Social Carrying Capacity of Mass Tourist Sites: Theoretical and Practical Issues about its Measurement

Congestion is an important management problem at mass tourist sites. This essay focuses on the social carrying capacity (SCC) of a tourist site as indicator of residents’ and visitors’ perception of crowding, intended as the maximum number of visitors (MNV) tolerated. In case of conflict between the residents’ MNV tolerated and the visitors’ MNV tolerated, the policy-maker has to mediate. We consider the case in which the residents’ SCC is lower than the visitors’ SCC, and the site SCC is the result of a compromise between these two aspects of the SCC. This can be measured by making reference to two criteria of choice: the utility maximisation criterion and the voting rule. The use of one method rather than the other depends on the data available about the individual preferences on crowding. Assuming that individual preferences are known, a maximisation model for the computation of the site SCC is conceived. It represents the case in which the residents’ SCC is the limiting factor. The site SCC is intended as the number of visitors which maximises the social welfare function. Because a local policy-maker maximises the welfare of residents, in this model visitors are represented by those residents whose welfare wholly depends on the tourism sector, while the social costs due to crowding are borne by those residents who are partially or totally independent from tourism. Nevertheless, in practice, the individual preferences about crowding are not always known. In this case, the MNV tolerated can be computed by applying the majority voting rule. It is shown that, under certain conditions, the optimum number of visitors, obtained through a maximisation model, is equal to the MNV tolerated by the majority of voters.Sustainable tourism development, Tourism carrying capacity, Social carrying capacity, Maximisation criterion, Majority voting rule, Overcrowding, Mass tourist site

Structure-preserving desynchronization of minority games

Perfect synchronicity in N-player games is a useful theoretical dream, but communication delays are inevitable and may result in asynchronous interactions. Some systems such as financial markets are asynchronous by design, and yet most theoretical models assume perfectly synchronized actions. We propose a general method to transform standard models of adaptive agents into asynchronous systems while preserving their global structure under some conditions. Using the minority game as an example, we find that the phase and fluctuations structure of the standard game subsists even in maximally asynchronous deterministic case, but that it disappears if too much stochasticity is added to the temporal structure of interaction. Allowing for heterogeneous communication speeds and activity patterns gives rise to a new information ecology that we study in detail

On the additional boundary condition of wind-driven ocean models on the eastern coast

In the homogeneous model of the wind-driven ocean circulation, the dynamics of the basin interior is basically governed by the Sverdrup balance and the related no mass-flux condition on the eastern boundary of the basin, which we assume to be square for conceptual simplicity. In the presence of lateral diffusion of relative vorticity, the additional condition on the eastern boundary (like the conditions on the other boundaries) is not demanded on physical grounds but it is arbitrary to a large extent. Hence, certain choices of such boundary condition can produce overall solutions which are “far” from that of Sverdrup in the eastern part of the domain, without any physical reason. In the present note we show that this discrepancy can be strongly reduced if the adopted additional boundary condition has the same form as that implicitly satisfied by the Sverdrup solution. Unlike the common approach, a criterion is thus derived which selects a suitable partial slip boundary condition according to the specific wind-stress field which is taken into account

On the benthic Ekman layer

A review of the standard model of the benthic Ekman layer is presented and reformulated in terms of relative vorticity in place of horizontal current. In this context, the possibility to use mixed boundary conditions to model this layer is explored. The related model solutions can be cast into two main groups: the first is a generalization of the classical Ekman result, while the second one has some unexpected features which are problematic with respect to the Ekman pumping process. An investigation on the finite amplitude stability via the Lyapunov method shows that solutions belonging to the first group are stable while, in the second group, solutions are unstable. This fact poses a physical constraint to the set of the admissible boundary conditions. Finally, a connection between mass transport and boundary condition at the sea floor is numerically investigated

The role of Internal Solitary Waves on deep-water sedimentary processes. The case of up-slope migrating sediment waves off the Messina Strait

Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary “current” that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities

Model Reduction for Parametrized Optimal Control Problems in Environmental Marine Sciences and Engineering

We propose reduced order methods as a suitable approach to face parametrized optimal control problems governed by partial differential equations, with applications in en- vironmental marine sciences and engineering. Environmental parametrized optimal control problems are usually studied for different configurations described by several physical and/or geometrical parameters representing different phenomena and structures. The solution of parametrized problems requires a demanding computational effort. In order to save com- putational time, we rely on reduced basis techniques as a reliable and rapid tool to solve parametrized problems. We introduce general parametrized linear quadratic optimal control problems, and the saddle-point structure of their optimality system. Then, we propose a POD-Galerkin reduction of the optimality system. Finally, we test the resulting method on two environmental applications: a pollutant control in the Gulf of Trieste, Italy and a solution tracking governed by quasi-geostrophic equations, in its linear and nonlinear version, describing North Atlantic Ocean dynamic. The two experiments underline how reduced order methods are a reliable and convenient tool to manage several environmental optimal control problems, for different mathematical models, geographical scale as well as physical meaning