Gabriella Balacco

Improving the ANN Classification Accuracy of Landsat Data Through Spectral Indices and Linear Transformations (PCA and TCT) Aimed at LU/LC Monitoring of a River Basin

In this paper an efficient Artificial Neural Networks (ANN) classification method based on LANDSAT satellite data is proposed, studying the Cervaro river basin area (Foggia, Italy). LANDSAT imagery acquisition dates of 1984, 2003, 2009 and 2011 were selected to produce Land Use/Land Cover (LULC) maps to cover a time trend of 28 years. Land cover categories were chosen with the aim of characterizing land use according to the level of surface imperviousness. Nine synthetic bands from the PC, Tasseled Cap (TC), Brightness Temperature (BT) and vegetation indices (Leaf area Index LAI and the Modified Soil Adjusted Vegetation Index MSAVI) were identified as the most effective for the classification procedure. The advantages in using the ANN approach were confirmed without requiring a priori knowledge on the distribution model of input data. The results quantify land cover change patterns in the river basin area under study and demonstrate the potential of multitemporal LANDSAT data to provide an accurate and cost effective means to map and analyze land cover changes over time that can be used as input for subsequent hydrological and planning analysis.

Experimental analysis of air valve behaviour during hydraulic transients

The dynamic behaviour of air valves is still, to date, not very well known and, despite numerous scientific contributions, a standard approach for their dimensioning is yet to be found. Several analytical and experimental laboratory studies have been conducted for rapid pressurizing of entrapped air in a pipeline system, but most of these analyses have been performed with an air valve located at the end of a horizontal pipeline. In this study, an experimental analysis is carried out for several orifice sizes installed on a viscoelastic pipe for different boundary conditions. A brief description of the experimental hydraulic circuit and test procedures is provided, presenting the results of this laboratory experience. Experimental results show that the overpressure, due to entrapped air in a pressurized system, may depend on several factors such as pipeline slope.

An object-based method for mapping ephemeral river areas from WorldView-2 satellite data

Continuous monitoring of river basins has become a significant requirement of our times. Due to increasing water scarcity and unprecedented flood calamities, assessing existing water resources and gathering timely information on water increase are nowadays essential to develop suitable strategies in water resources management. Hydrological models are being studied to increase hydrological process understanding and to support decision making in this field. River basin management models typically operate on wide territories and, given the complexity of most river basins, they are based on semi-empirical lumped parameterizations of hydrological processes. To overcome the uncertainties inherent in such models and achieve acceptable model performance, calibration techniques are indispensable. Remote sensing and satellite-based data with high temporal resolution have the potential to fill such critical information gaps. With its nine spectral bands and very high resolutions (spectral and radiometric) WorldView-2 satellite sensor (WV-2) can provide new insights in the on-going debate comparing object-oriented and spectral-based classifications for the highest accuracy. This paper proposes an efficient object-based method for land cover mapping from Worldview-2 imagery in order to assess its potentiality in acquiring detailed basic information on an ephemeral river area (Lama di Castellaneta, Taranto, Italy), to support further studies in the field of hydrological processes modeling. The approach suggested was evaluated by estimating classification accuracy.

Mass transport triggered by heavy rainfall: the role of endorheic basins and epikarst in a regional karst aquifer

This study aims at recognizing the mechanisms of mass transport between the karst surface and the saturated zone in a morpho-structural relief of the Mesozoic karst carbonate platform of Murgia (Puglia, Southern Italy). The large dimension of the karst aquifer, the regional scale of the flow system, the boundary condition constituted by the sea, and the lack of freshwater springs constrain to the use of wells as monitoring points and limit the study area to the recharge area comprising 986 endorheic basins. The concentrations of non-reactive tracers (nitrates) in the waters of autogenic recharge (from endorheic basins) have been modelled through the evaluation of effective infiltration, land use, and nitrogen surplus, with reference to a time window, which includes a low precipitation period followed by significant rainfall events. The comparison between the modelled nitrate concentrations and the nitrate concentrations measured in ground waters, coupled with the analysis of groundwater chemograms and records of hydraulic heads (all referred to the same time window), allows inferring the mechanism of mass transport between the karst surface and the groundwater table. The mass transport conceptual model requires the presence of the epikarst. The infiltration of significant rainfall in the endorheic basins after a low precipitation period displaces waters stored in the epikarst towards the saturated zone. Ground waters in the post-evet period show higher concentrations of nitrates, lower concentrations of Total Organic Carbon and higher Mg/Ca ratios than both those of the pre-event period and the autumn-winter recharge period. The post-event recharge from epikarst storage determines a transient hazard of groundwater pollution with a time lag from the occurrence of the heavy rainfall.

The interrill erosion for a sandy loam soil

Abstract This paper resumes a laboratory experience on a slope adjustable plot with the aim of examining the role of rainfall intensity and slope gradient for a sandy loam soil, typical of Southern Italy, with particular initial moisture content. The results of the simulations performed show that a rainfall reduction causes a corresponding percentage reduction of sediment output. A similar behaviour can be attributed to slope gradient, while runoff moderately increases with rainfall intensity but it is not sensitive to slope gradient. Data also highlight that the degree of saturation can affect runoff and soil loss values.

Flood Susceptibility Evaluation on Ephemeral Streams of Southern Italy: A Case Study of Lama Balice.

In the proposed work areas exposed to flood risk were evaluated in a particular context of karst ephemeral streams located in Puglia region (Southern Italy). The case study of Lama Balice, characterized by a natural geomorphologic structure, was tested for the application of a DTM-based approach, aimed to the rapid identification and mapping of flood risk. The inundated areas, obtained with a 2D hydraulic model, following design rainfall events characterized by different return periods, were used as reference maps for the selection of the most appropriate geomorphological descriptor exploiting the binary classifiers test. The performance of the adopted procedure was tested by validating the selected geomorphological descriptors on a different area with respect to that used for calibration, in order to estimate the discrepancy between DTM-based flood maps and those obtained by numerical simulation.

Investigation of a Flood Event Occurred on Lama Balice, in the Context of Hazard Map Evaluation in Karstic-Ephemeral Streams

In the context of flood risk assessment and urban territory protection, the proposed research is focused on the definition of flood hazard maps by using high-resolution Digital Terrain Models (DTMs) obtained by a Light Detection And Ranging [LiDAR], remote sensing technique. The hydrologic/hydraulic model was calibrated on a flood event occurred on June 2014 on Lama Balice, ephemeral stream located in Puglia (Southern Italy), using the water levels observed during field campaign. In particular the analysis was performed for the definition of hazard maps with return periods of 30, 200 and 500 years, exploiting a combined scheme of a mono/two dimensional flood propagation approach for the delineation of flooded areas. The conducted research gives a significant contribution for the assessment of techniques of dynamic hazard and risk evaluation, in order to support institutions (like Basin Authorities and Civil Protection agencies) and professionals, in the context of the application of recent European legislation on flood risk protection (Floods Directive 2007/60/EC) and for European programs of scientific research (as Horizon 2020) in ungauged karstic catchment.

Flood Hazard Assessment of the Fortore River Downstream the Occhito Dam, in Southern Italy

In recent decades the effects generated by human activity that have led to the reduction of the natural water retention capacity of the soil and those generated by climatic factors rapidly changing, have exacerbated the hydrogeological instability and amplified the national territory vulnerability. Despite the flood risk in Italy is a topic of great interest, there are several aspects, especially in the management of flood events, that require further investigation; examples are floods caused by dam discharge. In this paper the distribution of hazard areas in downstream of Occhito Dam, has been carried out. Several hazard scenarios were considered related to only dam discharge or relating to the simultaneous presence of the dam contribution and contributions from river basins downstream of the Occhito dam. The results, validated using flooding photo, are presented and discussed, providing flow-rate in order to predict potential floods.