1,721,019 research outputs found
Distributed Process-Based Hydrological Modeling of Urban Catchments with Nature-based Solutions
No full textUrbanization and climate change pose significant challenges for urban water systems, particularly in northern regions where seasonal snowmelt, rain-on-snow events, and variable infiltration conditions increase flood risks. This study evaluates the new distributed, physics-based STYX model developed by Technical Research Centre of Finland (VTT) for simulating surface runoff, infiltration, and stormwater flows in urban catchments. STYX provides enhanced spatial resolution compared to conventional models like EPA's Storm Water Management Model (SWMM) by resolving processes at the grid-cell level, enabling dynamic interactions between surface, subsurface, and stormwater networks.The model was tested in the Vallikallio catchment in Finland using high-resolution meteorological, land-use, and soil data. Results from the calibration and validation periods indicate that STYX effectively captures spatial hydrological variability, with a Nash-Sutcliffe Efficiency (NSE) of 0.71 in calibration and 0.71 in validation, comparable to the calibrated SWMM (NSE = 0.75 in calibration, 0.78 in validation). While both models underestimated peak discharges, STYX provided a more detailed representation of hydrological interactions, including infiltration dynamics and evapotranspiration partitioning.A key advantage of STYX is its ability to simulate bidirectional flows and backwater effects, which are critical for assessing urban flood risks and the effectiveness of nature-based solutions (NBS). The model also distinguishes between evaporation and transpiration components, allowing for a more detailed evaluation of water balance dynamics. Sensitivity analysis highlighted that land cover properties, particularly Manning’s roughness for roads and buildings, as well as soil hydraulic parameters, had the strongest influence on simulated discharges. The model’s ability to capture spatially distributed infiltration patterns emphasizes the importance of accurate soil parameterization, particularly in regions where infiltration potential varies significantly due to shallow soils and heterogeneous land cover.Despite these strengths, STYX remains computationally demanding, with a runtime of 137 seconds for the calibration period compared to a few seconds in SWMM. However, this cost is offset by its enhanced capability to represent detailed hydrological processes, making it a valuable tool for urban planners and hydrologists assessing NBS for flood mitigation and climate adaptation. The findings suggest that STYX is particularly well-suited for applications requiring high spatial granularity, such as evaluating the effectiveness of green infrastructure interventions.Future research will focus on extending simulation periods to assess long-term hydrological trends, refining soil depth representations to improve infiltration modeling, and integrating Nordic-specific processes such as ground frost and seasonal snowmelt. The incorporation of automated mesh generation and parameterization methods will also enhance the model’s usability for broader urban hydrological applications. Ultimately, STYX offers a flexible and detailed framework for simulating complex urban hydrological interactions, contributing to more resilient urban water management strategies in a changing climate
Modelling water flow and soil erosion in clayey, subsurface drained agricultural fields
Get PDFSoil erosion in clayey, subsurface drained agricultural fields in Finland can cause problems due to the export of suspended sediment and sediment-bound nutrients into nearby waterways. Suspended sediment is transported from the field via two main hydrological pathways: 1) surface runoff and 2) preferential flow in macropores to subsurface drains. In clayey fields especially, the sediment load via the subsurface drains can be a considerable part of the annual load. The mechanisms contributing to the sediment load during the growing season and the following autumn were quantified with a new numerical model (FLUSH) developed in the study, using sample data from two clayey, subsurface drained field sections in southern Finland.
The simulated field was computationally divided into two-dimensional overland and three-dimensional subsurface domains. Existing mechanistic approaches were applied to describe both surface and subsurface domain processes in the model. A dual-permeability model can simultaneously simulate flow in both soil matrix and macropore systems. The model supports simulation of suspended sediment transport in macropores, drainage systems, soil swelling and shrinkage processes and the effects of cropping and tillage operations on water and sediment yields. A new pentadiagonal matrix algorithm-based solution was developed to directly solve subsurface flow in both pore systems. A custom time integration method was derived to run the solution algorithms with different time steps in concurrent fashion. All the finite volume-based partial differential equation solution algorithms were parallelised with the OpenMP application interface. Computational grids, created with an automatic grid generation system, were used to test the effects of grid resolution on results.
The numerical model successfully described water flow and soil erosion in the study fields indicating that the hypothesised mechanisms for water flow and soil erosion were appropriate. The simulation results confirmed that preferential flow has a profound impact on field-scale hydrology. Runoff distribution between surface runoff and drainflow changed in the autumn due to tillage operations and soil swelling. Soil erosivity also increased after autumn tillage. In the simulations, hydraulic erosion was the primary process leading to high erosion rates in the Sjökulla field. In the Hovi field, lack of surface runoff notably lowered the sediment loads. Simulations with 1-D and 2-D grids indicated that the application of a 3-D model to undulating, clayey, subsurface drained fields was well justified. Tests with spatial variation of macroporosity presented evidence that the spatial variability of soil properties has a notable effect on runoff and sediment loads
Metsäteollisuuden energiatuotannossa syntyvän tuhkan hyötykäyttö: haitallisten asineiden kulkeutuminen
No full textSuomen metsäteollisuuden energiantuotannossa syntyy vuosittain noin 350 000 tonnia maa- ja ympäristörakentamisessa hyödyntämiskelpoista lentotuhkaa.
Lähitulevaisuudessa logistiikka- ja varastokustannukset tulevat kasvamaan edelleen ympäristölainsäädännön kiristyessä.
Tuhkan uusiokäyttöastetta pitäisi kasvattaa edelleen, jotta kulut pysyisivät alhaalla.
Suurin hyötykäyttöpotentiaali tuhkalle muodostuu sen käytöstä luonnon kiviainesta korvaavana materiaalina erilaisissa rakennuskohteissa.
Metsäteollisuus ry:n koordinoimassa hankkeessa tutkittiin tierakenteen sisällä käytetyn lentotuhkan ympäristövaikutuksia.
Tuhkasta liukenee veteen aineita kuten fluoridia, kloridia, molybdeenia, seleeniä ja sulfaattia.
Aineet kulkeutuvat veden mukana ympäristöön nostaen maa- ja pohjaveden pitoisuuksia.
Suurina pitoisuuksina monet tuhkan aineista ovat terveysriski lähiseudun ihmisille ja eläimille.
Aineiden kulkeutumista tierakenteista ympäristöön tutkittiin työtä varten ohjelmoiduilla numeerisilla laskentamalleilla.
Laskentamallien avulla työssä voitiin tutkia moninkertainen määrä tilanteita empiiriseen mittaamiseen verrattuna ja seuloa tuloksista kulkeutumiseen vaikuttavat päätekijät.
Vesien virtausta kuvattiin Richardsin yhtälöön perustuvalla ratkaisulla.
Aineiden kulkeutumismallissa otettiin huomioon advektio, dispersio sekä aineiden pidättyminen maahan.
Aineiden kulkeutumista tutkittiin tierakenneprototyypeillä, joihin sijoitettiin tutkittavat tuhkamäärät.
Teiden päällysteitä simuloitiin imeynnän määrän avulla.
Päällystetyn asfalttitien läpi imeytyvä vesimäärä oli kaksi tai kolme kertaa pienempi kuin peitetyn eli pintastabiloidun hiekkatien.
Pitoisuuksia seurattiin tierakenteen vieressä olevassa kaltevassa rinteessä ja niitä verrattiin Sosiaali- ja terveysministeriön asetukseen talousveden laatuvaatimuksista.
Tuhkasta liukenevaan ainemäärään vaikutti tutkitun tierakenteen leveys, tuhkarakenteen paksuus, liukenevan aineen määrä tuhkassa ja tiepäällysteen läpi imeytyvä vesimäärä.
Pitoisuusrintaman etenemiseen maassa vaikuttivat imeyntämäärän lisäksi maan vedenjohtavuus, rinteen kaltevuus, vettä johtavan maaprofiilin paksuus ja aineen kemialliset ominaisuudet.
Suurimmat pitoisuudet suhteessa aineiden raja-arvoihin syntyivät sulfaatista ja fluoridista.
Päällystetyillä rakenteilla pitoisuusrajat ylitettiin suurimmilla tuhkamäärillä ja rinteen kaltevuuksilla.
Peitetyillä rakenteilla pitoisuusrajat ylitettiin kaikilla suurimmilla tuhkarakenteilla kaltevuusarvosta riippumatta
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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