TF, 08.10.2025, 1C_271/2024
Facts
A construction company was granted a permit to build four residential buildings on a plot of land adjacent to the Töss River in the municipality of Zell (ZH). The cantonal and municipal authorities issued the permit based on the transitional provisions of the Waters Protection Ordinance (WPO), which provide for a provisional water space of 20 meters on each side of the watercourse. The project complied with this distance.
WWF Switzerland appealed this decision, arguing that the definitive water space for the Töss, while not yet formally established, would be much wider (at least 90 meters according to existing cantonal expert reports) and that the construction project would encroach upon this area. The Administrative Court of the Canton of Zurich rejected the appeal, ruling that only the transitional provisions were applicable as long as the definitive space had not been formally delineated. The WWF took the case to the Federal Supreme Court.
Legal Analysis
The Federal Supreme Court reiterates that cantons were required to delineate the definitive water space for all watercourses by December 31, 2018 (Art. 36a of the Waters Protection Act [WPA], Art. 41a and 41b WPO, and the transitional provisions of the May 4, 2011 amendment to the WPO). This space is crucial for ensuring the natural functions of watercourses, flood protection, and revitalization.
For large watercourses like the Töss, the provisional water space is often significantly narrower than the required definitive space. The legislature tolerated this protection gap, but only for a limited period, specifically until the implementation deadline at the end of 2018.
When a canton fails to meet this deadline, it cannot authorize construction projects that risk compromising future, legally required planning. To secure this planning, authorities have the instrument of a planning zone at their disposal (Art. 27 of the Spatial Planning Act [SPA]). Although its enactment is in principle optional, it can become an obligation if future planning is at risk of being jeopardized.
Application to the Case
The Federal Supreme Court finds that the construction project, while compliant with the provisional water space, would clearly be located within the definitive space of at least 90 meters that must be established for the Töss based on existing expert reports. The construction of these buildings would therefore prejudice the future delineation of this area and make any potential revitalization of the watercourse impossible (consideration 3).
Since the Canton of Zurich failed to meet the end-of-2018 deadline for establishing the definitive water space, it cannot rely on its own inaction to authorize a project that contravenes the objectives of federal law. The transitional provisions cannot be interpreted as an exhaustive rule that excludes any other protective measures after the deadline has expired.
Faced with the risk of compromising planning of major public interest that is required by federal law, the canton had an obligation to adopt a protective measure, in this case, a planning zone under Art. 27 SPA. In the absence of such a measure, the building permit could not be issued. The weighing of interests clearly tips in favor of protecting the watercourse—a paramount public interest—over the private interest in building, especially since the zoning plan dated back to 1994 and environmental law has evolved significantly since then (consideration 4).
Outcome
The Federal Supreme Court upholds the appeal by WWF Switzerland. It annuls the judgment of the Zurich Administrative Court and, consequently, the building permit and the related cantonal authorizations. The case is remanded to the Department of Public Works of the Canton of Zurich for further proceedings, in particular to take the necessary planning measures.
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