Socio-Environmental Vulnerability And ExtremeHydrometeorological Events In Coastal Urban Settlements: Geotechnological Approaches For Climate Adaptation In Southern Brazil

Extreme hydrometeorological events have intensified dramatically in Southern Brazil, with the catastrophic floods of April-May 2024 representing the worst climate disaster in Rio Grande do Sul's history, affecting 478 municipalities (96% of the state), causing 183 deaths, and displacing over 580,000 people. This unprecedented event, combined with recurrent flooding episodes including the October 2015 event in Pelotas region, underscores the urgent need for integrated risk assessment frameworks and climate adaptation strategies in vulnerable coastal territories. This research investigates socio-environmental vulnerability and extreme event exposure in Pontal da Barra, a coastal settlement in Pelotas (RS), employing advanced geotechnologies and multi-criteria decision analysis to support evidence-based climate resilience policies. The study area represents a critical case of compounded vulnerability: informal settlements in Permanent Preservation Areas (APPs), wetland degradation, inadequate infrastructure, lowincome populations, and direct exposure to flooding, storm surges, and sea-level rise impacts. The methodological framework integrates: (i) high-precision geodetic surveys using GNSS-RTK and aerial photogrammetry via RPAS/drones at 60m altitude; (ii) extreme event inventory and impact analysis from Civil Defense records (2000-2024); (iii) multitemporal land-use change assessment (MapBiomas 1985-2023) revealing wetland loss and urban expansion patterns; (iv) socioeconomic data from IBGE Census 2022 and Brazilian Water Agency (ANA); and (v) community perception surveys addressing extreme event experiences, preparedness levels, and adaptive strategies through structured Likert-scale questionnaires. The vulnerability assessment employs the Social Vulnerability Index (SoVI) and Pressure and Release (PAR) model through Analytical Hierarchy Process (AHP) and Weighted Linear Combination (WLC) in QGIS environment. Key variables include: extreme event exposure (historical flood zones, rainfall intensity patterns, proximity to water bodies, topographic elevation from Digital Elevation Models), social sensitivity (income levels, educational attainment, demographic density, housing precariousness, vulnerable age groups), and adaptive capacity (early warning system access, infrastructure quality, land tenure security, community organization). Preliminary results from 80% completed planialtimetric surveys and 60% aerial mapping reveal critical spatial patterns linking historical extreme events to vulnerability hotspots. Analysis indicates that areas experiencing the 2015 floods show continued high-risk occupation, inadequate drainage systems, and limited post-disaster recovery interventions. The 2024 mega-disaster has reinforced these patterns, demonstrating how climate change amplifies vulnerability in territories lacking adequate risk governance and territorial planning. The study proposes Nature-Based Solutions (NbS) as primary adaptation measures: wetland restoration for flood buffering capacity, green infrastructure for stormwater management, riparian forest recovery for erosion control, and ecosystem-based disaster risk reduction strategies. Additionally, recommendations include early
warning system enhancement, community-based monitoring networks, and riskinformed territorial zoning integrated with municipal master plans and climate adaptation policies. These findings directly support CRIEC's strategic mission of developing innovative solutions for extreme climate events and strengthening Rio Grande do Sul's capacity as an international hub for climate science and disaster response. The transdisciplinary framework provides replicable methodologies for risk assessment in climate-vulnerable coastal territories across Latin America and similar contexts globally.