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In this paper the stage-discharge relationship of a flume with a central baffle is theoretically deduced using the Buckingham-Theorem of the dimensional analysis and the self-similarity theory. The new stage-discharge equation is calibrated by the measurements carried out by Peruginelli and Bonacci using a baffle having a given throat length and five different values of the contraction ratio. Finally, for a given throat length, a relationship linking the discharge with the upstream water depth, the contraction ratio and the contracted width is deduced.

In this paper, the outflow process of a weir with an irregular shape is studied using dimensional analysis and the incomplete self-similarity theory. The new unique stage–discharge relationship, which is deduced theoretically, represents a novel and comprehensive equation to describe the weir outflow process for a full range of flow and different geometric variables of weirs, including finite-crested weirs, broad-crested weirs with positive or negative crest slope, broad-crested weirs with an upstream, downstream, or both upstream and downstream crest ramps, and, triangular weirs with an upstream or downstream ramp. Finally the proposed stage–discharge relationship is calibrated using measurements available in literature.

Calanchi are erosion landforms characterised by a heavily dissected terrain with steep, unvegetated slopes and channels with a dendritic pattern, which rapidly incise and extend headwards. Recent literature focusing on badland systems highlights their similarity with other larger fluvial landforms, stating that these behave as a full size laboratory, due to their rapid development in space and time and to the diversity of geomorphic processes involved. In this paper, a brief review of the most important results on badland research is firstly presented. Then, the morphometric similarity between calanchi and other erosion landforms is discussed. Finally, models quantitatively relating the volume of sediments eroded from calanchi landforms and a set of geometric features of their tributary areas, by exploiting the dimensional analysis and the self-similarity theory, are presented.

Nella memoria sono riportati i risultati delle indagini condotte utilizzando le distribuzioni dimensionali delle gocce di pioggia (DSD) rilevate mediante un disdrometro ottico installato, nel periodo Giugno 2006 - Marzo 2014, presso il Dipartimento di Scienze Agrarie e Forestali dell’Università degli Studi di Palermo e nel periodo Luglio 2015-Gennaio 2016 presso la stazione sperimentale di El Teularet in Spagna. Dopo aver aggregato le DSD per classi di intensità differenti in ampiezza, è stata determinata la potenza cinetica associando a ciascun diametro della DSD aggregata la relativa velocità di caduta calcolata mediante una relazione reperita in letteratura. I valori di potenza cinetica così determinati sono stati utilizzati per testare l’applicabilità delle relazioni potenza cinetica-intensità della precipitazione proposte da Wischmeier and Smith (1978) e da Brown and Foster (1987). Le misure di potenza cinetica, dimostrano l’esistenza di un valore soglia di intensità di precipitazione superato il quale il diametro mediano volumetrico e, di conseguenza, la potenza cinetica, possono essere assunti costanti. Questi risultati costituiscono una verifica dell’approccio di Wischmeier e Smith (1978).

Many process-oriented erosion prediction models reproduce rill erosion as affected by site-specific parameters, as for example, rill erodibility, and thus, their practical application requires the measurement of these parameters or their estimate. The aim of this paper was establishing a method for indirectly measuring field rill erodibility. A simple mathematical approach based on a known soil detachment equation and accounting for the rill erosion dynamic process is applied. Field measurements carried out for seven natural rainfall events occurring at the plots of the Sparacia experimental station, southern Italy, are used for indirectly measuring the rill erodibility of the investigated soil. This method needs only the knowledge of the geometric characteristics of the rills at the end of the erosion event and the event duration. The method was also tested by using the Water Erosion Prediction Project database, and this analysis showed that a reliable value of rill erodibility can be obtained by the proposed Equation 18. The proposed method has the following advantages: (i) to be applicable at field scale, being more realistic than the laboratory scale because the soil structure is not destroyed, and (ii) to avoid the disadvantages of field experiments such as the cumbersome experimental set-up and the large volume of water inflow needed

Flumes for indirect discharge measurements are widespread and are characterized by a particular shape of the cross section area with various degrees of convergence and subsequent divergence. The flume named Samani, Magallanez, Baiamonte, Ferro (SMBF) is a simple and inexpensive instrument and its channel contraction is obtained by applying two semicylinders to the walls of a rectangular cross section. At first, in this paper a new stage-discharge equation for the SMBF flume is theoretically deduced. Then, this equation is experimentally calibrated using the laboratory measurements from the literature for different values of the contraction ratio. Finally the field measurements carried out at Sparacia experimental area (Sicily, South Italy) by a SMBF flume inserted into a horizontal flume and characterized by a contraction ratio equal to 0.5, are used for testing both the new stage-discharge relationship and the one originally proposed in the literature.

Major limitations of current studies on assessing the impacts of climate and land-use changes are lack of: (i) good quality observational data and model parameters, especially the soil hydraulic characteristics, and (ii) information on how the nature of spatial variability of soils affects the soil hydrologic response over a range of scales. Traditional methods for soil hydraulic characterization are burdensome, whereas information on soil spatial variability are particularly relevant for certain studies, such as distributed hydrologic modelling and precision agriculture. All these issues are particularly relevant when assessing the effects that hydrologic and sediment connectivity exerts on land and water resources management and soil erosion.

Lo sviluppo iniziale dei rill può essere spiegato facendo ricorso alle caratteristiche idrauliche della corrente, quali la velocità media, il numero di Froude e la tensione tangenziale al fondo della corrente. Gli studi già condotti sull’idraulica dei rill hanno permesso di modellizzare la geometria idraulica dei solchi mediante un set di tre equazioni, di forma potenziale, che legano la velocità media u, il tirante medio h e la larghezza del solco w alla portata. L’obiettivo del presente lavoro è stato quello di verificare l’applicabilità delle suddette relazioni potenziali e determinare i relativi coefficienti facendo ricorso alle misure condotte su 33 siti sperimentali che costituiscono il data-base del progetto WEPP. I siti si caratterizzano per una notevole variabilità delle caratteristiche tessiturali dei suoli e per valori della pendenza s dei rill variabile tra 3.8 e 12.8%. L’analisi ha confermato l’applicabilità delle relazioni di potenza i cui coefficienti hanno, però, una notevole dipendenza dal sito di sperimentazione. In particolare le coppie portata-velocità ricadono generalmente all’interno della fascia individuata dalla relazione di Govers e da quella di Abrahams e non mostrano alcuna dipendenza dalla pendenza del rill. Le relazioni portata-larghezza sono contraddistinte da valori dell’esponente variabili tra 0.11 e 0.49 e frequentemente uguali al valore di letteratura pari a 0.3. Le coppie portata-larghezza sono, inoltre, influenzate dalla pendenza del rill e ai valori più elevati di s corrispondono le sezioni più strette. Le relazioni portata-tirante sono contraddistinte da valori dell’esponente variabili tra 0.22 e 0.65 e frequentemente pari al valore di letteratura pari a 0.4. Le coppie portata- tirante sono, inoltre, influenzate dalla pendenza del rill e ai valori più elevati di s corrispondono le sezioni con tiranti medi maggiori. Infine, le caratteristiche tessiturali dei suoli indagati hanno una limitata influenza sulla geometria idraulica dei rill.

The paper is a closure of “Stage-Discharge Relationship for an Unpstream Inclined Grid with Transversal Bars”

Nella memoria sono riportati i risultati delle verifiche di applicabilità di una tecnica image-based per il monitoraggio dei processi di erosione canalizzata. L’indagine, in particolare, ha avuto lo scopo di testare l’uso di modelli tridimensionali del terreno (DTM) ottenuti con l’impiego di un numero elevato di fotografie della stessa scena acquisite da differenti punti di vista (Tecnica “Structure-From Motion” SFM e “Multi-View-Stereo MVS). Il DTM tridimensionale (3D) è stato generato utilizzando il software open source Autodesk 123D Catch mentre per la creazione del Digital Elevation Model DEM (2.5D) è stato impiegato il software CloudCompare. Dei due canali in terra utilizzati nella sperimentazione, uno rettilineo a sezione triangolare e l’altro curvilineo a sezione trapezia, è stato effettuato anche il rilievo di alcune sezioni mediante un profilometro. Il volume effettivo di ciascun canale è stato misurato riempiendolo, dopo averlo impermeabilizzato con un film plastico, con un volume noto di acqua. Il confronto tra i tre metodi di rilievo (modello 3D, modello 2.5D e profilometro) ha evidenziato in tutti i casi una modesta sottostima del volume totale che per il caso del modello 3D assume il valore minimo pari allo -0.3% per il canale rettilineo e allo - 0.5% per quello curvilineo. Assunto come “riferimento” il modello 3D sono state confrontate le grandezze morfologiche e idrauliche relative alle sezioni di rilievo. Dall’analisi si evince che il profilometro fornisce valori della profondità massima, H, sistematicamente più alti rispetto a quelli del modello 3D, mentre il modello 2.5D non presenta differenze sistematiche in H rispetto al 3D. Il contorno bagnato viene sottostimato sia dal profilometro sia dal metodo 2.5D. I volumi dei singoli tratti, nel caso di canale curvilineo, risultano sistematicamente sottostimati (-0.73% per il modello 3D e –2.71% per il profilometro) come conseguenza della sottostima dell’area delle sezioni trasversali.

In order to measure soil loss in equipped plots the estimate of the weight of solid material intercepted at their lower end is required. At the experimental area of Sparacia, Sicily, the runoff produced by an erosive event is collected within storage tanks with a capacity of about 1m3. In this paper, the use of a new sampler is proposed to measure easily the weight of solid material eroded from an experimental plot and collected into a storage tank. The sampler is a cylinder having a closing valve at the bottom. Two different series of runs were carried out both to test the reliability of the sampler and to establish a sampling procedure, respectively. An analysis of various sampling configurations usable in the field differentiated by the number and location of sampling verticals in the tank cross-section was finally carried out. The results of the present investigation are that the concentration measurement by the sampler was more accurate than that obtained by other methods involving a collection tank, agitation and sampling of the suspension. This sampler is cheap and usable in combination with a quick field sampling procedure which is particularly advisable when the number of plots equipped at an experimental area is large. The sampler was tested using a clay soil contained within cylinders and a cubic tank, but it appeared also to be usable with coarser sediment than clay and in combination with tanks having a different shape.

Gully erosion represents one of the most significant types of land degradation in the Mediterranean areas, giving place to important on- and off-site effects. In this paper, a second-order gully located in SW Spain is analyzed. Along the gully, 28 cross-sections were established and measured with a Leica TCRM1102 laser total station, approximately every 6 months from 2001 to 2007. The sections were located at variable distance, placing them in areas where active erosion was evident. In total, 13 field measurements were carried out, and the geometric characteristics of 28 cross-sections were obtained. Morphometric analyses were carried out in both the main gully and a tributary reach by applying an empirical relationship between channel length and eroded volume. Morphometric variables of the gully sections were combined into two dimensionless groups, and a morphological similarity between different linear erosion landforms (rills, ephemeral and permanent gullies) was obtained. Then, the coefficient of variation of the calculated volumes was used to compare the instability between the main gully and the tributary reach. Finally, the hydraulic geometry of the gully was assessed by calibrating three empirical power equations, which relate bankfull discharge with mean flow velocity, cross-sectional depth and width. The hydraulic characterization of the main gully and the tributary reach was investigated for each field survey and a different behavior was detected. The hydraulic analysis also demonstrated that higher values of discharge provide better predictions of flow velocity; the size of the main and tributary gullies affects the discharge–width relationship; and that gully depth is the variable which can be predicted with the highest accuracy.

The main purpose of this booklet is to give to the participants to the Palermo’s Conference of the EU COST ACTION ES1306 - CONNECTING EUROPEAN CONNECTIVITY RESEARCH - CONNECTEUR a general idea of the scientific activity that was carried out in the past 20 years on the basis of the data collected at the Sparacia experimental station for soil erosion measurement, in Sicily, South Italy. The booklet includes a presentation of the experimental site, a description of the applied methods and procedures for measuring soil erosion processes at the Sparacia experimental area, and an illustration of the developed methodologies for predicting soil erosion from plots, small basins, rills and gullies. It is also included a chapter summarizing development of some regional tools that could be used by technicians and local authorities to make their choices on land management to preserve the soil resource. We wish express the feelings of our sincere gratitude to all friends and colleagues attending the meeting. We feel flattered by the presence of so many distinguished scientists and young and very promising researchers! We owe special thanks to Saskia Keesstra and Artemì Cerdà. They invited us to organize the meeting in Palermo and were always promptly and lovely present, helping us in many instances. Thanks Saskia and thanks Artemì from all of us!

Nella memoria sono riportati i risultati di un esperimento di simulazione della formazione del canale di un rill condotto in una parcella avente una dimensione 2x7 m2 ed una pendenza del 14% realizzata dal Dipartimento di Scienze Agrarie e Forestali dell’Università di Palermo. Una rete di solchi, costituita da due canali principali, è stata, dapprima incisa sul suolo manualmente e successivamente modellata utilizzando una corrente idrica limpida. Sui solchi modellati è stato effettuato, in corrispondenza di 11 sezioni trasversali della parcella, il rilievo delle caratteristiche geometriche e idrauliche utilizzando un profilometro. L’indagine ha inoltre previsto la realizzazione sia di un modello tridimensionale del terreno (DTM), ottenuto con l’impiego di un numero elevato di fotografie della stessa scena acquisite da differenti punti di vista, sia del modello 2.5D ad elevata risoluzione. I valori delle grandezze morfologiche e idrauliche, misurate con il profilometro ed estratte dal modello 2.5D, sono stati confrontati con quelli relativi al modello 3D assunto come “riferimento”. L’accuratezza conseguibile nella stima delle suddette grandezze è comparabile e si commettono errori generalmente minori del ± 10%. Sono state confrontate la relazione lunghezza L—volume V e quella dedotta teoricamente sulla base dell’analisi dimensionale, entrambe ottenute sulla base delle misure condotte con il profilometro e con i metodi 2.5D e 3D. Per il metodo 3D è stato inoltre valutato l’effetto dell’interdistanza tra le sezioni rilevate sulla relazione L-V. Infine, il modello 3D di uno dei canali principali è stato confrontato con il suo calco in gesso.

Numerosi risultati sperimentali hanno evidenziato che la perdita di suolo pluriennale di una parcella è influenzata apprezzabilmente dall’erosione che si verifica in un numero complessivamente limitato di eventi particolarmente gravosi. Conseguentemente, un intervento di conservazione del suolo calibrato sull’erosione media annua può risultare poco efficace in occasione degli eventi meteorici più significativi dal punto di vista dell’erosione complessiva. La disponibilità di modelli di previsione dell’erosione idrica parcellare in grado di fornire stime accurate dei valori più elevati della perdita di suolo alla scansione del singolo evento erosivo riveste pertanto interesse pratico, potendo contribuire a migliorare la scelta e il dimensionamento degli interventi anti-erosivi in un’area di interesse. Nella presente indagine, condotta con riferimento ai dati ottenuti nelle parcelle sperimentali di Sparacia, in Sicilia (lunghezza, λ = 11 – 44 m, pendenza, s = 14.9 – 26.0%), viene preliminarmente accertato che la perdita di suolo annua è dovuta a un numero ridotto di eventi e, in particolare, che i massimi annui determinano all’incirca il 75% dell’erosione complessiva. Viene quindi esaminata l’applicabilità dei modelli USLE e USLE-derivati per la previsione dei massimi annui della perdita di suolo per evento, calibrando ciascun modello con riferimento a questa particolare tipologia di eventi. L’analisi evidenzia la superiorità dell’approccio USLE-MM rispetto alla USLE e alla USLE-M. Con la USLE-MM, il fattore di erodibilità del suolo, assunto costante per l’intera area sperimentale, e l’espressione del fattore lunghezza della pendice non mostrano alcuna dipendenza significativa dalla tipologia di dati usati per la calibrazione (massimi annui, tutti gli eventi). I massimi annuali danno invece luogo a valori più elevati del fattore pendenza della pendice rispetto a quelli ottenuti considerando il complesso degli eventi. Le differenze tra i valori del suddetto fattore ottenuti con i due dataset crescono con la pendenza, assumendo un valore minimo del 17% per s = 14.9% e un massimo del 61% per s = 26.0%. Questo risultato segnala che l’effetto della pendenza sulla perdita di suolo è maggiore nel caso dei massimi annui rispetto a quello della totalità degli eventi, probabilmente in conseguenza della maggiore efficienza dei meccanismi di trasporto nel caso di eventi particolarmente gravosi.

Nella memoria sono riportati i risultati ottenuti a partire dalle distribuzioni dimensionali delle gocce di pioggia (DSD) rilevate nel periodo Luglio 2015- Gennaio 2016, mediante un disdrometro ottico installato presso la stazione sperimentale “El Teularet- Sierra de Enguera” sita nella comunità Valenciana. Dopo aver aggregato le DSD per classi di intensità, è stata condotta una analisi sulle caratteristiche delle distribuzioni rilevate in funzione dell’intensità di precipitazione ed è stata verificata l’applicabilità della distribuzione di Ulbrich utilizzando il metodo dei momenti per la stima dei parametri. Le misure sono state utilizzate per determinare i valori misurati di potenza cinetica associando le DSD alla velocità terminale delle gocce determinata mediante una relazione reperita in letteratura

At first, in this paper the stage-discharge relationship of a new flume, originally proposed by Samani and Magallanez, for measuring flow discharge in open channels is reviewed. The flume is obtained inserting two semicylinders in a rectangular cross-section. Then, the results of some experimental runs carried out using horizontal flumes characterized by different values of the contraction ratio (ranging from 0.17 to 0.81) are used for determining the two coefficients of the power stage-discharge equation. Finally, the stage-discharge equation is tested using flow measurements carried out, in the period December 2004 – March 2006 in the Sicilian experimental SPA1 and SPA2 basins. Field testing of the SMBF flume is developed using discharge measurements carried out by a Khafagi-Venturi flume placed in the field measurement channel of each experimental basin.

In this paper a spatially distributed model of the hillslope sediment delivery processes, named the sediment delivery distributed (SEDD) model, is initially reviewed; the model takes into account the sediment delivery processes due to both the hillslope sediment transport and the effects of slope curvature. Then the rainfall and sediment yield events measured at the experimental SPA2 basin, in Sicily, are used both to calibrate the SEDD model and to verify the predictive capability of the distributed sediment delivery approach at event scale. For the SPA2 basin discretized into morphological units and stream tubes, the SEDD model is calibrated at event scale using the measurements carried out at the outlet of the experimental basin in the period December 2000–January 2001. The model calibration is used to determine a relationship useful for estimating the unique coefficient βe of the model by rainfall erosivity factor Re at event scale. To test the predictive capability of the βe = f(Re) relationship, 20 events measured in the period September 2002–December 2005 are used; the comparison between measured sediment yield values and calculated ones for all monitored events shows that the sediment delivery distributed approach has a good predictive ability at event scale. The analysis also shows that estimating βe by the relationship βe = f(Re) gives a better agreement between measured and calculated sediment yields than obtained with the median value βe,m of all 27 calculated βe values. Finally the analysis at annual scale, for the period 2000–2005, allows the estimation of the median value βa,m representative of the annual behaviour. This analysis shows that the sediment delivery distributed approach also has a good predictive ability at annual scale. Copyright © 2006 John Wiley & Sons, Ltd.

Calanchi are a frequent type of badland landscape of Sicily (Italy), usually located in the middle of crops or forests. They are characterized by heavily dissected terrains with unvegetated slopes, knife ridge edges, V-shaped valleys and channels with a dendritic pattern, which incise and extend headwards. Calanchi exhibit, in smaller temporal and spatial scales, many of the geomorphic processes and landforms that may by observed in a fluvial landscape, hence, this type of badland may be considered as micro-watersheds where geomorphic dynamics can be related to their geometric features. The aim of this investigation was to evaluate the morphometric characteristics of calanchi landforms in Sicily (Italy). For this aim, DEMs obtained by LiDAR technology, with a horizontal and vertical resolutions of 2 m and 0.1-0.2 m, respectively, were used. In addition, orthophotographs with a pixel resolution of 0.25 m were exploited as a visual reference of the areas, as well as the images available on Google Earth. The morphometric characteristics were used to test two functional relationships: 1) an empirical relationship linking the volume of sediments eroded on a calanchi hydrographic unit to the total length of its main channel, and 2) a power relationship, established between two dimensionless groups of morphometric variables, that attests for a unique geometrical similarity condition between calanchi and smaller linear erosion landforms. Finally, the Hack’s law was tested demonstrating that the shape of calanchi units becomes wider with the increasing their drainage area. This result was also proved by the analysis of the maximum length and width of each landform, which showed that width increments slightly faster than length when increasing their size.

In this paper, experimental data collected in a straight flume having a bed covered by grasslike vegetation have been used to analyze flow resistance for flexible submerged elements. At first, the measurements are used to test the applicability of Kouwen’s method. Then, a calibration of two coefficients appearing in the semilogarithmic flow resistance equation is carried out. Finally, applying the P-theorem and the incomplete self-similarity condition, a flow resistance equation linking the friction factor with the shear Reynolds number, the depth-vegetation height ratio and the inflection degree is deduced.

A Closure to the paper “A new theoretical solution of the stage-discharge relationship for sharp-crested and broad weirs” is presented

Increasing concern for problems of soil degradation and the off-site impacts of accelerated erosion has generated a need for improved methods of estimating rates and patterns of soil erosion by water. The use of environmental radionuclides, particularly 137 Cs, to estimate erosion rates has attracted increased attention and the approach has been shown to possess several important advantages. However, the use of 137 Cs measurements to estimate erosion rates introduces one important uncertainty, namely, the need to employ a conversion model or relationship to convert the measured reduction in the 137 Cs inventory to an estimate of the erosion rate. There have been few attempts to validate these theoretical conversion models and the resulting erosion rate estimates. However, there is an important need for such validation, if the 137 Cs approach is to be more widely applied and reliance is to be placed on the results obtained. This paper reports the results of a study aimed at validating the use of two theoretical conversion models, namely the exponential depth distribution model and the diffusion and migration model, that have been used in several recent studies to convert measurements of 137 Cs inventories on uncultivated soils to estimates of soil erosion rates. The study is based on data assembled for two small catchments (1� 38 and 1� 65 ha) in Calabria, southern Italy, for which measurements of sediment output are available for the catchment outlet. The two catchments differ in terms of the steepness of their terrain, and this difference is reflected by their sediment yields. Because there is no evidence of significant deposition within the two catchments, sediment delivery ratios close to 1� 0 can be assumed. It is therefore possible to make a direct comparison between the estimates of the mean annual erosion rates within the two catchments derived from 137 Cs measurements and the measured sediment outputs. The results of the comparison show that the erosion rate estimates provided by both models are reasonably consistent with the measured sediment yields at the catchment outlets. However, more detailed assessment of the results shows that the validity of the erosion rate estimates is influenced by the magnitude of the erosion rates within the catchment. The exponential depth distribution model appears to perform better for the catchment with higher erosion rates and to overestimate erosion rates in the other catchment. Similarly, the basic migration and diffusion model performs better for the catchment with lower erosion rates and overestimates erosion rates in the other catchment. However, the improved migration and diffusion model appears to perform satisfactorily for both catchments. There is a need for further studies to extend such independent validation of the 137 Cs technique to other environments, including cultivated soils, and to other conversion models and procedures. Copyright # 2003 John Wiley & Sons, Ltd.

Velocity measurements carried out by an acoustic doppler velocimeter (ADV) in a rectangular laboratory flume having a gravel bed are presented. The velocity profiles are measured in six verticals of the channel cross-section having an increasing distance (from 4 to 38.5 cm) from the flume wall. The experimental runs are carried out for five different bed arrangements, characterized by different concentrations of coarser elements, and for the two conditions of small- and large-scale roughness. For both hydraulic conditions, the velocity measurements are first used to test the applicability of the Dean profile and of the logarithmic profile corrected by a divergence function proposed in this paper. Then, for each value of the depth sediment ratio h/d84, the non-dimensional friction factor parameter is calculated by integration of the measured velocity distributions in the different verticals of the cross-section. Finally a semi-logarithmic flow resistance equation is empirically deduced. © 2003 John Wiley and Sons, Ltd.

A previously published mixing length (ML) model for evaluating the Darcy–Weisbach friction factor for a large-scale roughness condition (depth to sediment height ratio ranging from 1 to 4) is briefly reviewed and modified (MML). Then the MML model and a modified drag (MD) model are experimentally tested using laboratory measurements carried out for gravel-bed channels and large-scale roughness condition. This analysis showed that the MML gives accurate estimates of the Darcy–Weisbach coefficient and for Froude number values greater than 0·5 the MML model coincides with the ML one. Testing of the MD model shows limited accuracy in estimating flow resistance. Finally, the MML and MD models are compared with the performance of a quasi-theoretical (QT) model deduced applying the P-theorem of the dimensional analysis and the incomplete self-similarity condition for the depth/sediment ratio and the Froude number. Using the experimental gravel-bed data to calibrate the QT model, a constant value of the exponent of the Froude number is determined while two relationships are proposed for estimating the scale factor and the exponent of the depth/sediment ratio. This indirect estimate procedure of the coefficients (b0, b1 and b2) of the QT model can produce a negligible overestimation or underestimation of the friction factor. Copyright © 2003 John Wiley & Sons, Ltd.

Improving empirical prediction of plot soil erosion at the event temporal scale has both scientific and practical importance. In this investigation, 492 runoff and soil loss data from plots of different length,  (11 <  < 44 m), and steepness, s (14.9 < s < 26.0%), established at the Sparacia experimental station, in Sicily, south Italy, were used to derive a new version of USLE-MM model, by only assuming a value of one for the topographic length, L, and steepness, S, factors for  = 22 m and s = 9%, respectively. An erosivity index equal to (QREI30)b1, QR and EI30 being the runoff coefficient and the event rainfall erosivity index, respectively, with b1 > 1 was found to be an appropriate choice for the Sparacia area. The specifically developed functions for L and S did not differ appreciably from other, more widely accepted relationships (maximum differences by a factor of 1.22 for L and 1.09 for S). The new version of the USLE-MM performed particularly well for highly erosive events, since predicted soil loss differed by not more than a factor of 1.19 from the measured soil loss for measured values of more than 100 Mg ha-1. The choice of the relationships to predict topographic effects on plot soil loss should not represent a point of particular concern in the application of the USLE-MM in other environments. However, tests of the empirical approach should be carried out in other experimental areas in an attempt to develop analytical tools, usable at the event temporal scale, reasonably simple and of wide validity.

In this paper a frequency analysis of event soil loss measurements collected in the period 1999–2012 at the microplots and plots of the Sparacia Experimental Area in Sicily, southern Italy, was developed. The analysis was carried out using the annual maximum soil loss measurements normalized by the mean soil loss measured at a given temporal and spatial scale. The empirical frequency distribution of the normalized variable was well fitted by two Gumbel’s theoretical probability distributions discriminated by a value of the normalized variable equal to 2. This last value discriminates between the relatively low and frequent values of the normalized variable and the high and rare ones. The annual maximum soil loss was demonstrated to be representative of the total annual soil erosion at the Sparacia Experimental Area. Then, a threshold soil loss value at the annual temporal scale was calculated by multiplying the frequency factor, equal to 2, by the mean annual maximum soil loss values for each given plot length. The value of the threshold soil loss decreased as the plot length increased. Finally, an analysis of occurrence of rilling was developed with regard both to the classical soil loss tolerance and the defined threshold soil loss. The conclusion that rilling can be limited using a threshold soil loss which is greater than the classical soil loss tolerance was drawn.

In this paper, the physical model concept by Nearing (1998. Catena 32: 15–22) was assessed. Soil loss data collected on plots of different widths (2–8 m), lengths (11–44 m) and steepnesses (14.9–26.0%), equipped in south and central Italy, were used. Differences in width between plots of given length and steepness determined a lower data correlation and more deviation of the fitted regression line from the identity one. A coefficient of determination between measured, M , and predicted, P , soil losses of 0.77 was representative of the best-case prediction scenario, according to Nearing (1998). The relative differences, Rdiff = ( P − M ) / ( P + M ), decreased in absolute value as M increased only for erosion rates approximately > 1 kg m − 2 . An alternative applicative criterion of the physical model concept, based on the | P − M | difference, was valid for the entire range of measured soil losses. In conclusion, the physical model should be defined in terms of perfect planimetrical equivalence. The best applicative criterion of the physical model concept may vary with the considered dataset, which practically implies the need to further test this concept with other datasets.

L'articolo riporta la risposta di chiusura alla discussione sull'articolo originale "New stage-discharge relationship for weirs of finite crest length"

Il misuratore a cilindri è un semplice strumento per la determinazione della portata idrica defluente in un canale rettangolare. Lo strumento è costituito da due semicilindri ad asse verticale posti in aderenza alle pareti del canale in modo da determinare un’ostruzione parziale al deflusso. La presenza del restringimento determina un rigurgito a monte dove la misura del tirante consente, mediante un’apposita relazione, di determinare la portata idrica. Nella memoria è presentata una verifica di campo del funzionamento del misuratore a cilindri sito nell’area sperimentale di Sparacia in Sicilia. Il misuratore è inserito in una canaletta a pendenza nulla di 12 cm di larghezza ed è caratterizzato da un rapporto di strozzamento pari a 0,5. A valle del misuratore a cilindri è posto un venturimetro per canali per la misura della portata defluente. I valori di tirante sono ottenuti mediante un misuratore di livello ad ultrasuoni. I rilievi, condotti con la scansione temporale del minuto, sono relativi al periodo Dicembre 2004 – Marzo 2012. La memoria riporta dapprima il confronto tra le suddette misure e la relazione proposta da Baiamonte e Ferro (2007), ottenuta mediante l’analisi dimensionale e l’approccio dell’autosimilitudine incompleta, mettendo in evidenza una sistematica sottostima delle portate e, di conseguenza, la necessità di una ricalibrazione. Successivamente è presentata una verifica della relazione proposta da Carollo et al. (2015), che trae origine dall’applicazione del teorema di Bernoulli tra la sezione a monte dello strumento e quella dove si instaura lo stato critico, nelle ipotesi di comportamento semimodulare del misuratore. In particolare, Carollo et al. (2015) hanno ipotizzato che, a causa della perdita di linearità della corrente, la sezione di controllo non coincide con la sezione ristretta ma, rispetto a questa, è spostata più a valle dove la corrente riacquista le caratteristiche di linearità. Secondo Carollo et al. (2015), rispetto alla sezione ristretta, la larghezza della sezione di controllo cresce con il rapporto tra il tirante idrico a monte e la larghezza della sezione ristretta. L’analisi delle misure di campo conferma la validità dell’approccio proposto da Carollo et al. (2015).

Molti modelli process-oriented per la previsione dell’erosione rill utilizzano parametri, come l’erodibilità rill, che sono specifici del sito di interesse e pertanto l’applicazione dei suddetti modelli necessita la misura di questi parametri o una loro stima indiretta. L’obiettivo del presente lavoro è quello di proporre un metodo per la misura indiretta dell’erodibilità rill del suolo dell’area sperimentale di Sparacia, in Sicilia. Sono state utilizzate le misure condotte sui rill rilevati nelle parcelle di Sparacia in occasione di sette eventi di pioggia naturale e un semplice approccio matematico basato sull’equazione che simula il distacco dei sedimenti tenendo conto della variabilità nel tempo delle variabili che vi compaiono. Il metodo proposto, la cui applicazione necessita soltanto la conoscenza delle caratteristiche geometriche dei rill alla fine dell’evento e della durata dell’evento, fornisce un valore approssimato dell’erodibilità rill poiché è basato su ipotesi semplificative. D’altra parte la misura dell’erodibilità rill in campo è più realistica, ma anche più complessa, di quella che si può ottenere con indagini di laboratorio e il metodo proposto presenta il vantaggio di semplificare la misura di campo.

Empirical prediction of soil erosion has both scientific and practical importance. This investigation tested USLE and USLE-based procedures to predict bare plot soil loss at the Sparacia area, in Sicily. Event soil loss per unit area, Ae, did not vary appreciably with plot length, l, because the decrease in runoff with l was offset by an increase in sediment concentration. Slope steepness, s, had a positive effective on Ae and this result was associated with a runoff coefficient that did not vary appreciably with s and a sediment concentration generally increasing with s. Plot steepness did not have a statistically detectable effect on the calculations of the soil erodibility factor of both the USLE, K, and the USLE-M, KUM, models but a soil-independent relationship between KUM and K was not found. The erosivity index of the USLE-MM model performed better than the erosivity index of the CSI (Central and Southern Italy) model. In conclusion, the importance of an approach allowing soil loss predictions that do not necessarily increase with l was confirmed together with the usability of already established and largely applied relationships to predict steepness effects. Soil erodibility has to be determined with reference to the specific mathematical scheme and conversion between different schemes seems to need taking into account the soil characteristics. The USLE-MM shows promise for further developments. The evolutionary concept applied in the development of the USLE should probably be rediscovered to improve development of soil erosion prediction tools.

La stima dell’erosione idrica mediante approcci empirici ha interesse sia scientifico sia applicativo. Nella presente indagine è stata condotta una verifica di ipotesi e procedure adottate nella USLE e in modelli basati sullo schema USLE per la stima della perdita di suolo da parcelle di suolo nudo nell’area sperimentale di Sparacia, in Sicilia. La perdita di suolo per unità di superficie del singolo evento erosivo, Ae, non è significativamente dipendente dalla lunghezza parcellare, λ, in quanto all’aumentare di λ si riduce il deflusso ma cresce la concentrazione dei sedimenti. I valori di Ae sono crescenti con la pendenza parcellare, s, in quanto il coefficiente di deflusso non varia apprezzabilmente con s mentre la concentrazione dei sedimenti generalmente cresce al crescere di s. In conclusione, l’indagine ha confermato l’importanza di un approccio che renda possibile la stima della perdita di suolo da parcelle in cui le asportazioni per unità di superficie non crescono necessariamente con la loro lunghezza. Le relazioni più largamente utilizzate per la determinazione dell’effetto della pendenza sull’erosione parcellare appaiono anche utilizzabili nell’area di Sparacia.

La USLE-MM è un modello previsionale della perdita di suolo alla scala dell’evento erosivo che introduce il coefficiente di deflusso parcellare nel set di variabili indipendenti della USLE e consente la previsione di una perdita di suolo per unità di superficie non necessariamente crescente con la lunghezza della pendice. Tale circostanza, che la USLE non è in grado di riprodurre, è stata ampiamente riscontrata in letteratura e nell’area sperimentale di Sparacia. Il fattore climatico della USLE-MM è pari ad una potenza del prodotto del coefficiente di deflusso per l’indice di aggressività della pioggia di Wischmeier e Smith (1978). Il modello USLE–MM è stato originariamente dedotto facendo uso delle equazioni utilizzate nella RUSLE per il calcolo del fattore lunghezza della pendice, L, e dell’equazione di Nearing (1997) per il calcolo del fattore pendenza della pendice, S. Un possibile limite del modello deriva dall’inadeguatezza delle suddette equazioni a descrivere l’effetto della lunghezza λ e della pendenza s della parcella sulla perdita di suolo. In una precedente memoria, con riferimento alle parcelle inclinate del 14,9%, nell’ipotesi che l’equazione di Nearing descriva accuratamente l’effetto della pendenza sulla perdita di suolo parcellare, erano stati determinati il fattore di erodibilità del modello, l’esponente b1 del fattore climatico e una relazione potenziale per la stima del fattore L specificatamente utilizzabile con il modello USLE–MM. La presente indagine ha l’obiettivo di testare se l’equazione di Nearing (1997) può essere efficacemente utilizzata nella USLEMM per stimare la perdita di suolo che si verifica su parcelle, installate nell’area di Sparacia, con pendenza maggiore di 14,9%. I valori del fattore pendenza della pendice della USLE-MM risultano più elevati di quelli calcolati con l’equazione di Nearing (1997) e le differenze percentuali aumentano al crescere di s.

La previsione dell’erosione idrica alla scala temporale del singolo evento riveste particolare interesse dal momento che la perdita di suolo complessiva di un periodo pluriennale è generalmente determinata dagli eventi più rilevanti. Recentemente, utilizzando le misure di perdita di suolo ottenute su parcelle nude installate in tre stazioni sperimentali italiane (Sparacia, in Sicilia; Masse, in Umbria; Caratozzolo, in Calabria), è stato sviluppato un modello empirico, denominato CSI (Central and Southern Italy), per la stima della perdita di suolo alla scala dell’evento. La presente memoria riporta i risultati della verifica di applicabilità del suddetto modello che è stata condotta utilizzando il complesso delle misure ad oggi disponibili per le tre stazioni sperimentali. Il modello è stato corretto per tenere conto della influenza residua della pendenza parcellare sulla stima della perdita di suolo che era stata precedentemente trascurata. La correzione apportata non ha modificato la struttura matematica originaria del modello. Infine, il modello è stato ricalibrato massimizzando l’indice di Nash-Sutcliffe calcolato sul complesso dei dati a disposizione.

The study of the detachment of soil particles due to rainfall erosivity requires knowledge of the energetic characteristics of the precipitation. In this paper, following a review of both the drop-size distribution (DSD) proposed by one researcher and the corresponding relationship for evaluating the kinetic power of rainfall, the reliability of that researcher’s DSD using the size distributions of raindrops detected by an optical disdrometer installed at Palermo (Sicily) is experimentally tested. Finally, an experimental verification of both the relationship proposed by two separate research teams for evaluating the specific and unit rainfall kinetic energy is carried out.

Understanding of the hydraulics of flow over vegetation is very important to support the management of fluvial processes. In this paper the flow over flexible bottom vegetation is experimentally studied. A two-dimensional-acoustic doppler velocimeter is used to measure the local flow velocities for different vegetation concentrations, discharges, and flume slopes. The influence of vegetation concentration and the depth/vegetation height ratio on the measured velocity profiles is analyzed. All measured velocity distributions are S-shaped and exhibit a three-zone profile. The relationship between the velocity distribution and the turbulence intensity distribution is also analyzed. The characteristics ~inflection point, maximum value, asymptotes ! of the measured velocity distributions and the results of the previous investigators are used to select an analytical expression for the shape of the velocity profile. A theoretical velocity profile is deduced using the classical Prandtl's mixing length approach with a new expression for the mixing length. The deduced four-coefficient profile allows description of the flow both inside and above the vegetation. The physical and geometrical meaning of the four coefficients are also shown. DOI: 10.1061/~ASCE!0733-9429~2002!128:7~664! CE Database keywords: Velocity profile; Vegetation; Channel flow.

Rills evolve morphologically, and the adjustment of rill channel geometry to flow affects the relationships among velocity, discharge, and slope. The resistance to flow in step-pool rills is mainly due to form-induced mechanisms and, in comparison, grain resistance is of minor significance. Previous studies on rill flow resistance have been performed exclusively for grainresistance conditions and use a stream flow equation. In this study, a new flow resistance equation, deduced by applying dimensional analysis and self-similarity theory, was applied to rill flow in step-pool channels. First, the incomplete self-similarity hypothesis was used for establishing a power flow velocity profile whose integration gives the theoretical expression of the Darcy-Weisbach friction factor. Then the deduced theoretical resistance equation was tested by measurements of flow velocity, water depth, channel width, and bed slope performed in 49 reaches of some rills having a step-pool bed. A relationship between the velocity profile, the channel slope, and the flow Froude number was established. The analysis showed that the Darcy-Weisbach friction factor can be accurately estimated by the proposed theoretical approach based on a power-velocity profile. The Darcy-Weisbach friction factor values related to rills with step-pool sequences, on average, are higher than those related to rills without step pools, signifying that rills where step-pool sequences occur are characterized by a total resistance (grain and morphological) that is higher than grain resistance. Finally, this investigation showed that step pools that maximize flow resistance may develop at Froude numbers below the range at which step pools may form as antidunes.

In this short communication the four estimate criteria of the depth-averaged local velocity proposed by Byrd et al. (Earth Surface Processes and Landforms, 2000, Vol. 25, pp. 167-173) are compared both with the three-point method of Bathurst and with the average velocity obtained by integrating the velocity profile (FPa2) suggested by Ferro and Pecoraro (Water Resources Research, 2000, vol. 36, pp. 2761-2770). The comparison was carried out using 84 velocity profiles measured by an acoustic Doppler velocimeter in a rectangular flume with a gravel bed. Copyright © 2002 John Wiley and Sons, Ltd.

The discusser would like to thank the authors of the original paper for investigating the outflow process of an upstream inclined grid with longitudinal bars using the dimensional analysis and the incomplete self-similarity theory. The discusser, however, would like to add a few points. Using the theoretical analysis the authors of the original paper showed that a power equation can be used for establishing the stage-discharge equation of an upstream inclined grid with longitudinal bars. The authors of the original paper also showed that the coefficient and exponent of the power equation depend on the slope angle and the void ratio. They proposed a stage-discharge equation

Recent concern for problems of soil degradation and the offsite impacts of accelerated erosion has highlighted the need for improved methods of estimating rates and patterns of soil erosion by water. The use of environmental radionuclides, particularly caesium-137 (137Cs), as a means of estimating rates of soil erosion and deposition is attracting increasing attention and the approach has now been recognised as possessing several important advantages. However, one important uncertainty associated with the use of 137Cs measurements to estimate soil erosion rates is the need to employ a calibration relationship to convert the measured 137Cs inventory to an estimate of the erosion rate. Existing calibration procedures are commonly subdivided into empirical relationships, based on independent measurements of soil loss, and theoretical models, that make use of existing understanding of the fate and behaviour of fallout radionuclides in eroding soils to derive a relationship between erosion rate and the reduction in the 137Cs inventory relative to the local reference value. There have been few attempts to validate these theoretical calibration models and there is an important need for such validation if the 137Cs approach is to be more widely applied. This paper reports the results of a study aimed at validating the use of a simple exponential profile distribution model to convert measurements of 137Cs inventories on uncultivated soils to estimates of soil erosion rates. It is based on a small (1.38 ha) catchment in Calabria, southern Italy, for which measurements of sediment output are available for the catchment outlet. Because there is no evidence of significant deposition within the catchment, a sediment delivery ratio close to 1.0 can be assumed. It is therefore possible to make a direct comparison between the estimate of the mean annual erosion rate within the catchment derived from 137Cs measurements and the measured sediment output. In undertaking this comparison, account was taken of the different periods covered by the measured sediment output and the erosion rate estimated using 137Cs measurements. The results of the comparison show close agreement between the estimated and the measured erosion rates and therefore provide an effective validation of the use of the 137Cs approach and, more particularly, a profile distribution calibration model, to estimate soil erosion rates in this small catchment. Further studies are required to extend such independent validation to other environments, including cultivated soils, and to different calibration procedures. © 2001 Elsevier Science B.V.

La ricerca, finanziata da Il Sole Onlus, ha valutato l’efficacia di un intervento di supporto psicopedagogico, counselling e recupero sociale per bambine etiopi vittime di violenza sessuale. In Etiopia i bambini vittime di violenze riportano scarso supporto sociale, bassa autostima e pensieri intrusivi. 19 bambine (eta media 9.7 anni), vittime di violenza sessuale, hanno partecipato all’intervento. Si e valutato nelle bambine all’inizio e 12 mesi dopo l’intervento il PTSD, il rischio depressivo, i problemi comportamentali e i comportamenti sessualizzati. Dopo un anno di intervento si e verificata la diminuzione di: rabbia, sintomi post-traumatici, problemi internalizzanti ed esternalizzanti, depressione, problemi sociali, di attenzione e pensiero, e comportamento aggressivo. La riduzione di tali problematiche indicano l’efficacia dell’intervento.

Three-dimensional photo-reconstruction methods based on Structure from Motion (SfM) and MultiView-Stereo techniques (MVS) are tested for measuring, monitoring and quantifying three different geomorphological features: i) the Corral del Veleta rock glacier and ii) five small gully headcuts in Spain and iii) Calanchi type badland in Italy. Results about the accuracy, usefulness and applicability of these techniques are presented here. The results of these analyses showed centimeter-level accuracies with average distances to the benchmark models ranging from 0.009 m to 0.42 m.