Material Controls on Landslide-Dam Breach Evolution and Hydrograph Response: A Review

Abstract

Landslide-dam breaching can generate short-lived, high-magnitude outburst floods, but breach hydrograph prediction remains limited by uncertainty in dam material properties. This review synthesises experimental, field, and modelling evidence through a process chain-linking grain-size distribution (GSD) and inherited facies structure to erosion resistance, seepage preconditioning, breach evolution, residual morphology, and hydrograph characteristics. Across the reviewed evidence, material effects are response specific and remain conditioned by hydraulic loading and dam geometry. Controlled experiments report non-monotonic peak-discharge responses to median grain size (D50) and coarse particle fraction (Fc), with fine-rich and coarse-rich end members suppressing, delaying, or reshaping the hydrograph through different pathways. A single D50 is therefore insufficient for heterogeneous or bimodal materials. GSD shape, fines and coarse fractions, packing state, and inherited facies influence different components of erosion initiation, sediment export, seepage response, and residual breach geometry. Pre-breach seepage and size-selective erosion can also alter the active material state, making resistance dependent on breach stage and location. Evidence is strongest for these directional process links; quantitative transfer remains limited by experimental scale, material preparation, hydraulic forcing, and parameter-estimation method. For rapid assessment, the synthesis therefore favours multi-descriptor observations used to define bounded, stage-dependent parameter ranges or sensitivity cases, with material uncertainty propagated to hydrograph prediction and downstream outburst-flood assessment.