Vanelli et al. (2026) An analysis of flood risk changes over time through a paired events approach in Southern Brazil

Identification

• Journal: Climate Risk Management
• Year: 2026
• Date: 2026-09-10
• Authors: Franciele Maria Vanelli, Leonardo Romero Monteiro, Masato Kobiyama, Mariana Madruga de Brito
• DOI: 10.1016/j.crm.2026.100883

Research Groups

• Institute of Hydraulic Research, Federal University of Rio Grande do Sul, Brazil
• State University of Santa Catarina, Brazil
• Department of Urban and Environmental Sociology, Helmholtz Centre for Environmental Research, Germany
• Institute of Geography, Leipzig University, Germany

Short Summary

This study investigates flood risk dynamics in Rio Negrinho, Southern Brazil, from 1980 to 2024 using a paired event analysis and mixed methods. It reveals that adaptation strategies, particularly critical infrastructure relocation and non-structural measures, effectively reduce flood risk, though implementation is complex and influenced by socio-political factors.

Objective

• To investigate the drivers that shape flood risk over time in Rio Negrinho Municipality, Southern Brazil, between 1980 and 2024.
• To understand how physical (hazards) and social components (exposure, vulnerability, and capacity) interact to shape flood risk over time, particularly in a data-scarce Global South context.

Study Configuration

• Spatial Scale: Negrinho River watershed (approximately 305 km²) for hydrological processes, and the urban area of Rio Negrinho Municipality for social processes.
• Temporal Scale: 1980 to 2024 (44 years), focusing on five major flood events (1983, 1992, 2010, 2014, 2023) and four paired event comparisons.

Methodology and Data

• Models used: Not applicable; the study employed an empirical data-driven analysis using a mixed-methods approach (convergent parallel design) rather than hydrological or climate models for simulations.
• Data sources:
  • Official documents: Brazilian Atlas of Natural Disasters (1991–2012), Digital Atlas of Disasters in Brazil (1991–2023), Brazilian Integrated Disaster Information System (S2iD) records (2003–2024), State of Emergency and Public Calamity reports.
  • Hydrological and meteorological data: Monitoring stations for rainfall (mm) and water level (m) at the Negro River.
  • Census data: Brazilian Institute of Geography and Statistics (IBGE) for 1980, 1991, 2010, and 2022, providing population size and socioeconomic vulnerability indicators (gender, age, income, education).
  • Grey literature: Scientific studies, local reports, and newspapers.
  • Stakeholder knowledge: Focus group discussions (18 participants), six field trips, and informal conversations with local residents.
  • Field data: Used for estimating maximum flooded area.
  • Official municipal documents: Rio Negrinho City Hall website (e.g., Master Plan, Contingency Plan, Macrodrainage Plan, Mobility Plan).

Main Results

• Both severe (1983, 1992, 2014) and nuisance floods triggered changes in risk management practices and adaptation responses in Rio Negrinho.
• Socio-political factors, including social articulation, political decisions, and available financial resources, significantly influenced the implementation of adaptation measures.
• Relocation of critical infrastructure (City Hall, Municipal Hospital, Fire Department) away from flood-prone areas, primarily after the 1983 and 1992 floods, minimized cascading effects during subsequent events.
• Implementation of non-structural measures, such as the Municipal Civil Protection and Defense Contingency Plan (2017, revised 2021), establishment of a Civil Protection and Defense System (2018), and installation of a river monitoring camera (2022), improved preparedness and adaptive capacity.
• Socioeconomic vulnerability, assessed using a composite index (gender, age, income, education), showed limited variation (0.22–0.27) between 1980 and 2024, indicating no drastic changes in this aspect.
• Despite planning efforts, proposed structural measures (levees, dams) were not implemented due to concerns over environmental impacts, high costs, and maintenance.
• The 2023 flood, characterized by sequential events lasting over a month, highlighted the urgency of improving mobility strategies and caused significant indirect economic losses to shopkeepers, which were not systematically recorded in official documents.

Contributions

• Provides the first long-term (1980–2024) analysis of changing flood risk dynamics in a Global South case study, specifically Rio Negrinho, Brazil.
• Demonstrates the effectiveness of a mixed-method, socio-hydrological approach in understanding local responses to flood events in data-scarce environments.
• Integrates diverse evidence sources, including co-produced knowledge with local stakeholders, to reconstruct past events and analyze risk dynamics where conventional data-intensive methods are often unfeasible.
• Highlights the context-specific nature of flood risk and the crucial role of socio-political aspects in driving or hindering the implementation of adaptation measures.
• Calls for dynamic assessments of vulnerability and exposure, and systemic monitoring of risk reduction and adaptation measures in the Global South to improve understanding of complex risk trajectories.

Funding

• Brazilian National Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq) [grant number: 141384/2019–0]
• Volkswagen Foundation, through the CASCADE Grant (partial funding for Mariana Madruga de Brito)
• Helmholtz Centre for Environmental Research – UFZ (for article processing charges)

Citation

@article{Vanelli2026analysis,
  author = {Vanelli, Franciele Maria and Monteiro, Leonardo Romero and Kobiyama, Masato and Brito, Mariana Madruga de},
  title = {An analysis of flood risk changes over time through a paired events approach in Southern Brazil},
  journal = {Climate Risk Management},
  year = {2026},
  doi = {10.1016/j.crm.2026.100883},
  url = {https://doi.org/10.1016/j.crm.2026.100883}
}