Large-scale landslide dams may block the river flow and cause inundation upstream, and subsequently fail and result in severe flooding and damage in the downstream. The need for enhanced understanding of the inundation and flooding is evident. This article presents an experimental study of the inundation and landslide dam-break flooding over erodible bed in open channels. A set of automatic water-level probes is deployed to record the highly transient stage, and the post-flooding channel bed elevation is measured. New experimental data resources are provided for understanding the processes of landslide-induced flooding and for testing mathematical rivers models.
Upwind algorithms are becoming progressively popular for river flood routing due to their capability of resolving trans-critical flow regimes. For consistency, these algorithms suggest natural upwind discretization of the source term, which may be essential for natural channels with irregular geometry. Yet applications of these upwind algorithms to natural river flows are rare, and in such applications the traditional and simpler pointwise, rather than upwind discretization of the source term is used. Within the framework of a first-order upwind algorithm, this paper presents a comparison of upwind and pointwise discretizations of the source term. Numerical simulations were carried out for a selected irregular channel comprising a pool-riffle sequence Jn the River Lune, England with observed data. It is Shown that the impact of pointwise discretization, compared to the upwind, is appreciable mainly in flow zones with the Froude number closer to or larger than unity. The discrepancy due to pointwise and upwind discretizations of the source term is negligible in flow depth and hence in water surface elevation, but well manifested in mean velocity and derived flow quantities. Also the occurrence of flow reversal and equalisation over the pool-riffle sequence in response to increasing discharges is demonstrated.
Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime,for which traditional decoupled mathematical river mod-els based on simplified conservation equations are not applicable. A two-dimen-sional coupled mathematical model is presented,which is generally applicable to the fluvial processes with either intense or weak sediment transport. The governing equations of the model comprise the complete shallow water hydrodynamic equa-tions closed with Manning roughness for boundary resistance and empirical rela-tionships for sediment exchange with the erodible bed. The second-order Total-Variation-Diminishing version of the Weighted-Average-Flux method,along with the HLLC approximate Riemann Solver,is adapted to solve the governing equations,which can properly resolve shock waves and contact discontinuities. The model is applied to the pilot study of the flooding due to a sudden outburst of a real glacial-lake.
