Storm water management in Växjö - the Linnaeus canal and Växjö lake lagoons, Sweden

Historically, annual floods around Linnegatan flooded streets for days and filled building cellars, causing high cleaning/reconstruction costs. In the early 2000s, design targeted resilience to 10-year rainfall events, framed around recurrent heavy rain rather than climate change. Since the canal's construction, climate projections (SMHI) now indicate more frequent and roughly 10% more intense extreme precipitation, and the already-built city limits how far storm-water facilities can be retrofitted, unlike new development areas where climate change is planned for from the outset.

Prevent frequent flooding of Linnegatan, manage storm water and reduce future flood risk while buying time for further interventions; recognised in Vaxjo's 2013 climate adaptation strategy alongside a planned storm-water investment plan.

The historic above-ground stream under Linnegatan, which had been built over, was reopened by the late 1990s as the 220 m long Linnaeus canal, functioning as a storm-water storage tank that retains and slowly discharges water via an underground pipeline and sedimentation lagoons before it reaches Vaxjo Lake, reducing pollutant loads (nutrients, particles, heavy metals) to the lake.

Total investment cost was nearly 2,000,000 EUR, about 15% funded by the Swedish Government (Local Investment Program for Sustainable Development), the rest by the City of Vaxjo's Technical Department. The canal is dimensioned for a 10-year rainfall event; since construction, floods have occurred but have been less severe and less frequent than before. A co-benefit has been improved traffic safety (the canal reduced the street from four to two traffic lanes, with bridges as pedestrian crossing points), plus reduced pollutant flow to the lake and an aesthetic/historic streetscape value. Similar retention measures (e.g., ponds under a football field and a car park) have since been implemented elsewhere in Vaxjo.

Success came from combining storm-water management with pollutant control and co-benefits (traffic safety, urban landscape). Space constraints of the existing built environment meant the canal could only partially address future climatic conditions, serving as a partial/short-term solution while new-development areas plan explicitly for future climate.