Laboratory of Hydraulics and Hydraulic Constructions

carniello

 

 

Teacher in charge: Prof. Luca Carniello

 

Activity:

A first topic of the research activity focuses on tidal basin morphodynamics and geomorphology.

We develop a numerical model which aims at describing hydrodynamics and wind waves generation and propagation within shallow microtidal basins. Such a numerical approach confirmed the prominent role of wind waves in resuspending bottom sediments in shallow tidal basins. Based on this results a conceptual stability model has been proposed which indicates that the intertidal landscape in shallow basins is organized into a bimodal distribution of bottom elevations, with the two peaks corresponding to salt marshes and tidal flats, and few areas lying at intermediate elevations

We further developed a sediment transport model to be coupled to the wind wave-tidal model. The sediment transport model considers a bi granular mixture of both cohesive and non cohesive sediments and describes resuspension, deposition and related bottom evolution in term of elevation and composition.

Using the above models we study the morphological evolution of microtidal environments and of the Venice lagoon in particular, that has been experiencing an important morphological degradation since the beginning of the last century, resulting in a generalized deepening of the lagoon bottom (with negative consequences for fisheries and water quality) and extensive salt marsh losses. This is particularly significant because salt marshes — known as “blue carbon ecosystems” (i.e. the carbon that is fixed via ocean and coastal ecosystems) — rank among the most efficient biosequestration systems on Earth. Surprisingly, although these ecosystems host just 0.05% of the plant biomass on land, their high efficiency for carbon sequestration allows them to store an comparable  amount of carbon per year comparable to that stored by terrestial system. Salt marshes can accumulate organic carbon in their soils at rates up to 55-times faster than tropical rainforests, whereand they sequestrate it for millennia. It is therefore of critical importance to increase current understanding of, and accelerate action on the important role of coastal blue carbon ecosystems in climate change action, as emphasized by the climate change negotiation meetings in Paris at COP21

Following a considerably different approach the research activities also focused on the analysis of the processes that govern the formation and evolution of tidal networks using an experimental apparatus developed in the laboratory of the Department ICEA. The experiments allowed us to understand the mechanisms of formation of networks and their response to cycles of raising and lowering of the mean sea level. The future development of this line of research concerns the analysis of the effects of the cohesion of the sediment and the presence of vegetation. In parallel to these activities, conceptual (numerical and/or analytical) models have been developed for studying the long-term evolution of tidal environments considering the effect of vegetation and climate change.

The further topic of the research aims at analyzing levee stability conditions and flood wave propagation within the river network and over the adjacent rural and urban areas, as a consequence of levee failure due to levee-breach formation and development, as a consequence of surface erosion by flow overtopping or levee underseepage.