Abstract The necessity of updating the numerical models inputs, because of geometrical and resistive variations in rivers subject to solid transport phenomena, requires detailed control and monitoring activities. The human employment and financial resources of these activities moves the research towards the development of expeditive methodologies, able to evaluate the outflows through the measurement of more easily acquirable sizes. Recent studies highlighted the dependence of the entropic parameter on the kinematical and geometrical flow conditions. They showed a meaningful variability according to the section shape, dimension and slope. Such dependences, even if not yet well defined, could reduce the difficulties during the field activities, and also the data elaboration time. On the basis of such evidences, the relationships between the entropic parameter and the geometrical and resistive sizes, obtained through a large and detailed laboratory experience on steady free surface flows in conditions of macro and intermediate homogeneous roughness, are analyzed and discussed. Keywords Froude number, entropic parameter, roughness, water discharge. I. INTRODUCTION HE increasing need to operate on the rivers with an appropriate plan of defense and protection, besides the need of correct procedures for the flood risk forecast, requires a suitable knowledge of the flow regime in extreme conditions. Currently, the use of numeric modeling, consistently increased in the last few years both at a forecasting and controlling stage, represents one of the most valuable tools in the planning and designing activity. This tool has, though, the need of up-to- date and reliable data and information, which require field activities, both on site and in remote, not always possible due to the relative time and costs involved. For this reason, the aim of the present paper is to develop tools which could enable the evaluation of outflows in an expeditive way and with less expensive and time-consuming measurement campaigns. Recent studies on regular flows have shown the possibility to attain a model formulation, derived from the application of Domenica Mirauda is with the Department of Environmental Engineering and Physics, University of Basilicata, Potenza, PZ 85100 ITALY (phone: +39- 0971-205211; fax: +39-0971-205160; e-mail: domenica.mirauda@unibas.it). Michele Greco is with the Department of Environmental Engineering and Physics, University of Basilicata, Potenza, PZ 85100 ITALY (e-mail: michele.greco@unibas.it). Antonio Volpe Plantamura is with the Department of Environmental Engineering and Physics, University of Basilicata, Potenza, PZ 85100 ITALY (e-mail: antonio.volpeplantamura@unibas.it). maximization theories of the informational entropy ([1]-[8]), able to reconstruct the flow field and assess the water discharge in an expeditive way. Such model presents a very simple analytical structure based on the evaluation of a single parameter, which globally takes into account the influence of the cross section geometry and roughness, to be calculated by the ratio between the mean and maximum flow velocities in the considered section. The extension of such law to natural flows ([8]-[13]) seems to drive a sufficient reliability even in conditions of geometric irregularity. Some river observations produce a possible linear dependence between the mean and maximum cross section velocities, with a reduced variability of the ratio between the two velocities, generally depending on local morphology. In particular, the studies produced by [9] on the Mississippi river, in several cross sections located both in rectilinear and curvilinear riverbed stretches, have underlined a perfect linear dependence between the maximum and the mean velocity, showing a value of the parameter constant and increasing as the ratio bend radius/section width increases. The studies of the other Authors underline, instead, a large variability of the entropic parameter for the natural flows, depending on the different morphology of the investigated sections. In the last years, the studies on different cross sections of Italian rivers (Central and Southern Italy) and Algerian ones ([14], [15]) have shown the dependence between the entropic parameter, M, and the morphologic characterization of the river stretches, even if qualitative, based on the Rosgen classification [16]. In particular, they showed how the river stretches belonging to the same river shape present the same value of parameter M, while differentiating among the reaches with different morphologic characteristics. Therefore, the research of a dependence between the entropic parameter and the geometric and roughness quantities, which characterize the fluvial morphology, could be a useful support to control and monitoring the surface water resources, especially with respect to the surveying activities. However, it is important to point out that the analytical relation between the entropic parameter and the sizes , which define the local morphology of stretch, like for example the shape of the section, the roughness, the plani-altimetrical configuration, the slope of the bed, has not yet been well defined. D. Mirauda, M. Greco, and A. Volpe Plantamura Influence of the entropic parameter on the flow geometry and morphology T World Academy of Science, Engineering and Technology 60 2011 1357