Modellering af det terrænnære grundvand i Aabenraa

Climate change is expected to significantly affect shallow groundwater conditions in coastal urban areas, with potential consequences for flooding, infrastructure, and contaminant transport.
This study presents groundwater modelling of Aabenraa, Denmark, undertaken by Region of Southern Denmark and GEUS to assess the effects of climate change and selected climate adaptation measures on shallow groundwater levels and contaminant migration.
The modelling considers changes in sea level and precipitation, as well as sewer rehabilitation, groundwater drainage, and nature restoration involving the removal of artificial drainage.
The results indicate that future changes in shallow groundwater levels in Aabenraa will be driven primarily by sea-level rise, with a modelled increase of up to 65 cm, whereas changes associated with precipitation are generally limited to approximately 10 cm.
The influence of sea-level rise extends several hundred metres inland, with groundwater-level increases of up to approximately 30 cm occurring 250–1,000 m from the harbour/coast in parts of the study area.
These findings demonstrate that sea-level rise is a key factor when assessing future shallow groundwater conditions in coastal cities.
Sewer relining may substantially alter groundwater levels, typically by 10–30 cm and locally by more than 50 cm.
Groundwater drains provide an effective means of lowering groundwater levels, although their influence may extend beyond the drainage area depending on geological conditions and hydraulic barriers.
Conversely, removal of artificial drainage as part of nature restoration can cause substantial groundwater-level increases both within and beyond the restored area.
Particle tracking demonstrates that adaptation measures can alter groundwater flow paths and consequently redirect contaminant plumes towards areas not previously considered at risk.
Notably, sewer relining can significantly affect contaminant-plume trajectories despite relatively limited changes in groundwater-table elevation.
In contrast, groundwater drainage may produce substantial groundwater-level changes while causing comparatively limited changes in simulated particle trajectories.
Overall, the results indicate that both climate change and urban adaptation measures can substantially modify contaminant transport and therefore influence future risk assessments of contaminated sites.
The findings highlight the importance of integrating groundwater management, climate adaptation, and contaminant risk assessment in the planning of climate-resilient coastal urban areas.