1,720,979 research outputs found
Manuale tecnico-operativo per la modellazione e la valutazione dell’integrità dell’habitat fluviale
Full text linkIl presente Manuale descrive la modellazione e la valutazione dell’integrità dell’habitat fluviale utilizzando l’approccio a meso-scala e la metodologia denominata “MesoHABSIM – Mesohabitat Simulation Model”. Tale metodologia, adattata per il contesto italiano, si inserisce nel più ampio “Sistema di Valutazione Idromorfologica, Analsi e Monitoraggio dei corsi d’acqua – IDRAIM” (ISPRA, MLG N° 131/2016). In particolare, la metodologia MesoHABSIM è integrata con il “Sistema di Rilevamento e Classificazione delle Unità Morfologiche dei corsi d’acqua – SUM” (ISPRA, MLG N° 132/2016) per costituire uno strumento atto a descrivere la variabilità spazio-temporale degli habitat fluviali disponibili per la fauna, in funzione della portata defluente e della morfologia del corso d’acqua. La metodologia descritta nel presente manuale è inoltre in accordo con quanto riportato nelle linee guida in tema di “ecological flows” (e-flows) dell’Unione Europea (“Ecological flows in the implementation of the Water Framework Directive”, European Commission, Guidance N° 31, 2015), in cui viene menzionata come strumento idoneo alla valutazione dell’habitat fluviale e utilizzata in due casi studio (casi studio #6 e #8 della guida). Viene infine presentato nel manuale l’Indice di integrità dell’Habitat (IH) e riportati i passi procedurali per la sua applicazione
Defining minimum environmental flows at regional scale: application of mesoscale habitat models and catchments classification
No full textIn the context of water resources planning, this work defined a possible approach to quantify minimum environmental flows (e-flows) at a regional scale. Focusing on catchments smaller than 50km2, the problem was addressed through mesoscale habitat models and a catchment classification technique (regression tree algorithm). Within the Piedmont region in NW Italy, 25 reference streams were chosen on the basis of the natural condition of the flow regime and fish community. Mesohabitats were sampled for hydromorphic and fish parameters following the mesoscale habitat models approach. Logistic regression models, along with 55 habitat descriptors, were then used to build multivariate habitat suitability criteria, identifying the habitat characteristics mostly used by the target fish species. These models were applied to each stream reach and used to classify each mesohabitat into suitability categories. The reference minimum discharge for each stream was derived from habitat-flow rating curves. Finally, to define the regional criteria, the study domain was split according to the regression tree classification, defining homogenous sub-regions distinct on both e-flows and catchment/stream characteristics. This bottom-up approach used a catchment classification technique based on the environmental requirements of the fish communities and demonstrated potentials for further applications to defining e-flows at regional scale
La modellazione a meso-scala per la valutazione e quantificazione dell'habitat in torrenti e fiumi alpini
No full textHabitat modeling in high gradient streams: the meso-scale approach and application
No full textThe study aims to set out a new methodology for habitat modeling in high gradient streams. The methodology is based on the meso-scale approach of the MesoHABSIM simulation system and can support the definition and assessment of environmental flow and habitat restoration measures. Data coming from 40 study sites located within the mountainous areas of the Valle d'Aosta, Piemonte and Liguria regions (NW Italy) are used in the analysis. To adapt MesoHABSIM to high gradient streams, we first modified the data collection strategy to address the challenging conditions of surveys by using GIS and mobile mapping techniques. Secondly, we built the habitat suitability models at a regional scale to enable their transferability among different streams with different morphologies. Thirdly, due to the absence of stream gauges in headwaters, we proposed a possible way to simulate flow time series and, therefore, generate habitat time series. The resulting method is evaluated in terms of time expenditure for field data collection and habitat modeling potentials, and it represents a specific improvement of the MesoHABSIM system for habitat modelling in high gradient streams, where other commonly used methodologies can be unsuitable. Through its application in several study sites, the proposed methodology adapts well to high gradient streams and allows: (1) definition of fish habitat requirements for many streams simultaneously, (2) modeling of habitat variation over a range of discharges, and (3) determination of environmental standards for mountainous watercourses
Meso-scale habitat models for the mitigation of hydro-power impacts in high gradient streams
No full textModelling habitat requirements of bullhead (Cottus gobio) in Alpine streams
No full textIn the context of water resources planning and management, the prediction of fish distribution related to habitat characteristics is fundamental for the definition of environmental flows and habitat restoration measures. In particular, threatened and endemic fish species should be the targets of biodiversity safeguard and wildlife conservation actions. The recently developed meso-scale habitat model (MesoHABSIM) can provide solutions in this sense by using multivariate statistical techniques to predict fish species distribution and to define habitat suitability criteria. In this research, Random Forests (RF) and Logistic Regressions (LR) models were used to predict the distribution of bullhead (Cottus gobio) as a function of habitat conditions. In ten reference streams of the Alps (NW Italy), 95 mesohabitats were sampled for hydro-morphologic and biological parameters, and RF and LR were used to distinguish between absence/presence and presence/abundance of fish. The obtained models were compared on the basis of their performances (model accuracy, sensitivity, specificity, Cohen's kappa and area under ROC curve). Results indicate that RF outperformed LR, for both absence/presence (RF: 84 % accuracy, k = 0.58 and AUC = 0.88; LR: 78 % accuracy, k = 0.54 and AUC = 0.85) and presence/abundance models (RF: 79 % accuracy, k = 0.57 and AUC = 0.87; LR: 69 % accuracy, k = 0.43 and AUC = 0.81). The most important variables, selected in each model, are discussed and compared to the available literature. Lastly, results from models' application in regulated sites are presented to show the possible use of RF in predicting habitat availability for fish in Alpine stream
Implementation of the Natural Flow Paradigm to Protect Dwarf Wedgemussel (Alasmidonta heterodon) in the Upper Delaware River
Full text linkThis paper demonstrates the use of a multiplex habitat model for flow management criteria development compliant with the natural flow paradigm using the Upper Delaware River (NY/PA—USA) as an example. The goal of this study was to identify strategies to protect and support the recovery of the dwarf wedgemussel populations in the mainstem Delaware River. We quantified potential habitat, developed instreamflow recovery scenarios and modelled the scenario outcomes. Mesohabitat simulation model and River2D have been used to allow the transfer of suitability criteria between scales. Habitat time series were investigated with the help of the uniform continuous under threshold technique to establish natural habitat stressor thresholds. Exceedance of persistent and catastrophic durations results in habitat stress days (HSD). HSD served as a metric for the comparison of four flow and two habitat management scenarios. The greatest habitat improvements were accomplished through increasing the boundary Reynolds number, hence increasing the river bed diversity. The introduction of naturalized flows into the model did not cause any significant reduction of HSD, demonstrating that optimizing suitable habitat for dwarf wedgemussel may not be achieved without including morphological improvements. Both minimum and pulsed flow augmentation strategies were found to nullify rare stress days in our models. Our study found that, at a minimum, a pulsed flow regime would need to be created to promote the development of populations beyond the current mussel beds. To accomplish protection and enhancement of habitat fully, channel improvements that reduce boundary Reynolds number appear necessary. These recommendations are intended to create a starting point in the adaptive flow management process for the Upper Delaware River. Copyright © 2016 John Wiley & Sons, Ltd
Use of quantitative habitat models for establishing performance metrics in river restoration planning
No full textThe ecological effectiveness and success of river restoration strongly depends on the resources invested in planning. Unfortunately, this trend of restoration engineering is frequently compromised by the application of qualitative assessment and resource intensive adaptive management processes. Habitat simulation models are effective tools for selecting ecologically effective restoration measures as part of the Environmental Benefits Analysis. Through the support from a mesohabitat simulation model (MesoHABSIM), we identified three habitat metrics: 1) Habitat Quantity Deficiency (HQD), 2) Alteration of Habitat Structure (AHS), and 3) Habitat Stress Days Alteration (HSDA) to quantify and visualize differences between restoration options in Restoration Alternatives Assessment (RAA) diagram. This concept of quantifying habitat models is supported by an example of application in the Wekepeke Brook in Massachusetts, in which the habitat metrics were used to define quantitative benchmarks, goals and targets to guide the restoration process from the design to the evaluation phase. The three habitat metrics are a cost effective alternative for evaluating the ecological benefits of a planned action. The methodology contributes to a high potential for designing and monitoring restoration project
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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