Azadgar et al. (2026) Flood-sensitive land take (FSL) analysis: A new way to read how urban sealing shapes flood risk

Identification

• Journal: Journal of Environmental Management
• Year: 2026
• Date: 2026-04-01
• Authors: Anahita Azadgar, Andrea Benedini, Stefano Salata, Peter Lacoere, Joanna Badach, Lucyna Nyka
• DOI: 10.1016/j.jenvman.2026.129513

Research Groups

• Department of Urban Architecture and Waterscapes, Faculty of Architecture, Gda´nsk University of Technology, Gda´nsk, Poland
• Department of Architecture and Urban Planning, Politecnico di Milano, Italy
• KU Leuven, Faculty of Architecture, Ghent, Belgium

Short Summary

This study investigates how land take and land-use transitions influence urban flood risk by analyzing water accumulation in four European cities (Gda´nsk, Milan, Oslo, Ghent) between 2012 and 2018. It introduces the Water Accumulation Sensitivity Index (WASI) and Normalised Water Accumulation Sensitivity Index (NWASI) to quantify and compare hydrological impacts, revealing that land take typology significantly shapes flood sensitivity, with green infrastructure mitigating impacts while industrial and transport conversions amplify them.

Objective

• To analyze how land take and land use transitions vary across study areas and identify which transitions most influence flood risk.
• To develop novel quantitative indicators (WASI and NWASI) to capture and compare the hydrological impacts of urbanisation across diverse city contexts.
• To derive lessons for sustainable land management and flood risk mitigation policies in rapidly developing urban landscapes.

Study Configuration

• Spatial Scale: Four European cities: Gda´nsk (Poland), Milan (Italy), Oslo (Norway), and Ghent (Belgium). Data with a minimum mapping unit of 0.25 hectares.
• Temporal Scale: Land use changes and water accumulation analysis for the period between 2012 and 2018.

Methodology and Data

• Models used: InVEST Urban Stormwater Retention Model (Stanford University). Geographic Information System (GIS) techniques for Land Use Change (LUC) analysis.
• Data sources: Urban Atlas land use and land cover maps (2012, 2018). HYSOGs250m hydrologic soil groups. Mean annual precipitation derived from ERA5 in Google Earth Engine. Road centrelines extracted from OpenStreetMap.

Main Results

• Land take patterns varied significantly across the cities (2012–2018): Gda´nsk experienced extensive expansion (e.g., 141 hectares of pastures, 82 hectares of arable land converted), Milan had a modest increase (approximately 180 hectares), Oslo showed minimal land take but significant conversions of forest and agricultural land (approximately 30 hectares each), and Ghent uniquely directed a large share of land take towards urban green spaces.
• Water accumulation responses to land take varied: Gda´nsk and Milan showed increased accumulated water linked to conventional residential and industrial expansion. Oslo displayed high hydrological sensitivity despite minimal land take, due to forest and agricultural conversions. Ghent demonstrated that land take directed toward green infrastructure can stabilize or even reduce water accumulation.
• The Water Accumulation Sensitivity Index (WASI) and Normalised Water Accumulation Sensitivity Index (NWASI) quantify the marginal change in modelled water accumulation per unit area of land take.
• Hydrological sensitivity is strongly influenced by land take typology:
  • Conversions into industrial, commercial, and transport-related land uses consistently exhibit the highest WASI and NWASI values, reflecting high imperviousness (e.g., Milan showed 0.72–0.80 cubic meters per square meter for transitions into mine, dump, and construction sites; Oslo showed up to approximately 0.79 cubic meters per square meter for forest and agricultural conversions).
  • Land take directed toward urban green space (e.g., Ghent's new parks) resulted in negative WASI values, indicating improved infiltration and reduced water accumulation.

Contributions

• Introduces a novel analytical framework, Flood Sensitive Land Take (FSL), that directly links land take and flood risk by quantifying how specific land use transitions generate additional water accumulation.
• Develops and applies two new quantitative indicators, the Water Accumulation Sensitivity Index (WASI) and the Normalised Water Accumulation Sensitivity Index (NWASI), which enable spatially explicit and comparable assessments of urban flood sensitivity across diverse urban contexts and land use transitions.
• Provides evidence-based insights for urban policy and land take governance, supporting a shift from rigid zoning to performance-based standards and targeted mitigation strategies based on land take typology and spatial configuration.
• Demonstrates the operationalisation of flood-sensitive spatial planning using harmonised, publicly available European datasets, ensuring transparency, reproducibility, and adaptability for other urban settings.

Funding

Not explicitly stated in the provided text.

Citation

@article{Azadgar2026Floodsensitive,
  author = {Azadgar, Anahita and Benedini, Andrea and Salata, Stefano and Lacoere, Peter and Badach, Joanna and Nyka, Lucyna},
  title = {Flood-sensitive land take (FSL) analysis: A new way to read how urban sealing shapes flood risk},
  journal = {Journal of Environmental Management},
  year = {2026},
  doi = {10.1016/j.jenvman.2026.129513},
  url = {https://doi.org/10.1016/j.jenvman.2026.129513}
}