Building permit for a riverbank protection and leisure facility on the Aare: remittal due to unresolved riverbank vegetation and lack of balancing of interests in the water space

Facts

The building authority of the City of Olten submitted to the Department of Construction and Justice of the Canton of Solothurn (BJD) the application for a riverbank protection and leisure facility on the left bank of the Aare between the Gäubahn bridge and the Strandbad. The dilapidated riverbank wall is to be renovated and the leisure use of the Aare bank upgraded.

The complainant [A.] , owner of the adjoining parcel No. 1933, lodged an objection and requested refusal of the permit for the three new southern steps and the seating steps above the riverbank wall. The BJD and the cantonal Department of Economic Affairs dismissed the objection on 3 December 2020 and granted the permit for construction outside the building zone, the fisheries permit, the water protection permit and the clearing permit for the riverbank vegetation. The Construction Commission of the City of Olten dismissed the objection on 6 January 2021 and granted the building permit subject to conditions and requirements.

The Administrative Court of the Canton of Solothurn dismissed the appeal on 20 September 2021. The complainant lodged a public law appeal with the Federal Supreme Court on 29 October 2021 and requested annulment and remittal to the Administrative Court. The Federal Office for the Environment (BAFU) found that the decision was only partially compatible with federal environmental law. The Federal Supreme Court dismissed the application for suspensive effect on 22 December 2021.

The subject matter of the dispute is solely the new seating options (seating plinth of the riverbank wall and stone blocks) and the three new steps in the upper section of approx. 65 m; the bank protection, the inlet and outlet point and the facilities for the Olten Pontoon Sports Club (PSVO) are not disputed.

Considerations

The public law appeal is admissible against the final cantonal decision of the last instance (Art. 82 lit. a, 86 para. 1 lit. d, 90 FSCA); the complainant is entitled to appeal as a neighbour (Art. 89 para. 1 FSCA). The Federal Supreme Court examines the violation of federal law (Art. 95 lit. a FSCA); complaints of violation of fundamental rights are only examined insofar as they are substantiated (Art. 106 para. 2 FSCA).

On the question of watercourse engineering under Art. 37 WPA: Selective measures for structures on watercourses that serve other purposes, such as landing stages, do not fall under the concept of engineering works. The steps are therefore not watercourse engineering within the meaning of Art. 37 WPA, and Art. 4 para. 2 WBG does not apply. The seating plinth and stone blocks have a dual function: they also serve erosion protection, but their specific design serves the leisure facility. The seating plinth, the seating rows and the steps prevent site-appropriate riverbank vegetation and promote leisure use, which may run counter to the objective of Art. 37 para. 2 WPA; it must therefore be examined whether the leisure facility is permissible within the water space.

On the permit within the water space under Art. 41c para. 1 WPO: The facilities undisputedly lie within the 20 m wide water space of the Aare. Site dependence requires that the facility cannot, due to its purpose or local conditions, be built outside the water space. The purpose of enabling people to linger and swim directly on the Aare does in principle make the facility site-dependent. However, this cannot mean that such facilities may be erected anywhere within the water space; an objective need regarding location, scope and design is required, which in principle presupposes the examination of alternative sites. The contested decision lacks such considerations. It appears sensible, however, to improve access at sections already hard-engineered and used for leisure purposes, which supports site dependence. Leisure use lies in the public interest, but a precise analysis of the public interests in the individual case is required. Flood protection is not impaired.

On the municipal riverbank protection zone (§ 24 ZR Olten): The zone aims to preserve and upgrade the banks and to ensure free access for those seeking recreation; buildings are not permitted, and facilities only if compatible with the purpose of the zone. The Administrative Court was entitled to regard the project as conforming to the zone; the complaint of arbitrary application of municipal law is not sufficiently substantiated. A planning obligation (entry in the structure plan) is not considered mandatory because of the relatively short, already built-up section, although further leisure projects on the Aare bank may need to be taken into account.

On the protection of riverbank vegetation under Art. 21 and 22 NCHA: Riverbank vegetation comprises natural or near-natural, site-appropriate plant communities in the fluctuation zone of the watercourse and the groundwater. The Administrative Court stated in general terms that this was not floodplain, without making findings on the type and frequency of the vegetation. An intervention in riverbank vegetation cannot be ruled out based on the file, as information on the shrub and herb layers is lacking. A clearing permit under Art. 22 para. 2 NCHA may only be granted for interventions permitted under water engineering and water protection legislation; Art. 41c para. 1 WPO does not fall into this category, as the ordinance-maker did not intend to introduce new exceptions to riverbank vegetation protection. Clearing for the leisure facility is therefore impermissible; planting site-appropriate shrubs does not change this.

On hedge protection: The riverbank shrubbery is…