Topology – Spring Semester 2026
Hours: 2 hrs, on Mondays 15:45-17:30
Room: LVML PC-room HIL H40.8
Lecturers: Philipp Urech
RESEARCH | The elective course is embedded in NewUrbES, part of the National Research Programme 82 on Biodiversity. The programme investigates how biodiversity can be strengthened in Swiss settlement areas and how spatial landscape aesthetics can be integrated into planning and design. Within this framework, NewUrbES explores how buildings and landscape connect though architectural elements such as ground, facades, walls and roofs that function as ecological interfaces rather than barriers. The project focuses on two case studies in the Zurich region—the Gaswerk-Areal in Schlieren and the housing cooperative in Friesenberg.
CHALLENGE | Urbanisation exerts significant pressure on biodiversity, particularly within the Critical Zone—the thin near-surface layer extending from vegetation canopy to freshwater aquifers. In Switzerland, densification policies promoted under the Federal Act on Spatial Planning aim to limit sprawl and protect open landscapes. While effective in containing outward expansion, this policy intensifies interventions within already urbanised soil systems.
Excavation, sealing, compaction, and artificial soil replacement reduce soil biodiversity at parcel and neighbourhood scale. Soil organisms including microbes, fungi, invertebrates, and roots, regulate nutrient cycles, water infiltration, and carbon storage. When construction disrupts their habitat, impacts cascade into hydrological, climatic, and ecological processes. The project therefore proposes a shift: built structures should operate as functional ecosystems, reducing biodiversity loss and reconnecting fragmented habitats.
Soil excavation | In many Swiss developments, construction begins with deep excavation to accommodate parking, storage, and shelters required under the Federal Act on Civil Protection and Civil Defence. Entire parcels are often cleared several metres below grade, removing the natural soil profile. This process eliminates the biologically active A horizon, rich in organic matter and microbial life. Even if topsoil is temporarily stored and reapplied, its structure and ecological networks are disrupted. Mycorrhizal systems are severed, aggregates collapse, and pore networks that sustain gas exchange disappear. In areas of shallow groundwater, protected under the Federal Act on the Protection of Waters, excavation may also require dewatering, altering soil moisture regimes and affecting adjacent vegetation. Excavation thus represents both material displacement and ecological discontinuity within the soil column.
Soil sealing | Soil sealing occurs when permeable ground is covered by impermeable materials such as concrete or asphalt. In compact environments like Zurich and its surrounding municipalities, sealing includes building footprints, underground slabs, roads, and paved courtyards. Sealing prevents infiltration, redirecting precipitation into drainage systems instead of allowing it to recharge soil and aquifers. Without organic inputs and natural moisture cycles, microbial activity declines and soil biodiversity diminishes. Landscaped areas above underground garages are often separated from natural ground by structural slabs, interrupting vertical ecological continuity. Over time, cumulative sealing fragments habitats and reduces ecosystem-service performance at neighbourhood scale.
Soil compaction | Mechanical compaction caused by heavy machinery compresses soil layers and collapses pore networks that store air and water. Compacted soils exhibit reduced permeability, limited root penetration, and lower oxygen availability. In clay-rich soils typical of parts of the Swiss Plateau, structural recovery may take decades. Even green spaces adjacent to buildings frequently rest on compacted subsoil, limiting their ecological function. Compaction therefore represents a hidden but persistent degradation mechanism, reducing soil resilience long after construction is completed.
Artificial soil replacement | Where excavation removes native ground, engineered substrates are commonly installed. On podium decks or above underground structures, shallow artificial soils support vegetation but rarely replicate the depth-dependent processes of natural soils. These systems are designed for structural stability and drainage rather than biological complexity. Artificial soils typically lack stratified horizons and long-term microbial communities. Their hydrology is controlled rather than emergent, and their ecological performance is limited. This substitution transforms soil from a living, evolving system into a technical layer within construction assemblies.
CASE STUDY SITES | Two selected sites illustrate contrasting but complementary conditions: post-industrial regeneration and cooperative residential densification. Both reveal how the architectural section—how buildings meet and occupy the ground—profoundly shapes the ecological future of the Critical Zone in Swiss cities.
The Gaswerk-Areal originated in 1897 as a major gas production facility supplying Zurich. Decommissioned in 1972, the site retains significant industrial architecture and has been adaptively reused for mixed functions. Located in a rapidly densifying municipality, it exemplifies post-industrial transformation. Industrial gas production historically contaminated soils, requiring remediation before redevelopment. The site therefore presents a dual challenge: addressing past pollution while avoiding new ecological degradation. It offers opportunities to explore partial unsealing, phytoremediation, and the re-establishment of continuous soil systems within a former industrial landscape.
The Siedlungs-Genossenschaft im Friesenberg was founded in 1924 and today comprises over two thousand cooperative housing units. The settlement is characterised by generous green spaces and a neighbourhood-oriented structure. Earlier construction phases maintained substantial permeable ground. More recent renovations and densification, however, have introduced additional underground infrastructure and sealed surfaces. The cooperative context provides a laboratory for negotiating biodiversity goals within lived residential environments. Questions of unsealing courtyards, reducing parking areas, and increasing soil depth intersect here with social, economic, and regulatory considerations.
Point cloud model showing the biophysical performance of the landscape near the Friesenberg area. The 3D model is overlayed with the wind simulation of the FITNAH Climate model (wind speed from 0 to 1.5 m/s) and segmented according to known breezeways (Kaltluftsystem, GeoZ).