Process-based distributed modelling of basin-scale sediment dynamics

2017-01-31T04:49:11Z (GMT) by Kabir, Md Aynul
In this thesis, we propose a novel Process-based Distributed Sediment Dynamic Model (PDSDM) to estimate watershed sediment budgets at spatiotemporal scales, with due consideration of the suspended loads, bed loads and their interactions within the hillslope and channels. To overcome the limitations of existing approaches, in this model, hillslope and channel sediment dynamics have been modelled separately and the links between hillslope sediment processes and channel sediment dynamics have been strengthened. Fractional sediment loads (bed load and suspended load), their interactions and overall basin-scale sediment budgets have been investigated to represent in-stream sediment dynamics properly. Also, modelling of channel bed level variations has been linked with watershed sediment dynamics and an investigation of climate change conditions on watershed sediment dynamics has been carried out. The PDSDM has been developed by integrating an existing Distributed Hydrological Model (DHM) with newly developed sediment modules for: (i) suspended sediment dynamics at hillslope; (ii) suspended sediment dynamics at channel; (iii) bed load estimation and transport at channel; and (iv) channel bed level variations. In PDSDM, a transport capacity equation is used as one of the key parameters for estimating suspended sediment dynamics whilst the bed load transport rate is calculated by a bed load transport equation. The PDSDM has been upgraded by incorporating options to select from and use different transport capacity equations and bed load transport equations to simulate suspended and bed load transport processes in catchment areas. The model has been applied to two different hydro-climatic areas (the Abukuma River Basin in Japan and the Latrobe River Basin in Australia) to ensure its applicability. The modelling outcomes from the application areas have been found to be consistent in estimating watershed sediment dynamics. Overall, our proposed PDSDM reveals a robust sediment dynamic model that considers all relevant catchment parameters along with a detailed modelling of hillslope and channel areas separately.