of rainstorm events. In this context we analyzed the spatiotemporal evolution and potential controlling mechanisms of small‐ to medium‐sized mass movements in a high‐elevation catchment of the Italian Alps (Sulden/Solda basin). We found that slope‐failure events (mostly in the form of rockfalls) have increased since the 2000s, whereas the occurrence of debris flows has increased only since 2010. The current climate‐warming trend registered in the study area apparently increases the elevation of rockfall‐detachment areas by approximately 300 m, mostly controlled by the combined effects of frost‐cracking and permafrost thawing. In contrast, the occurrence of debris flows does not exhibit such an altitudinal shift, as it is primarily driven by extreme precipitation events exceeding the 75th percentile of the intensity‐duration rainfall distribution. Potential debris‐flow events in this environment may additionally be influenced by the accumulation of unconsolidated debris over time, which is then released during extreme rainfall events. Overall, there is evidence that the upper Sulden/Solda basin (above ca. 2500 m above sea level [a.s.l.]), and especially the areas in the proximity of glaciers, have experienced a significant decrease in slope stability since the 2000s, and that an increase in rockfalls and debris flows during spring and summer can be inferred. Our study thus confirms that “forward‐looking” hazard mapping should be undertaken in these increasingly frequented, high‐elevation areas of the Alps, as environmental change has elevated the overall hazard level in these regions.

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Section: Methodsmentioning

confidence: 99%

Pronounced increase in slope instability linked to global warming: A case study from the eastern European Alps

Savi

Comiti

Strecker

2021

Earth Surf Processes Landf

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“…At the same time, flood regulation with altered discharge and bedload trapping (by the Sylvenstein reservoir) reduce the erosivity and energy of floods. The resulting succession then leads to additional stabilization of banks and floodplains, so that after the removal of the embankment, the floodplains must first be recreated (Scorpio et al, 2020).…”

Section: Effectiveness Of Gravel Bar Restorationmentioning

confidence: 99%

“…Already today, floods in the lower reaches of regulated rivers are higher and reach their peak faster, causing more severe flooding downstream (Kiedrzy nska et al, 2015). As the frequency of such extreme events will increase with climate change, it becomes clear that a removal of dykes and the widening of active river corridors are urgently needed (see Scorpio et al, 2020).…”

Section: Implications For Biodiversity and Flood Controlmentioning

confidence: 99%

“…In river restoration, the questions arise whether, for example, an increase in gravel bars can persist in the long term or will be lost due to succession or erosion after a few years (Bauer, Harzer, Strobl, & Kollmann, 2018; Scorpio et al, 2020; Zerbe, Rohrmoser, Scorpio, & Comiti, 2019). Thus, hydromorphological indicators have to be selected that can be easily applied across large scales (González del Tánago, Gurnell, Belletti, & García de Jalón, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Spatio‐temporal patterns in degradation and restoration of gravel bars along Alpine rivers

Woellner

Wagner

Crabot

et al. 2022

River Research & Apps

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Braided reaches were common along near‐natural Alpine rivers, and the associated habitat dynamics supported plant and animal species specialized on early‐successional stages. The extensive riparian zones could mitigate climate change by absorbing floods and by retaining water during droughts. Human impacts largely reduced active river corridors through altered discharge and construction of dykes, while recent restoration projects aim at increasing river dynamics. The causes and consequences of Alpine river degradation are well understood, but there are only few quantitative studies on floodplain degradation and restoration. Thus, we have reconstructed historical changes of gravel bars along five Alpine rivers (Iller, Inn, Isar, Lech, and Wertach) in Southern Germany in the period 1808–2009, based on historical maps and aerial images. We found losses of >90% in gravel bar area along these rivers since the mid‐19th century. The decline was caused by a reduction of the active river corridor and by ongoing succession of the remaining open habitats. Within the past 30 years, at the Isar River, restoration measures were realized with the aim to widen the active river corridor and to recreate gravel bars. In four restored reaches, we found that 5% of the historical gravel bar area recovered, and that the proportion of restored gravel bar area was highest after intermediate flooding. We conclude that the active river corridors of German Alpine rivers are almost completely lost, and that more extensive restoration needs to be done to preserve the habitat dynamics and biodiversity of these systems, and to adapt Alpine rivers to climate change.

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“…In recent years, several studies have been published on the interaction between fluvial processes and vegetation dynamics [e.g., "fluvial biogeomorphic succession concept" by Corenblit et al (2007Corenblit et al ( , 2015]. They primarily focus on braided river stretches in glacially unaffected catchments or further downstream of the glacier forelands (e.g., Gurnell et al, 2001;Egger et al, 2019;Scorpio et al, 2020). Against this background the present study focusses on two research questions involving longterm changes of high Alpine glacial fluvial systems:…”

Section: Introductionmentioning

confidence: 99%

Tracing the Long-Term Evolution of Land Cover in an Alpine Valley 1820–2015 in the Light of Climate, Glacier and Land Use Changes

Hohensinner

Atzler

Fischer

et al. 2021

Front. Environ. Sci.

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Alpine glacial environments and their fluvial systems are among those landscapes most comprehensively affected by climate change. Typically, studies on the consequences of climate change in such environments, e.g., glacier retreat, cover a maximum of 70 years, reflecting the availability of orthophotos or satellite images. This study addresses the long-term transformation processes in a glaciated catchment and highlights the role of human agency in a changing Alpine environment. In order to identify land cover changes between 1820 and 2015 in the Long-Term Ecosystem Research (LTER) site “Jamtal” (Tyrol, Austria) we apply a “regressive-iterative GIS reconstruction method” combining both historical maps and optical remote sensing data. Below 2,100 m a.s.l. the Jamtal experienced a massive 62% decline of unvegetated debris areas and bedrock outcrops (so-called “wasteland”) that was mainly transformed to grassland and sparsely wooded areas. Forests increased by an outstanding 323% and grassland was replaced by sparsely or densely wooded areas. This primarily reflects the abandonment of agricultural uses at unfavourable remote sites. In the higher (formerly) glaciated subbasin, ice-covered areas declined by 55%, which was associated with a major (82%) growth of exposed wasteland. Concurrently, Alpine grassland expanded by 196% and krumholz even by 304%. Approximately half of the new fluvial system that evolved in deglaciated areas between 1870 and 1921 still existed in 2015. Unconsolidated debris buried almost one fifth of the new channels, and almost one third was colonized by vegetation. Recent data show that the deglaciation process is much faster than the colonization process by Alpine vegetation. Accordingly, the extent of wasteland has expanded and potentially amplifies the sediment supply to the fluvial system. Alterations in high Alpine hydrological and sediment/debris regimes significantly affect human use in lower, more favourable areas of the Alpine region. The long-term investigation of the Alpine landscape reveals that the transformation processes have accelerated in recent decades.

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Restoring a glacier‐fed river: Past and present morphodynamics of a degraded channel in the Italian Alps

Cited by 19 publications

References 75 publications

Pronounced increase in slope instability linked to global warming: A case study from the eastern European Alps

Pronounced increase in slope instability linked to global warming: A case study from the eastern European Alps

Spatio‐temporal patterns in degradation and restoration of gravel bars along Alpine rivers

Tracing the Long-Term Evolution of Land Cover in an Alpine Valley 1820–2015 in the Light of Climate, Glacier and Land Use Changes

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