Facts

The Government of the Canton of Graubünden approved on 15 March 2016 the amendment of the regional structure plan of Surselva and the update of the cantonal structure plan concerning the Ruinaulta/Rheinschlucht natural monument. The amendments included the designation of a continuous footpath in the valley floor of the Rhine Gorge on the territory of the municipality of Trin, from the Isla Bella bridge to the Trin station of the Rhaetian Railway (RhB). The hiking trail lies within the BLN object No. 1902 'Ruinaulta'.

The voters of the municipality of Trin, in the context of a partial revision of local planning, enacted on 21 June 2016 the zoning and general development plan (ZP/GEP) 1:5'000 Ruinaulta. This changes the location and extent of the existing nature conservation zone and establishes a new path section from the Isla Bella bridge to the Pintrun hydroelectric plant (EW), between the railway line and the riverbank of the Vorderrhein, with a pedestrian tunnel parallel to the Ransun railway tunnel.

Pro Natura, Pro Natura Graubünden, Schweizer Vogelschutz SVS/BirdLife Schweiz and WWF Schweiz requested non-approval. The cantonal government approved the ZP/GEP on 8 August 2017 with conditions and dismissed the applications insofar as they were admissible. The associations lodged an appeal with the Administrative Court, which dismissed it by judgment of 3 October 2018. By partial revision of the Floodplain Ordinance (AuenV) of 29 September 2017, in force since 1 November 2017, the floodplain object No. 385 Ruinaulta was included. On 3 November 2017, the DETEC additionally approved the amendment of the cantonal structure plan within the framework of the 'Approval Package 2016'.

By public law appeal of 9 November 2018, Pro Natura, SVS and WWF Schweiz appealed to the Federal Supreme Court and requested the annulment of the administrative court judgment as well as of the ZP/GEP 1:5'000 Ruinaulta. The Federal Supreme Court upheld the appeal.

Considerations

The Federal Supreme Court notes that the disputed hiking trail affects not only a BLN area but also a floodplain of national significance. Inventory biotope areas of national significance are protected under Art. 18a NCHA by the ordinances of the Federal Council, in particular the AuenV, which is guided by the principle of undiminished preservation under Art. 6 NCHA. Deviations from the protection objective, in particular technical interventions, require, in addition to the direct site dependency, a predominant interest of national significance (Art. 4 para. 2 AuenV). The cantons must regulate the protection and maintenance of the objects (Art. 18a para. 2 NCHA, Art. 3 and 5 AuenV, Art. 17 SPA); land-use planning is a suitable instrument for detailed delimitation. The concept of floodplain is not legally defined, but floodplains are dynamic habitats of great importance for biodiversity.

The common sandpiper is a floodplain-typical bird species protected under Art. 7 HuntA, classified as endangered on the Red List and strictly protected under the Bern Convention, which occurs in the Emerald area CH09 Ruin'Aulta. On the national priority list of the FOEN it holds the highest level 1. Under Art. 5 para. 2 lit. c AuenV, the cantons must ensure that recreational uses in floodplain areas are compatible with the protection objective, and under Art. 7 para. 4 HuntA they must protect birds from disturbances.

In the detailed delimitation, the municipalities have a margin of assessment, which is however small. Along a railway line, delimitation according to the implementation aid is generally to be made up to the railway line; a deviating delimitation is only permissible for objective reasons. The flood argument of the appellants does not succeed, as the terrain does not lie in a flood zone. Railway law aspects (Art. 18, 19, 21 RailA, Art. 24 RailO), however, must be taken into account in the delimitation. An extensive maintenance zone up to 20 m from the track axis may, depending on the circumstances, belong to a habitat worthy of…