Spatial and temporal lag effects in bedload sediment transport
Thesis DisciplineCivil Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Spatial lag effects and temporal lag effects are investigated under bedload sediment transport conditions. This investigation, which involves both experimental and theoretical studies, culminates in the formulation of a numerical model which includes schemes which successfully describe spatial and temporal lag effects. An equation which characterises spatial lag effects and two possible relations for the spatial lag coefficient are investigated. Values of the spatial lag coefficient are calculated from measured data and compared with values predicted by the theoretical relations. This investigation verifies the proposed spatial lag equation and indicates the form of the spatial lag coefficient relation. A temporal lag scheme which is able to predict the temporal variation of bed roughness and sediment transport capacity under non-steady flow conditions is developed and calibrated against measured data. An impulse model is used to predict the temporal variation of the variable which chracterises the temporal response of the alluvial system, the equivalent steady flow rate. The performance of the temporal lag scheme is tested against additional measured data which verifies the proposed temporal lag scheme. A numerical model which incorporates the spatial lag equation and the temporal lag scheme is formulated. This model also incorporates an upstream sediment boundary scheme which takes account of the zone of separation in a scour hole. The performance of the numerical model is tested against data measured by a previous investigator. The ability of the numerical model to predict the spatial and temporal variation of the bed elevation and the bedload sediment transport rate under both steady and non-steady flow, non-equilibrium sediment transport conditions is verified.