Hydraulic hazard mapping in alpine dam break prone areas: the Cancano dam case

Dam-break hazard assessment is of great importance in the Italian Alps, where a large number of medium and large reservoirs are present in valleys that are characterized by widespread urbanized zones on alluvial fans and along valley floors. Accordingly, there is the need to identify specific operative approaches in order to quantify hydraulic hazard which in mountain regions inevitably differ from the ones typically used in flat flood-prone areas. These approaches take advantage of: 1) specific numerical algorithms to pre-process the massive topographic information generally needed to describe very irregular bathymetries; 2) an appropriate mathematical model coupled with a robust numerical method which can deal in an effective way with variable geometries like the ones typical of natural alpine rivers; 3) suitable criteria for the hydraulic hazard assessment; 4) representative test cases to verify the accuracy of the overall procedure. This contribution presents some preliminary results obtained in the development of this complex toolkit, showing its application to the test case of the Cancano dam-break, for which the results from a physical model are available. This case was studied in 1943 by De Marchi, who investigated the consequences of the potential collapse of the Cancano dam in Northern Italy as a possible war target during the World War II. Although dated, the resulting report (De Marchi, 1945) is very interesting, since it mixes in a synergistic way theoretical, experimental and numerical considerations. In particular, the laboratory data set concerning the dam-break wave propagation along the valley between the Cancano dam and the village of Cepina provides an useful benchmark for testing the predictive effectiveness of mathematical and numerical models in mountain applications. Here we suggest an overall approach based on the 1D shallow water equations that proved particularly effective for studying dam-break wave propagation in alpine valleys, although this kind of problems is naturally subject to "substantial uncertainties and unavoidable arbitrarinesses" (translation from De Marchi, 1945). The equations are solved by means of a shock-capturing finite volume method involving the Pavia Flux Predictor (PFP) scheme proposed by Braschi and Gallati (1992). The comparison between numerical results and experimental data confirms that the mathematical model adopted is capable of capturing the main engineering aspects of the phenomenon modeled by De Marchi

A multi-century meteo-hydrological analysis for the Adda river basin (Central Alps). Part I: Gridded monthly precipitation (1800–2016) records

The 1800–2016 monthly precipitation record for the upper Adda river basin is presented. It is computed by applying the anomaly method to a quality-checked and homogenized observation database. The reconstruction accuracy and its evolution over the study period is evaluated at both station and grid-cell levels. The anomaly-based interpolation provides rather robust estimates even for the early years of sparse station coverage with basin precipitation reconstruction errors around 10%. The Theil-Sen trend analysis on the basin precipitation series shows significant (Mann-Kendall p value <.05) long-term tendencies of −3.8 ± 1.9% and −9.3 ± 3.8% century−1 for annual and autumn precipitation, respectively, even though the annual trend is not significant by excluding the first decades from the evaluation. As the basin precipitation record is expected to be underestimated due to the rain-gauge snow undercatch, the monthly precipitation fields are subjected to a correction procedure which allows to derive the multiplicative correcting constant to be applied to the basin annual precipitation series. The comparison between 1845 and 2016 yearly corrected precipitation and runoff records highlights current annual water losses of about 400 mm while the annual runoff coefficients exhibit a long-term significant decrease of −6.4 ± 1.0% century−1. This change in the hydrological cycle is mostly to be ascribed to the strong long-term reduction in annual runoff values (−11.8 ± 3.2% century−1) driven by increasing evapotranspiration due to both temperature increase and, likely, land-use changes

Osteopontin shapes immunosuppression in the metastatic niche.

The matricellular protein osteopontin (OPN, Spp-1) is widely associated with cancer aggressiveness when produced by tumor cells, but its impact is uncertain when produced by leukocytes in the context of the tumor stroma. In a broad study using Spp1(-/-) mice along with gene silencing in tumor cells, we obtained evidence of distinct and common activities of OPN when produced by tumor or host cells in a spontaneously metastatic model of breast cancer. Different cellular localization of OPN is associated with its distinct activities, being mainly secreted in tumor cells while intracellular in myeloid cells. OPN produced by tumor cells supported their survival in the blood stream, whereas both tumor- and host-derived OPN, particularly from myeloid cells, rendered the metastatic site more immunosuppressive. Myeloid-derived suppressor cells (MDSC) expanded with tumor progression at both primary and lung metastatic sites. Of the expanded monocytic and granulocytic cell populations of MDSCs, the monocytic subset was the predominant source of OPN. In Spp1(-/-) mice, the inhibition of lung metastases correlated with the expansion of granulocyte-oriented MDSCs. Notably, monocytic MDSCs in Spp1(-/-) mice were less suppressive than their wild-type counterparts due to lower expression of arginase-1, IL6, and phospho-Stat3. Moreover, fewer regulatory T cells accumulated at the metastatic site in Spp1(-/-) mice. Our data find correlation with lung metastases of human mammary carcinomas that are associated with myeloid cells expressing OPN. Overall, our results unveiled novel functions for OPN in shaping local immunosuppression in the lung metastatic niche

Three-Dimensional Numerical Modelling of Real-Field Dam-Break Flows: Review and Recent Advances

Numerical modelling is a valuable and effective tool for predicting the dynamics of the inundation caused by the failure of a dam or dyke, thereby assisting in mapping the areas potentially subject to flooding and evaluating the associated flood hazard. This paper systematically reviews literature studies adopting three-dimensional hydrodynamic models for the simulation of large-scale dam-break flooding on irregular real-world topography. Governing equations and numerical methods are analysed, as well as recent advances in numerical techniques, modelling accuracy, and computational efficiency. The dam-break case studies used for model validation are highlighted. The advantages and limitations of the three-dimensional dam-break models are compared with those of the commonly used two-dimensional depth-averaged ones. This review mainly aims at informing researchers and modellers interested in numerical modelling of dam-break flow over real-world topography on recent advances and developments in three-dimensional hydrodynamic models so that they can better direct their future research. Practitioners can find in this review an overview of available three-dimensional codes (research, commercial, freeware, and open-source) and indications for choosing the most suitable numerical method for the application of interest

New formulation of the two-dimensional steep-slope shallow water equations. Part I: Theory and analysis

Two-dimensional (2D) depth-averaged shallow water equations (SWE) are widely used to model unsteady free surface flows, such as flooding processes, including those due to dam-break or levee breach. However, the basic hypothesis of small bottom slopes may be far from satisfied in certain practical circumstances, both locally at geometric singularities and even in wide portions of the floodable area, such as in mountain regions. In these cases, the classic 2D SWE might provide inaccurate results, and the steep-slope shallow water equations (SSSWE), in which the restriction of small bottom slopes is relaxed, are a valid alternative modeling option. However, different 2D formulations of this set of equations can be found in the geophysical flow literature, in both global horizontally-oriented and local bottom-oriented coordinate systems. In this paper, a new SSSWE model is presented in which water depth is defined along the vertical direction and flow velocity is assumed parallel to the bottom surface. This choice of the dependent variables combines the advantages of considering the flow velocity parallel to the bottom, as can be expected in gradually varied shallow flow, and handling vertical water depths consistent with elevation data, usually available as digital terrain models. The pressure distribution is assumed linear along the vertical direction and flow curvature effects are neglected. A new formulation of the 2D depth-averaged SSSWE is derived, in which the two dynamic equations represent momentum balances along two spatial directions parallel to the bottom, whose horizontal projections are parallel to two fixed orthogonal coordinate directions. The analysis of the mathematical properties of the new SSSWE equations shows that they are strictly hyperbolic for wet bed conditions and reduce to the conventional 2D SWE when bottom slopes are small. Finally, it is shown that the SSSWE predict a slower flow compared with the conventional SWE in the theoretical case of a 1D dam-break on a frictionless channel with fixed slope. The capabilities of the proposed model are demonstrated in a companion paper on the basis of numerical and experimental tests

3D CFD analysis of the performance of oblique and composite side weirs in converging channels

Conventional rectangular side weirs installed along prismatic open-channels may have low efficiency. One practical way to overcome this problem may be to insert the weir in the oblique side of a converging channel. In this paper, the performance of oblique straight side weirs or two-segment single-cranked side weirs inserted in rectangular converging channels are analysed through 3D computational fluid dynamics (CFD) for subcritical steady flow conditions. The numerical simulations were performed through a widely available software package by applying the VOF method to the Reynolds-averaged Navier–Stokes equations and adopting the Reynolds stress model for turbulence closure. The model is validated against experimental data previously obtained by the authors. The results provide insight into the features of the flow field and show the effect of the channel contraction rate on diversion efficiency. As regards the two-segment single-cranked weir, the “concave” arrangement has been verified as being more efficient than the “convex” one

New formulation of the two-dimensional steep-slope shallow water equations. Part II: Numerical modeling, validation, and application

Numerical models based on the two-dimensional (2D) shallow water equations (SWE) are commonly used for flood hazard assessment, although the basic assumption of small bottom slopes is not always strictly satisfied, such as in mountain areas. When terrain slopes are large, the steep-slope shallow water equations (SSSWE) are theoretically more suitable because the restrictive hypothesis of small bottom slopes is not introduced in deriving these equations. A new formulation of the 2D SSSWE, in which the water depth is measured in the vertical direction, and the flow velocity is assumed parallel to the bottom surface, is proposed in the companion paper (Part I). The pressure distribution on the vertical is assumed linear (yet non-hydrostatic), and the effect of flow curvature is neglected. In this paper, the new SSSWE are solved with an explicit MUSCL-type second-order accurate finite volume scheme using the centered FORCE method for flux evaluation. The SSSWE model is validated against existing experimental data of one-dimensional (1D) dam-break flows on sloping channels with fixed slopes. The numerical results of the SSSWE and SWE models are compared both in this benchmark test case and in other numerical tests, including a 1D dam-break flow moving on an adverse slope, a 2D dam-break flow spreading on an inclined plane, and a 2D dam-break flow propagating in a sloping parabolic channel. Finally, the two models are applied to the real-field test case of the Cancano dam (Adda River, northern Italy), which is characterized by very steep and irregular topography, especially in the upper portion of the valley. The results show that, on the whole, the SSSWE are more accurate in describing dam-break flows over steep topographies than the conventional SWE and predict less severe flooding with slower wave propagation. The two models are practically equivalent when bottom slopes are relatively small