Naturschutzgebiet Isla Glischa-Arvins-Seglias: A Protected Floodplain Landscape in Graubünden

The history of Isla Glischa-Arvins-Seglias is closely tied to the long human effort to manage and modify the Inn River in the Upper Engadin. Local communities began constructing flood protection dams along the Inn and its tributaries as early as the 18th and 19th centuries. The first lateral embankments along the Flaz were built in 1875.

Despite these efforts, periodic flood events continued to cause substantial damage. A particularly severe flood in 1954 prompted major new engineering works. In response, the Inn near Bever was converted into a narrow, straightened canal confined by high embankments, and tributary streams were heavily channelized. While these measures reduced flood risk and expanded agricultural land, they also cut the river off from its natural floodplain. Internal drainage canals dried out much of the former wetland, and the hardened riverbed offered poor habitat for fish and other aquatic species.

In 1992, recognizing the ecological importance of the remaining river landscape, Swiss authorities listed the area as a floodplain of national importance, creating the legal foundation for its modern protection. This designation placed the reserve within the Federal Inventory of Floodplains of National Importance and set the stage for future restoration.

Beginning in 2013, a long-term revitalization project has been reshaping the area. Working in multiple construction phases, project partners have been widening the river corridor, reintroducing natural dynamics, removing unnecessary embankments, and relocating key infrastructure to allow the river to spread again across the floodplain. The final phase near La Punt involves moving the cantonal road away from the river over a distance of more than two kilometers, freeing the Arvins area for natural river processes.

The landscape of Isla Glischa-Arvins-Seglias is shaped by the broad, relatively flat floor of the Upper Engadin, where the Inn flows with only a modest gradient of about 15 meters across the reserve. This gentle slope, combined with the valley's glacial history, produced a wide alluvial zone of gravel, sand, and silt that once supported extensive floodplain ecosystems.

Today, the reserve still preserves key features of this classic alpine riverine landscape. Gravel banks, shifting islands, and abandoned channels line the Inn, while side streams such as the Flaz, Ova Chamuera, and Beverin contribute sediment and hydrological variety. The Flaz, which once entered the Inn upstream of Samedan, was redirected through a new near-natural riverbed between 2002 and 2005, and now joins the Inn at 'Gravatscha'.

A distinctive feature of the landscape is the lake Lej da Gravatscha, which formed in a former riverbed where gravel was once extracted. The lake and the surrounding 'gravatscha' gravel area are emblematic of how past human activity has been integrated into a new natural setting. Other landscape elements include the marshes of Palüds-Agnas near Bever, the 14-hectare peatland at Surent Pascul, and the expansive open area around Arvins that is being restored to a more dynamic floodplain. The reserve also contains small ponds, riparian woodlands, wet meadows, and a network of old drainage canals that mark the area's agricultural history.

Two local road bridges near Bever cross the Inn within the reserve, while the main road and the Rhaetian Railway cross the floodplain near La Punt-Chamues-ch. As revitalization progresses, these infrastructural elements are increasingly being adapted or relocated to give the river more space.

The nature of Isla Glischa-Arvins-Seglias is defined by inland floodplain ecosystems typical of high-elevation alpine valleys. The reserve protects a mosaic of aquatic, wetland, riparian, and meadow habitats that reflect the transitional character of the Inn floodplain between aquatic and terrestrial environments.

Core ecological features include the open water and gravel shoreline habitats of the Inn and Lej da Gravatscha, the riparian willow and alder forests along the riverbanks, and the marshy and peat-forming wetlands that occupy low-lying parts of the valley floor. The 14-hectare peatland at Surent Pascul and the amphibian breeding area of Palüds-Agnas near Bever are integral parts of this ecological mosaic. The name 'Palüds' itself comes from the Romansh word for marsh, pointing to the area's long wetland heritage.

The floodplain acts as a critical transition zone between the alpine river system and surrounding dry valley habitats. Periodic flooding, sediment deposition, and groundwater seepage sustain a high diversity of microhabitats. Riverbank gravels provide nesting and feeding areas for specialized bird species, while the slower-moving side channels and ponds offer refuge for amphibians, invertebrates, and fish, especially as revitalization improves habitat connectivity.

The reserve represents an important example of how, even in a strongly engineered valley, restoring the river's natural dynamics can rapidly rebuild ecological complexity. The combination of flowing water, still water, wet meadows, and riparian woodland gives Isla Glischa-Arvins-Seglias high biodiversity value relative to its modest size.

Wildlife in Isla Glischa-Arvins-Seglias reflects the diversity of habitats that the floodplain offers: open river channels, gravel bars, ponds, marshes, peatlands, riparian forest, and meadows. The Inn and its side waters, particularly around Lej da Gravatscha, are important habitats for waterbirds that use the open water and shoreline for feeding and resting during both breeding and migration seasons.

The marshes near Bever, particularly the Palüds-Agnas area, are nationally recognized as an important amphibian breeding site. These wetlands provide critical spawning habitat for frogs and other amphibians that depend on shallow, seasonal water bodies. As revitalization reintroduces more dynamic flooding and creates new pools and side channels, amphibian populations are expected to benefit alongside other wetland fauna.

Fish life in the Inn has historically been constrained by channelization and hardened riverbeds. The revitalization project has substantially improved aquatic habitat structure, providing fish with more varied flow conditions, shelter, and spawning areas. Invertebrate communities along gravel banks and side channels also make up an important part of the reserve's fauna, supporting the wider food web that includes birds and amphibians.

Riparian woodland and meadow habitats host typical Engadin bird and small mammal species adapted to seasonally flooded environments, while the peatland at Surent Pascul supports species associated with moist, nutrient-poor ground conditions. Although the reserve does not host the large charismatic mammals more typical of mountain wilderness areas, its ecological richness lies in the diversity of smaller, often overlooked species that depend on dynamic floodplain processes.

Isla Glischa-Arvins-Seglias holds an important place in Swiss floodplain conservation. Designated in 1992, it is part of the Federal Inventory of Floodplains of National Importance, a federal instrument that recognizes floodplain sites of significant ecological value and subjects them to national protection standards.

The reserve's conservation value lies in its combination of rare and threatened habitat types, including alpine river floodplains, riparian forests, gravel lakes, peatlands, and amphibian breeding sites. The presence of a nationally important amphibian spawning area at Palüds-Agnas and the 14-hectare peatland at Surent Pascul underlines the reserve's role in protecting species and habitats that are otherwise scarce in the highly developed Upper Engadin.

The long-running revitalization program is central to the reserve's conservation significance. Past flood-control engineering, especially after the 1954 flood, had reduced the river to a narrow channel and drained surrounding wetlands, fragmenting ecological processes. The restoration project launched in 2013 aims to reverse this by widening the river corridor, reactivating floodplain dynamics, reconnecting side channels, and allowing the river to create new habitats naturally.

Beyond ecological restoration, the project also reconnects flood protection with habitat creation, demonstrating how flood retention areas can serve both human safety and biodiversity goals. The reserve thus serves as a model for integrating river engineering, land use, and ecological recovery in a densely settled alpine valley.

The cultural dimension of Isla Glischa-Arvins-Seglias is rooted in the Romansh-speaking heritage of the Upper Engadin. The reserve's name itself is drawn from local place names that reflect long familiarity with the river landscape: 'Isla Glischa' refers to flat, island-like areas near the river, while 'Arvins' and 'Seglias' are historic land parcels at the northern end of the floodplain. Romansh words such as 'isla' (island), 'glischa' (flat, slippery), 'palüd' (marsh), and 'grava' (gravel, alluvial material) are preserved in local place names and offer a vivid linguistic record of the valley's natural character.

The floodplain has long been part of the Engadin's agricultural and settlement landscape. Communities have shaped the river for centuries through flood-control works, drainage of wetlands for pasture and crop cultivation, and gravel extraction for construction. Some of these interventions, such as the gravel pit that later became Lej da Gravatscha, have become integral features of today's reserve.

The area also plays a seasonal cultural role. In winter, cross-country ski trails run through the floodplain, including the route of the famous Engadin Skimarathon, which crosses the reserve near Gravatscha every March. This connection between a nationally important ecological site and a major regional cultural event underscores how deeply the Inn floodplain is woven into the identity and daily life of the Upper Engadin.

Isla Glischa-Arvins-Seglias stands out for combining nationally protected floodplain status with one of the most ambitious river restoration programs in the Swiss Alps. Its scale within the Upper Engadin, its link to the Inn and its key tributaries, and its rich mosaic of gravel lakes, riparian forest, peatland, and marsh habitats give it a distinctive ecological profile.

Key highlights include the gravel lake Lej da Gravatscha, the nationally important amphibian breeding area at Palüds-Agnas, the peatland at Surent Pascul, and the expansive, increasingly dynamic floodplain near Arvins. The ongoing revitalization works, including the planned relocation of several kilometers of cantonal road near La Punt, make the reserve a living laboratory for floodplain restoration in an alpine setting.

Isla Glischa-Arvins-Seglias is best experienced during the warmer months, when the dynamic character of the floodplain is most visible. Late spring and summer bring active river flows, lush riparian vegetation, and the peak breeding and feeding activity of waterbirds and amphibians in the ponds and marshes. These seasons also offer the best conditions for observing ongoing restoration work and the evolving river channels.

Winter gives the reserve a very different character. A cross-country ski trail runs through parts of the floodplain, including the route of the Engadin Skimarathon in March, when the wide, open valley floor becomes a major venue for a regional sporting and cultural event. Visitors interested in wetland ecology, riparian forest, or floodplain dynamics will find the most rewarding experience between late spring and early autumn.