From Deterministic Safety to Probabilistic Risk: A Reliability-Based Framework for Riverbank Stability under Rapid Drawdown Conditions
DOI:
https://doi.org/10.29227/IM-2026-01-01-025Keywords:
riverbank stability, probabilistic analysis, monte carlo simulation, rapid drawdown, reliability - based design, limit equilibrium method (gle), geotechnical uncertainty, probability of failureAbstract
Riverbank instability is a critical geotechnical hazard exacerbated by increasing hydrological extremes under climate change. Conventional deterministic approaches based on a single Factor of Safety (FoS) often fail to capture the inherent uncertainty in soil properties and transient hydraulic conditions, leading to a misleading “illusion of safety.” This study develops an integrated probabilistic framework that couples transient seepage analysis with the General Limit Equilibrium (GLE) method and Monte Carlo Simulation (MCS) using Latin Hypercube Sampling (LHS). Key geotechnical parameters are modelled as random variables to explicitly quantify uncertainty, while rapid drawdown (RDD) is simulated to capture the most critical failure condition. A representative riverbank case study demonstrates that although deterministic analysis yields a marginally stable FoS of 1.04 under RDD conditions, the probabilistic results indicate a high Probability of Failure (Pf ≈ 38.5%) and a low Reliability Index (β ≈ 0.29). Sensitivity analysis reveals that effective cohesion of the upper cohesive layer governs more than 50% of the variability in stability. Based on extensive simulations, a novel risk-based design chart using iso-probability contours is proposed, providing a more robust alternative to traditional FoS-based design. The findings highlight the need to adopt reliability-based approaches for resilient riverbank management.
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