Mauro Fiorentino

Derived distribution of floods based on the concept of partial area coverage with a climatic appeal

A new rationale for deriving the probability distribution of floods and help in understanding the physical processes underlying the distribution itself is presented. On the basis of this a model that presents a number of new assumptions is developed. The basic ideas are as follows: (1) The peak direct streamflow Q can always be expressed as the product of two random variates, namely, the average runoff per unit area ua and the peak contributing area a; (2) the distribution of ua conditional on a can be related to that of the rainfall depth occurring in a duration equal to a characteristic response time тa of the contributing part of the basin; and (3) тa is assumed to vary with a according to a power law. Consequently, the probability density function of Q can be found as the integral, over the total basin area A of that of a times the density function of ua given a. It is suggested that ua can be expressed as a fraction of the excess rainfall and that the annual flood distribution can be related to that of Q by the hypothesis that the flood occurrence process is Poissonian. In the proposed model it is assumed, as an exploratory attempt, that a and ua are gamma and Weibull distributed, respectively. The model was applied to the annual flood series of eight gauged basins in Basilicata (southern Italy) with catchment areas ranging from 40 to 1600 km2. The results showed strong physical consistence as the parameters tended to assume values in good agreement with well-consolidated geomorphologic knowledge and suggested a new key to understanding the climatic control of the probability distribution of floods.

Geographical information systems in hydrology

Preface. 1. Hydrologic modeling with GIS V.P. Singh, M. Fiorentino. 2. Integration of Remote Sensing and GIS for Hydrologic Studies S.F. Shih. 3. Hydrologic Data Development M.L. Wolfe. 4. Spatial Data Characteristics C.A. Quiroga, et al. 5. Methods for Spatial Analysis E.B. Moser, R.E. Macchiavelli. 6. GIS Needs and GIS Software C. Collet, et al. 7. Digital Terrain Modelling A. Sole, A. Valanzo. 8. GIS for Distributed Rainfall - Runoff Modeling C. Colsoimo, G. Mendicino. 9. GIS for Large-Scale Watershed Modelling G.W. Kite, et al. 10. Lumped Modeling and GIS in Flood Prediction I. Muzik. 11. GIS in Groundwater Hydrology S. Gupta, et al. 12. Nonpoint Source Pollution Modeling (with GIS) C.T. Haan, D.E. Storm. 13. Soil Erosion Assessment Using GIS A.P.J. de Roo. 14. A Study of Landslides Based on GIS Technology T.P. Gostelow. 15. Land-Use Hydrology C.A. Quiroga, et al. 16. Design of GIS for Hydrological Applications G. Mendicino. List of Contributors. Subject Index.

An entropy‐based morphological analysis of river basin networks

Under the assumption that the only information available on a drainage basin is its mean elevation, the connection between entropy and potential energy is explored to analyze drainage basins morphological characteristics. The mean basin elevation is found to be linearly related to the entropy of the drainage basin. This relation leads to a linear relation between the mean elevation of a subnetwork and the logarithm of its topological diameter. Furthermore, the relation between the fall in elevation from the source to the outlet of the main channel and the entropy of its drainage basin is found to be linear and so is also the case between the elevation of a node and the logarithm of its distance from the source. When a drainage basin is ordered according to the Horton-Strahler ordering scheme, a linear relation is found between the drainage basin entropy and the basin order. This relation can be characterized as a measure of the basin network complexity. The basin entropy is found to be linearly related to the logarithm of the magnitude of the basin network. This relation leads to a nonlinear relation between the network diameter and magnitude, where the exponent is found to be related to the fractal dimension of the drainage network. Also, the exponent of the power law relating the channel slope to the network magnitude is found to be related to the fractal dimension of the network. These relationships are verified on three drainage basins in southern Italy, and the results are found to be promising.

New insights about the climatic and geologic control on the probability distribution of floods

An application of the theoretically based distribution of floods recently derived by Iacobellis and Fiorentino [2000] was carried out with the aim of analyzing the climatic and geologic control on the distribution itself. In particular, 20 basins in a wide area of southern Italy were considered. These basins were classified by the use of a climatic index I depending on the average annual rainfall and on the potential evapotranspiration. This index takes positive values in humid climates and negative values in dry zones. With regard to the geology, attention was paid to the watershed permeability during intense storms; in each basin the pervious area was estimated after identification of three permeability classes. The analyses demonstrated that the sign of the climatic index strongly discriminates the behavior of both the parameters ƒA and E[a], the former representing, for each basin, the characteristic total abstraction rate and the latter being the expected value of the basin area contributing to the flood peak. In dry zones, ƒA was found to decrease with increasing A, and the ratio r = E[a]/A tended to decline linearly, as the percentage of pervious areas increased. On the contrary, in humid zones the basin area did not seem to have any effect on ƒA, which was instead particularly sensitive to the climatic index. Moreover, in these zones the parameter r was steadily low without showing any significant dependence on climate, geology, and morphology of the basin. In this paper, an interpretation of these results is indeed provided.

Entropy and energy dissipation in water resources

Perspectives on entropy and energy dissipation application of entropy in hydrology application of entropy in water resources application of entropy in hydraulics application of energy principles in hydrology application of energy principles in hydraulics.

Entropy approach for 2D velocity distribution in open-channel flow

In this paper, considering time-averaged velocity as a random variable, two-dimensional (2D) velocity distributions in open-channel flow have been derived based on the Shannon entropy concept and the principle of maximum entropy. The velocity distributions so derived have limited practical use, since they contain too many parameters that need to be experimentally calibrated and hence are not convenient to apply. This work develops a new entropy-based approach for deriving a 2D velocity distribution in open-channel flow, thereby investigating a rectangular geometric domain. The derived distribution is parsimonious, and the values determined using the proposed distribution are found to be in good agreement with the experimentally-measured velocity values.

Informational entropy of fractal river networks

Abstract Informational entropy of river networks, as defined by Fiorentino and Claps (1992x), proved to be a useful tool in the interpretation of several properties exhibited by natural networks. In this paper, self-similar properties of river networks are taken as the starting point for investigating analogies and differences between natural networks and geometric fractal trees, comparing their variability entropy with parameters of both classes of networks. Attention is directed particularly to relations between entropy and Horton order and entropy and topological diameter of subnetworks. Comparisons of these relations for fractals and natural networks suggest that network entropy can contribute to clarify important points concerning self-similar properties of river networks. Moreover, the estimation of the fractal dimension of branching for natural networks can be considerably improved using the relation between entropy and Horton order throughout the network.

Hydraulic features of supercritical flow along prismatic side weirs

Side weirs are key structures often located in combined sewer systems, provided the upstream flow is subcritical. At present, knowledge of the outflow process when the flow along the weir is subcritical can be considered satisfactory. The same cannot be said when, as often happens in practice, the upstream flow is subcritical while the flow along the weir is supercritical. In this paper the local flow features along prismatic side weirs in a circular channel were investigated. In particular, the condition of supercritical flow along the weir was analysed. Based on experimental work and on data available in the literature, some characteristics of both the flow that remains in the main channel and the flow that leaves it were investigated. These include: the distribution of the discharge in the main channel, the lateral outflow angle and the lateral outflow velocity. The results combine to provide a better understanding of the outflow process and are also readily applicable for design. Finally, a theoretical global approach is presented to estimate the head loss due to the flow partition.

Probabilistic Flow Duration Curves for Use in Environmental Planning and Management

When dealing with the planning and management of water uses in a river, the knowledge of the probabilistic structure of minima of daily or of multiple-day flows is often required. As a tool for straightforward determination of different levels of flow minima, flow duration curves (FDCs) are particularly suited for planning purposes. In this paper, FDCs referred to annual samples are interpolated with lognormal curves, and their probabilistic structure is obtained through the statistical analysis of the two lognormal parameters. Distribution of these parameters is shown to be normal so that the discharge with a given duration and return period T can be easily evaluated. To build FDCs in ungaged basins, relations between the moments of the parameters and catchment characteristics have been investigated with reference to the data available in the Basilicata region (Italy). For both parameters, most of the variance of the first moment can be explained by the Base Flow Index (BFI), which can be estimated from geology. The second moment can be derived considering that the coefficient of variation is constant over the whole region. Since the curves are considered in dimensionless form, estimation of the mean annual runoff is finally needed to obtain the dimensional probabilistic FDCs in ungaged sites.

A HISTORICAL PERSPECTIVE OF ENTROPY APPLICATIONS IN WATER RESOURCES

Entropy and the principle of maximum entropy are being increasingly applied to a wide range of problems in hydrology and water resources. This paper reviews some of the hydrologic applications of entropy, and comments on the entropy-based approaches. Entropy is a powerful model-building tool, and its potential in explaining the great many hydrologic processes remains largely untapped.