Simplified models for morphological evolution of river and lagoon systems

Morphodynamics of sedimentary systems is nowadays a fundamental piece of knowledge for civil and environmental engineers involved in fluvial and lagoonal interventions. While morphodynamics is in principle an extremely complex discipline, some fundamental results may be achieved with relatively simple models. Purpose of the present dissertation is providing an analysis of a number of simplified models, discussing the usefulness of their approach and the limits of their applications. The entire study is especially on the analytical and numerical analysis of simplified one-dimensional formulations of fluvial morphodynamics and two-dimensional formulations of lagoon morphodynamics. Chapter 1: A general description and literature review of the sedimentation processes and morphological models are introduced. Chapter 2: Numerical procedures are applied to solve mathematical models that represents hydraulic and morphological aspects of simplified river (Peviani, 2002, Fasolato et al., 2006a). Chapter 3: The objective of the river model analytical analysis is to study the effects of geometry, hydrology and sediment input unsteadiness and non-uniformities, by explicitly indicating the most important parameters that control their propagation and attenuation along the river (Fasolato et al., 2008a). Chapter 4: Are analyzed here the validity and limitations of the local uniform water flow hypothesis (Fasolato et al., 2008b), an extremely useful simplification for large time- and space-scale computations and the only one which permits to cope with large unsurveyed watersheds (Ronco et al., 2008a). Chapter 5: Scope of the study, for the lagoon morphodynamics, is to reproduce and valuate the branching channel generation in a short tidal basin with a long term morphological model. In a schematic lagoon, the network ontogeny and the subsequent morphological bottom evolution are reproduced; consequently the planimetric and altimetrical features are analyzed and compared to the state of the system energy (Fasolato et al., 2008c). Finally, general results and further developments are discussed, underlining, however, that all simplified the models analyzed in this dissertation require further verifications against experimental or field measurements.