PHYSICAL AND NUMERICAL MODELING OF DELTAIC SEDIMENTATION IN LAKES AND RESERVOIRS

摘要

Deltas form where rivers meet standing bodies of water such as lakes and reservoirs. A delta is composed of a coarse-grained fluvially-deposited topset, a coarsegrained prograding foreset deposited by grain avalanching and a fine-grained bottomset deposited from a surface sediment plume or a plunging turbidity current. Here the case of a 1D delta in a body of fresh water with a bottomset emplaced by a plunging turbidity current is considered. The authors have previously developed a moving-boundary numerical model pertaining to such deltas. In that model the coarse-grained material is characterized with a single sand size and the fine-grained material is characterized with a single mud (silt-clay) size that drives the plunging turbidity current. Here the analysis is extended to the case for which the turbidity current is driven by two agents: mud and dissolved salt. Salt serves as a surrogate for a mud so fine that its fall velocity can be neglected. The results of the numerical model are tested against an experiment.