Section: Systems and Control
Tutor: FAGIANO LORENZO MARIO
Advisor: CASTELLETTI ANDREA FRANCESCO Major Research topic
:A dynamic, basin-scale river sediment connectivity model for dam management impact assessmentAbstract:
River sediment connectivity plays a fundamental role in the safeguard of the health of the fluvial ecosystems and the availability of ecosystem goods and services for human use. Anthropic disturbances to natural sediment transport processes caused, e.g., by dam construction and management or deforestation, are hence potentially detrimental to river ecosystems and ecosystem services. By their nature, rivers are deeply interconnected systems. Thus, the alteration of the natural sediment transport processes in one or multiple locations may have cumulative impacts on the whole network; however, this risk is often underestimated or ignored while planning human interventions around or on river systems. This is also due to the lack of fast, reliable and data-parsimonious tools for modelling sediment connectivity alteration with a network prospective.
My thesis focuses on the development of a new dynamic modelling framework for the evaluation of basin-scale sediment routing processes in river network. This new framework aims to describe sediment transport in term of transfer rate through space and time, taking into consideration multiple factors that can affect the transport, such as spatial and temporal variations in water discharge and river geomorphological features (i.e. river gradient and width), different sediment grainsizes, sediment entraining and deposition from and in the river bed and interaction between sediment coming from different sources.
The new framework will employ the consistent large-scale geomorphological and hydrological data available from modern remote-sensing and modelling techniques to estimate sediment connectivity in large and data scarce case studies, where traditional morphodynamic models cannot be employed.
The model will also account for the presence of external sediment input from the watershed and from human activities, e.g. bank gravel mining or deforestation, and the presence, location and design of dams. Therefore, the new dynamic framework will be able to conduct impact assessment analysis on sediment connectivity due to anthropic development projects in the network. In particular, we will focus on dam siting and dam management strategies. To do so, specific indicators of connectivity alteration will be developed.
With this new modelling framework, we aim to provide an efficient tool to assess basin-scale river sediment routing. The novelty of the model stands in its dynamic framework, which allows for the consideration of the timing of the routing of the sediment fluxes in the network, the quantification of the different delivery times and synchronization of sediment delivery processes and the exploration of the impact of dam operational policy, and not only planning, on sediment connectivity (e.g. bottom gate use or flushing). The model could then be used in multi-objective analysis frameworks of large-scale projects on river network, like dam development, land use change and river restoration projects; in order to evaluate the different impacts on river sediment connectivity.