An exploration of equilibrium in Venice Lagoon using an idealised form model

A number of morphological models, often referred to as regime or hybrid models, require the equilibrium relationship between form and hydraulics to be prescribed in some way. In general, the well documented relationship between tidal prism and the cross-sectional area of the channel has been adopted. In this paper an alternative approach is proposed. First, a description of an idealised 3D morphology has been developed based on the equilibrium form of the constituent parts, namely the plan form, low water channel cross-section and intertidal profile. This is then modified to take account of waves acting on the shores of the constituent channels. A key feature of the model is that it only uses attributes that are exogenous to the system, or can be defined a priori (although there is some discussion as to how well this objective is fulfilled in relation to the sedimentary properties). The model is applied to the three inlets that make up Venice Lagoon. The quality of fit obtained is sufficient to justify a more detailed examination of the model's ability to predict the gross properties of the system (volumes and surface areas of the channels and intertidal flats), and an assessment of modelled changes in basin hypsometry against observed changes.