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  • 1. Bandeira, Jefferson Vianna
    et al.
    Salim, Lecio Hannas
    Bomtempo, Virgilio Lopardi
    Moreira, Rubens Martins
    Brisset, Patrick
    Hughes, Catherine E.
    Pant, Harish Jagat
    Thereska, Jovan
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Nuclear Techniques for Monitoring Sediment Dynamics in the Coastal Zone2014In: ENGINEERING GEOLOGY FOR SOCIETY AND TERRITORY, VOL 4: MARINE AND COASTAL PROCESSES, CHAM: SPRINGER INT PUBLISHING AG , 2014, p. 151-155Conference paper (Refereed)
    Abstract [en]

    The knowledge of sediment transport in the coastal region is of vital importance to the management of this critical interface between land and sea, where most of the world population lives. For the assessment of sediment behaviour, hydraulic and sediment measurements, bathymetric survey, mathematical and physical models, are applied. Sediment tracers provide a unique capability for understanding sediment transport assisting in sediment management which cannot be obtained any other way, whether conventional monitoring or physical and numerical models because tracers integrate all the hydrodynamic actions in time and space. Computational fluid dynamics (CFD) is now an essential tool for the management of the natural systems and is increasingly used to study the fate and behaviour of particulates and contaminants. Tracer techniques are often employed to validate hydrodynamic models to enhance confidence in the predictive value of the models. In-situ detection afforded by the use of a radioactive tracer allows accurate quantitative determination of the rate of sediment transport, compared with other tracer methods. Also, it is cost effective and safe: its radiological impact to the environment is minimal. Several case studies, performed in different regions of the world, are presented.

  • 2.
    Bottacin-Busolin, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Combined role of advective pumping and mechanical dispersion on time scales of bed form-induced hyporheic exchange2010In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, p. W08518-Article in journal (Refereed)
    Abstract [en]

    This study analyzes the effect of advective pumping and pore scale dispersion on bed form-induced hyporheic exchange. Advection and dispersion play a competitive role in the exchange dynamics between the porous medium and the overlying stream: Advective fluxes first lead solutes deep into the bed and then back to the stream water, whereas dispersive fluxes favor the transfer of solutes deep into the bed leading to a permanent mass retention. The combined effect of advective exchange and dispersive fluxes produces complexity in the shape of the tails of the residence time distributions (RTDs), which follow at various stages of the process either a power law or an exponential decay. The seepage velocity induced by the stream gradient and, in case of a moving bed, the celerity of the translating bed forms limit the thickness of the advective hyporheic zone, inducing the RTDs to decrease rapidly at late time. This rapid decay can be preceded by a temporal region where the probability density functions (pdf's) tend to be inversely proportional to the square of time, and is followed by a region dominated by dispersion where the pdf's tend to be inversely proportional to the 3/2 power of time. The process shows distinct temporal ranges identified here by appropriate dimensionless parameters. Because of this complex exchange dynamics, models considering pure advection in the porous medium can significantly underestimate solute transfer at long time scales, whereas purely diffusive models of hyporheic exchange appear inadequate to represent the physical processes at an intermediate stage.

  • 3.
    Bottacin-Busolin, Andrea
    et al.
    WET Engn Srl, I-31033 Castelfranco Veneto, TV, Italy.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Musner, Tommaso
    Univ Padua, Dept Chem Proc Engn, I-35131 Padua, Italy.
    Tregnaghi, Matteo
    WET Engn Srl, I-31033 Castelfranco Veneto, TV, Italy.
    Zaramella, Mattia
    WET Engn Srl, I-31033 Castelfranco Veneto, TV, Italy.
    Evidence of distinct contaminant transport patterns in rivers using tracer tests and a multiple domain retention model2011In: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 34, no 6, p. 737-746Article in journal (Refereed)
    Abstract [en]

    Solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges with distinct retention zones. Surface and hyporheic retention processes can be accounted for separately in solute transport models with multiple storage compartments. In the simplest two component model, short term storage can be associated to in-channel transient retention, e.g. produced by riparian vegetation or surface dead zones, and the long-term storage can be associated to hyporheic exchange. The STIR (Solute Transport In Rivers) multiple domain transport model is applied here to tracer test data from three very different Mediterranean streams with distinctive characteristics in terms of flow discharge, vegetation and substrate material. The model is used with an exponential residence time distribution (RTD) to represent surface storage processes and two distinct modeling closures are tested to simulate hyporheic retention: a second exponential RTD and a power-law distribution approximating a known solution for bedform-induced hyporheic exchange. Each stream shows distinct retention patterns characterized by different timescales of the storage time distribution. Both modeling closures lead to very good approximations of the observed breakthrough curves in the two rivers with permeable bed exposed to the flow, where hyporheic flows are expected to occur. In the one case where the occurrence of hyporheic flows is inhibited by bottom vegetation, only the two exponential RTD model is acceptable and the time scales of the two components are of the same magnitude. The significant finding of this work is the recognition of a strong signature of the river properties on tracer data and the evidence of the ability of multiple-component models to describe individual stream responses. This evidence may open a new perspective in river contamination studies, where rivers could possibly be classified based on their ability to trap and release pollutants.

  • 4.
    Bottacin-Busolin, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Zaramella, Mattia
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Modellazione a tempi di residenza del trasporto di soluti nei corsi d'acqua: Applicazione al fiume Yarqon, Israele2008Conference paper (Other academic)
    Abstract [it]

    Il trasporto di soluti nei corsi d’acqua è controllato dall’idrodinamica superficiale e da scambi di massa con distinte zone di ritenzione. La propagazione a valle delle sostanze trasportate è generalmente ritardata dall’immagazzinamento temporaneo in zone morte superficiali, tipicamente zone vegetate o sacche di ritenzione laterali, e nei sedimenti sottostanti, nella cosiddetta zona iporeica. In questo articolo viene presentato un modello concettuale per il trasporto di soluti nei corsi d’acqua (STIR, Solute Transport In Rivers) nel quale i singoli processi di scambio sono rappresentati separatamente da una probabilità di “uptake” e da un’appropriata distribuzione dei tempi di residenza. Ciò rende il modello flessibile e modulare, e consente di incorporare l’effetto di una varietà di processi d’immagazzinamento e reazioni chimiche in modo dettagliato. La capacità del modello di rappresentare situazioni reali è qui dimostrata dall’applicazione al fiume Yarqon, in Israele.

  • 5.
    Bottacin-Busolin, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Singer, Gabriel
    Univ Vienna, Dept Freshwater Ecol.
    Zaramella, Mattia
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Battin, Tom
    Univ Vienna, Dept Freshwater Ecol.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Effects of Streambed Morphology and Biofilm Growth on the Transient Storage of Solutes2009In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 19, p. 7337-7342Article in journal (Refereed)
    Abstract [en]

    Microbial biofilms are the prime site of nutrient and contaminant removal in streams. It is therefore essential to understand how biofilms affect hydrodynamic exchange, solute transport and retention in systems where geomorphology and induced hydrodynamics shape their growth and structure. We experimented with large-scale streamside flumes with streambed landscapes constructed from graded bedforms of constant height and wavelength. Each flume had a different bedform height and was covered with a layer of gravel as substratum for benthic microbial biofilms. Biofilms developed different biomass and physical structures in response to the hydrodynamic conditions induced by the streambed morphology. Step injections of conservative tracers were performed at different biofilm growth stages. The experimental breakthrough curves were analyzed with the STIR model, using a residence time approach to characterize the retention effects associated with biofilms. The retained mass of the solute increased with biofilm biomass and the biofilm-associated retention was furthermore related to bedform height We tentatively relate this behavior to biofilm structural differentiation induced by bed morphology, which highlights the strong linkage between geomorphology, hydrodynamics, and biofilms in natural streams and provide important clues for stream restoration.

  • 6.
    Bottacin-Busolin, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Tait, Simon
    Univ Bradford, Sch Engn Design & Technol.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Chegini, Amir
    Univ Guilan, Dept Civil Engn, Fac Engn.
    Tregnaghi, Matteo
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Probabilistic description of grain resistance from simultaneous flow field and grain motion measurements2008In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 44, no 9, p. W09419-Article in journal (Refereed)
    Abstract [en]

    Experiments were carried out using a mobile gravel bed placed in a tilting flume with a modified particle image velocimetry (PIV) system. Individual grain movements were surveyed using data from time series of images. Near-bed velocity flow field measurements were made simultaneously above the same area of the sediment surface by applying cross-correlation techniques to the collected plan view images. Statistics of grain motions were collected through a semiautomatic procedure. Significant changes in the flow field were observed in the proximity of the entrained or deposited particles. A strong correlation is shown between the changes in the local streamwise and lateral velocity and the movement of the grains. The theory of Grass is revisited and developed based on the experimental results. The probability distribution of individual grain resistance has been derived from the statistics of the near-bed velocity field and of the entrainment risk.

  • 7.
    Bottacin-Busolin, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Tregnaghi, Matteo
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Tait, Simon
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Misurazioni del campo di moto in prossimità di grani in movimento2006Conference paper (Refereed)
    Abstract [it]

    È stata condotta una serie di esperimenti utilizzando una canaletta di laboratorio a fondo inclinabile ed un avanzato sistema PIV (Particle Image Velocimetry). L’apparato sperimentale ha permesso un’indagine a scala di grano delle condizioni di movimento incipiente. Sul fondo della canaletta si è disposto un letto di materiale granulometrico uniforme, che nelle prove è stato sottoposto all’azione continua di una portata d’acqua costante. Il regime idrodinamico approssima il moto uniforme della corrente e la condizione di incipiente movimento dei grani. Ciascun test è stato condotto per una durata di 10 – 18 ore, durante la quale sono state registrate misurazioni per periodi di circa cinque minuti ad intervalli regolari. Il campo di moto istantaneo è stato misurato all’interno di un’area di circa 400 cm2, posta su un piano inizialmente parallelo al letto, ad una distanza da esso di circa 5 mm. Un apposito software ha consentito la costruzione delle matrici del campo di velocità istantaneo, tramite la tecnica di cross-correlazione delle immagini applicata a particelle traccianti. Mediante una fotocamera digitale si sono ottenute, inoltre, delle sequenze di foto della superficie dei sedimenti, ognuna delle quali è contemporanea ad una misura del campo di moto. Tramite una procedura semi-automatica di elaborazione dei dati è stata prodotta una statistica riguardante il moto dei sedimenti. Analizzando le sequenze è stato possibile riconoscere lo spostamento dei grani superficiali; in seguito, osservando l’andamento temporale delle velocità in prossimità delle particelle in movimento, sono stati individuati dei cambiamenti del campo di moto locale che si verificano contemporaneamente alla loro rimozione o deposizione. Tali variazioni di velocità, che possono interessare la componente longitudinale e laterale o le rispettive fluttuazioni dalla media, appaiono una diretta conseguenza del moto delle particelle. È inoltre rilevante la correlazione tra “salti” positivi di velocità in corrispondenza di un grano che viene mosso e “salti” negativi nel caso di un grano che si deposita.

  • 8.
    Dargahi, Bijan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Flow characteristics of bottom outlets with moving gates2010In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 48, no 4, p. 476-482Article in journal (Refereed)
    Abstract [en]

    This study investigates the discharge characteristics of a bottom outlet with a moving gate by Flow3D. Experimental results for a scale model outlet of the Aswan Dam, Egypt, were used. Two different flow features were found. Pressurized flow established if the flume was filled and then the gate was slowly opened. However, a free surface flow occurred if the gate was fully opened and the entire flume was slowly flooded with water. The numerical simulations successfully captured the two flow patterns as well as the discharges and water surface profiles. The discharges were predicted with sufficient accuracy using the first-order momentum advection scheme. In comparison with the k-epsilon turbulence model, the Re-Normalization Group model yields the best agreement with the experiments. The model performed with similar accuracy for both model and prototype cases.

  • 9.
    Fabian, Mark
    et al.
    SUNY Coll Environm Sci & Forestry, Dept Environm Resources Engn, Baker Labs 423, Syracuse, NY 13210 USA.
    Endreny, Theodore
    SUNY Coll Environm Sci & Forestry, Dept Environm Resources Engn, Baker Labs 423, Syracuse, NY 13210 USA.
    Bottacin-Busolin, Andrea
    Water & Environm Technol Engn Srl, I-31033 Treviso, Italy.
    Lautz, Laura
    Syracuse Univ, Dept Earth Sci, Heroy Geol Lab 204, Syracuse, NY 13244 USA.
    Seasonal variation in cascade-driven hyporheic exchange, northern Honduras2011In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 25, no 10, p. 1630-1646Article in journal (Refereed)
    Abstract [en]

    A characterization of hyporheic exchange for dry and wet season baseflow, as well as partially dewatered discharge, was done in Prieta Creek, a first-order cascade in northern Honduras. The cascade had discharges from 1 to 15 1 s(-1), had average slopes of 12%, pool spacing of 3 m, and shallow substrate of sand and gravel. Tracer tests were conducted in a 15-m sub-reach, a length considered to be adequate for the experiment based on the DaI test, a ratio of exchange and transport processes. In the three tests, between 9 and 18% of tracer was not recovered, possibly due to entrainment in flowpaths passing beneath the downstream monitoring location. Tracer data were analysed by the one-dimensional transport with inflow and storage (OTIS) transient storage model (TSM) to derive standard exchange parameters, and by the solute transport in rivers (STIR) model to examine hyporheic residence time distributions (RTDs). The best fit of the observed tracer breakthrough curves was obtained by using the STIR model with a combination of two exponential RTDs to represent hyporheic retention. With increasing discharge, the OTIS model predicted increasing storage exchange fluxes and exchange coefficients and decreasing storage zone areas and transient storage times, which are trends supported by riparian and streambed piezometric head data. Riparian water levels rose during the transition from the dry to wet season, which could constrict the hyporheic storage zone. Thirteen of the 19 streambed piezometers recorded seasonal changes in hydraulic gradients and flux direction, with fewer yet stronger upwelling zones during higher discharges. The MODFLOW model missed the observed seasonal changes, possibly due to subtle changes in the seasonal change in water surface profiles. We conclude that partially dewatered dry season exchange, compared to wet season exchange, was initiated and terminated with smaller pressure gradients and, in different streambed locations, was smaller in volume, had longer residence times, and may connect with deeper and longer flow paths.

  • 10.
    Gröndahl, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Chemical Analysis of Water and Sediments - Coastman - Estonia, Fauna and Flora2005In: Report to the Department of Environmental Engineering, Tallinn, Technical University, Estonia: European Comission in Estonia , 2005Chapter in book (Refereed)
  • 11. Gulbinskas, Saulius
    et al.
    Mileriene, Rosita
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Blažauskas, Nerijus
    Beach nourishment for shore protection in the Lithuanian Baltic sea coast2011In: Artificial beaches, artificial islands and other structures in the coastal and offshore areas: Proceedings of the 2nd International Conference 'Construction of the Artificial Lands in the Coastal and Offshore Areas' / [ed] Khabidov, A.Sh., Publishing House of the Siberian Branch of Russian Academy of Sciences , 2011Conference paper (Refereed)
  • 12.
    Gustafsson, David
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Physics.
    Ahlberg, Jesper
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Physics.
    Granlund, Nils
    Luleå University of Technology.
    Lindström, Göran
    Sveriges meteorologiska och hydrologiska institut.
    Wetterhall, Fredrik
    Sveriges meteorologiska och hydrologiska institut.
    Lundberg, Angela
    Luleå University of Technology.
    Distribuerade system för förbättrade snö- och avrinningsprognoser. Integration i hydrologiska modeller: Delrapport 12009Report (Other academic)
  • 13.
    Ivansen, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Hydrauliska effekter av avbördade extremflöden: Fallstudie på en damm i Norrland2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Flödesdimensionering är något som används världen över när det kommer till konstruktionen och hanteringen av byggnader i vattendrag. I Sverige har flödeskommitén, bestående av SMHI och intressenter från vattenkraftsindustrin, tagit fram flödesdimensioneringsriktlinjerna som blivit praxis för svenska dammägare. Utifrån dessa riktlinjer får dammar olika flödesdimensioneringsklassningar beroende på vad konsekvenserna blir av olika högflöden. Detta arbete bygger på en nyligt genomförd konsekvensutredning på en av Jämtkrafts dammar i mellersta Norrland. Dammen, som går under namnet Damm B i denna rapport, har tidigare haft flödesdimensioneringsklass II men bedöms nu tillhöra flödesdimensionerings klass I. Dammen ska utifrån detta kunna avbörda ett klass I-flöde på 1690 m3/s till skillnad från det tidigare kravet på 1035 m3/s (klass II-flöde). Syftet med denna rapport äratt undersöka vilka effekter den naturliga tillrinningen av dessa och mellanliggande flöden har på olika objekt och områden nedströms Damm B. Med modelleringsverktyget MIKE 11 konstrueras en en-dimensionell flödesmodell för flödessimuleringar och avläsning av vattennivåer. Simuleringarna visar att den största delen av nedströms undersökta objekt påverkas mellan flödena 1100 m3/s och det så kallade 1000-års flödet på 1376 m3/s där risken för människoliv börjar vid det senare. Redan under klass II-flödet sker viss översvämning på de strandnära vägarna i området. Mellan 1100 m3/s samt 1200 m3/s börjar den mindre dammen nedströms (Damm C) riskera att gå till brott för att sedan överströmmas vid 1400 m3/s. Uträkning av skjuvspänningen berättar att det finns erosionsrisker för korndiametrar på upp till ca 2 cm i vissa erosionsbenägna områden. Denna erosionsbenägenhet inträffar för flöden under 1300 m3/s innan dammbrott har skett i Damm C. Vattenytans lutning minskartill följd av en större motdämning vilket därefter orsakar att minskningen av skärspänningen sker snabbare än den ökning som uppkommer till följd av ett stigande vattendjup. Vattenytan stiger dock och berör områden som inte brukar ligga under vatten. Detta kan leda till kornfraktioner som inte har transporteras bort vid tidigare flöden nu riskerar göra detta vilket bland annat kan bilda drivgods. Flödesdimensioneringsriktlinjerna som har tagits fram i Sverige bygger på miljöbalkens allmänna hänsynsregler vilket gör dem till en bra mall för dammägare att följa. När funderingar dock finns att inte bygga ut avbördningskapaciteten helt behöver det funderas på hur mycket ett eventuellt dammbrott skulle påverka den egna anläggningen och förtroendet från myndigheter samt allmänheten. I fallet med Damm B kommer de flesta objekten som undersöks att beröras vid en naturlig tillrinning på 1400 m3/s. Det är därför av intresse att genomföra noggrannare dammbrotts simuleringar för att hitta ett flöde mellan 1400 m3/soch 1690 m3/s där inga större ytterligare konsekvenser från ett dammbrott uppstår. Till följd av de svårheter och osäkerheter som valetav en lägrea vbördningskapacitet medför motiverar denna rapport dock till en utökad kapacitet för ett klass I-flöde i Damm B och undersöka möjligheterna för ökad avbördning vid Damm C. Detta kan även kompletteras med en omfattande samordnad beredskapsplan längs med älven och ett utökat översvämnings-/erosionsskydd på utsatta områden. 

  • 14. Lin, C.
    et al.
    Kao, M. -J
    Wong, W. -Y
    Tsai, C. -P
    Chang, K. -T
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Characteristics of flow separation and hydraulic jump during run-down motion of shoaling solitary wave traveling over steep sloping bottom2016In: Proceedings of the International Offshore and Polar Engineering Conference, International Society of Offshore and Polar Engineers , 2016, p. 724-731Conference paper (Refereed)
    Abstract [en]

    The features of velocity fields for the evolution of shoaling solitary wave, having a wave-height to water-depth ratio of 0.363 and propagating over a 1:3 sloping bottom, are investigated experimentally. A flow visualization technique using particle trajectory method and a high-speed particle image velocimetry (HSPIV) system employing a high-speed digital camera were used. This study mainly focuses on the occurrence of separated shear layer from the sloping bottom, evolved vortex structure, subsequent hydraulic jump, and curling jet of the backward breaking wave impinging upon the free surface of retreated flow during the run-down motion of the shoaling solitary wave.

  • 15.
    Marion, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Bottacin-Busolin, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Tait, Simon
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Tregnaghi, Matteo
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Near-bed flow field measurements at threshold of sediment motion2007In: PROCEEDINGS OF THE CONGRESS - INTERNATIONAL ASSOCIATION FOR HYDRAULIC RESEARCH, 2007, p. 401-Conference paper (Refereed)
    Abstract [it]

    Several experimental tests were carried out using a gravel bed tilting flume and an ad­vanced Particle Image Velocimetry (PIV) system. Sediment movement at the threshold was surveyed at the grain scale under uniform flow conditions. A natural river gravel with well sorted sediment was used. Flow field measurements were made over an area of approximately 400 cm2, on a plane located at 5 mm above the original sediment bed. Image processing and cross-correlation techniques were used to obtain flow velocities. Sequences of images of the bed surface were taken simultaneously with the measurements of the flow field. Statistics of the movements of the grains were collected through a semi-automatic procedure. Significant changes in the local flow field were observed in the proximity of the entrained or deposited particles. Such variations of velocity, which can be either in terms of the longitudinal and la­teral components or in terms of the relevant fluctuations from the time average, appear as a direct effect of the removal or deposition of individual grains. A strong correlation is shown between the changes in the streamwise velocity and the movement of the particles: local ve­locity increases were observed to correspond with the entrainment of grains, while local ve­locity reductions occurred as a grain was deposited.

  • 16.
    Marion, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotechn Engn.
    Packman, Aaron
    Northwestern Univ, Dept Civil & Environm Engn, Evanston.
    Zaramella, Mattia
    Univ Padua, Dept Hydraul Maritime Environm & Geotechn Engn.
    Bottacin-Busolin, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotechn Engn.
    Hyporheic flows in stratified beds2008In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 44, no 9, p. W09433-Article in journal (Refereed)
    Abstract [en]

    Surface-subsurface exchange fluxes are receiving increasing interest because of their importance in the fate of contaminants, nutrients, and other ecologically relevant substances in a variety of aquatic systems. Solutions have previously been developed for pore water flows induced by geometrical irregularities such as bed forms for the cases of homogeneous sediment beds and idealized heterogeneous beds, but these solutions have not accounted for the fact that streambed sediments are subject to sorting processes that often produce well-defined subsurface structures. Sediments at the streambed surface are often coarser than the underlying material because of size-selective sediment transport, producing relatively thin armor layers. Episodic erosional and depositional processes also create thick layers of different composition within the porous medium, forming stratified beds. A series of experiments were conducted to observe conservative solute transport in armored and stratified beds. An analytical solution was developed for advective exchange with stratified beds and provides appropriate scaling of the physical variables that control exchange flows. The results show that armor layers are too thin to significantly alter the advective pumping process but provide significant solute storage at short time scales. Stratified beds with layers of significant thickness favor development of horizontal flow paths within the bed and change the rate of solute transfer across the stream-subsurface interface compared to homogeneous beds.

  • 17.
    Marion, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Zaramella, Mattia
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Bottacin-Busolin, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Solute transport in rivers with multiple storage zones: The STIR model2008In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 44, no 10, p. W10406-Article in journal (Refereed)
    Abstract [en]

    Solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges between the surface stream and distinct retention zones. This paper presents a residence time model for stream transport of solutes, Solute Transport in Rivers (STIR), that accounts for the effect of the stream-subsurface interactions on river mixing. A stochastic approach is used to derive a relation between the in-stream solute concentration and the residence time distributions (RTDs) in different retention domains. Particular forms of the RTD are suggested for the temporary storage within surface dead zones and for bed form-induced hyporheic exchange. This approach is advantageous for at least two reasons. The first advantage is that exchange parameters can generally be expressed as functions of physical quantities that can be reasonably estimated or directly measured. This gives the model predictive capabilities, and the results can be generalized to conditions different from those directly observed in field experiments. The second reason is that individual exchange processes are represented separately by appropriate residence time distributions, making the model flexible and modular, capable of incorporating the effects of a variety of exchange processes and chemical reactions in a detailed way. The capability of the model is illustrated with an example and with an application to a field case. Analogies and differences with other established models are also discussed.

  • 18. Mazzoleni, M.
    et al.
    Dottori, F.
    Brandimarte, Luigia
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Tekle, S.
    Martina, M. L. V.
    Effects of levee cover strength on flood mapping in the case of levee breach due to overtopping2017In: Hydrological Sciences Journal, ISSN 0262-6667, E-ISSN 2150-3435, Vol. 62, no 6, p. 892-910Article in journal (Refereed)
    Abstract [en]

    The reliability of a levee system is a crucial factor in flood risk management. In this study we present a probabilistic methodology to assess the effects of levee cover strength on levee failure probability, triggering time, flood propagation and consequent impacts on population and assets. A method for determining fragility curves is used in combination with the results of a one-dimensional hydrodynamic model to estimate the conditional probability of levee failure in each river section. Then, a levee breach model is applied to calculate the possible flood hydrographs, and for each breach scenario a two-dimensional hydrodynamic model is used to estimate flood hazard (flood extent and timing, maximum water depths) and flood impacts (economic damage and affected population) in the areas at risk along the river reach. We show an application for levee overtopping and different flood scenarios for a 98 km reach of the lower Po River in Italy. The results show how different design solutions for the levee cover can influence the probability of levee failure and the consequent flood scenarios. In particular, good grass cover strength can significantly delay levee failure and reduce maximum flood depths in the flood-prone areas, thus helping the implementation of flood risk management actions.

  • 19.
    Reinius, E.
    KTH. VBB, SWECO, Sweden.
    Method To Reduce The Groundwater Flow Around A Subsurface Storge Of Nuclear Waste1981In: Subsurface Space: Environmental Protection Low Cost Storage Energy Savings, Elsevier, 1981, Vol. 2, p. 977-982Chapter in book (Other academic)
    Abstract [en]

    Ground water flow through an underground repository for nuclear waste located 500 m below the ground surface as proposed by Swedish authorities may be considerably reduced by surrounding the repository with a zone of constant potential like Faraday's cage in electricity. The zone consists of tunnels and boreholes between them.

  • 20. Schmadel, Noah M.
    et al.
    Neilson, Bethany T.
    Heavilin, Justin E.
    Stevens, David K.
    Worman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    The influence of spatially variable stream hydraulics on reach scale transient storage modeling2014In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, no 12, p. 9287-9299Article in journal (Refereed)
    Abstract [en]

    Within the context of reach scale transient storage modeling, there is limited understanding of how best to establish reach segment lengths that represent the effects of spatially variable hydraulic and geomorphic channel properties. In this paper, we progress this understanding through the use of channel property distributions derived from high-resolution imagery that are fundamental for hydraulic routing. We vary the resolution of reach segments used in the model representation and investigate the minimum number necessary to capture spatially variable influences on downstream predictions of solute residence time probability density functions while sufficiently representing the observed channel property distributions. We also test if the corresponding statistical moments of the predictions provide comparable results and, therefore, a method for establishing appropriate reach segment lengths. We find that the predictions and the moment estimates begin to represent the majority of the variability at reach segment lengths coinciding with distances where observed channel properties are spatially correlated. With this approach, reach scales where the channel properties no longer significantly change predictions can be established, which provides a foundation for more focused transient storage modeling efforts.

  • 21.
    Setegn, Shimelis Gebriye
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Melesse, A. M.
    Abbaspour, K.
    Dargahi, Bijan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Srinivasan, R.
    Effect of Downscaling Methods on the Assessment of the Impact of Climate Change in Watershed Scale Management Models2009In: Proceedings of the American Water Resources Association - AWRA 2009: Spring Specialty Conference: Managing Water Resources Development in a Changing Climate/TPS-09-1, 2009Conference paper (Refereed)
  • 22.
    Setegn, Shimelis Gebriye
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Melesse, A. M.
    Dargahi, Bijan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Srinivasan, R.
    Water Resources Variability as a Result of Changing Climate: A Case Study in the Lake Tana Basin, Blue Nile Ethiopia2009In: Proceedings of the American Water Resources Association (AWRA) 2009: Spring Specialty Conference: Managing Water Resources Development in a Changing Climate /TPS-09-1, 2009Conference paper (Refereed)
  • 23. Taddele, Y. D.
    et al.
    Setegn, Shimelis Gebriye
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Berndtsson, R.
    Hydrological Response of Gilgel Abay River Flow to Climate Change, Lake Tana Basin, Ethiopia2009In: Proceedings of the 5th International SWAT Conference, 2009Conference paper (Refereed)
  • 24.
    Thunqvist, Eva-Lotta
    KTH, School of Technology and Health (STH), Centres, Centre for Health and Building, CHB.
    Enskilda brunnar och saltvatteninträngning på Ornö2011Report (Other academic)
    Abstract [sv]

    Haninge kommun är en kustkommun i en storstadsregion. Befolkningen i Stockholms län ökar kontinuerligt och så även inflyttningen till i Haninge kommun. Fritidsboende övergår i permanentboende och särskilt attraktivt är det att bo vid kusten. Även på öar i skärgården med fast båtförbindelse ökar befolkningen. I skärgården sker vattenförsörjningen oftast med enskilda brunnar. Ett kustnära läge för en brunn innebär en ökad risk för saltvatteninträngning vid stora uttag.

    Syftet med denna studie är att kartlägga förekomsten av enskilda brunnar på Ornö samt att utreda om kustnära brunnar har förhöjda kloridhalter till följd av saltvatteninträngning. Ornö, är en ö belägen i Stockholms skärgård i Haninge kommun, med en yta av nästan 5000 ha och med 279 permanentboende. På sommaren ökar dock siffran markant då det finns ett stort antal fritidsboende på ön.

    År 2009 skickades 762 enkäter ut till Ornös fastighetsägare. Totalt erhölls 606 svar, dvs en 80% svarsfrekvens. 349 fastighetsägare uppgav att de tog sitt vatten från en enskild brunn, 212 fastigheter var anslutna till en gemensam brunn. Uppgifter om brunnars djup visade sig vara svåra att erhålla. I den databas som upprättades av Haninge kommun framgår endast vilka fastigheter som har en brunn, inte var på fastigheten brunnen ligger.

    I augusti 2010 provtogs 42 brunnar. Sju av brunnarna hade en kloridhaltkoncentration av 100mg/l eller mer. Nio brunnar hade en natriumkoncentration av 100mg/l eller mer.

    Saltvattenpåverkan av brunnsvatten förekommer främst när grundvattenuttagen överstiger grundvattenbildningen inom ett område. Detta kan ske vid ökande grundvattenuttag och/eller perioder med dålig grundvattenbildning. Salthalten i brunnsvatten varierar därför med tiden. Studien visade att det fanns brunnar med höga klorid

    och natriumhalter i områdena Ornöboda, Hässelmara, Långviksholmen och Brevik. De högsta halterna fanns på Långviksholmen som också har ett mycket begränsat tillrinningsområdet. Två av brunnarna tillhörde samfälligheter och har troligen stora uttag vilket kan öka risken för saltvatteninträngning.

    Även fortsättningsvis bör information om brunnars läge och kemiska data (i det fall fastighetsägaren genomför en analys av brunnsvattnet) samlas i en brunnsdatabas hos Haninge kommun. Genom brunnsdatabasen får kommunen ett relevant beslutsunderlag för planering och uppföljning. Det fortsatta arbetet bör omfatta utformning av rutiner för att sammanställa och i framtiden införa data om enskilda brunnar i en GIS

    databas. Denna databas kan tillsammans med data från SGUs brunnsarkiv ge ett underlag för kartor som visar områden för ökad risk för saltvatteninträngning. Vidare bör det ske en uppföljning och återkommande analys av brunnar i områden där kloridhalterna är höga. Det är också viktigt att informera fastighetsägare om risken för saltvatteninträngning beskrivs samt utfärda rekommendationer om vattenanvändning tex med hänvisning till SGUs rapporter om grundvattennivåer.

  • 25.
    Tregnaghi, Matteo
    et al.
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Bottacin-Busolin, Andrea
    Water & Environm Technol WET Engn Srl, I-31033 Treviso, Italy.
    Tait, Simon
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy .
    3D near‐bed flow field measurements at low sediment transport rates2010In: / [ed] Dittrich, Koll, Aberle & Geisenhainer, Bundesanstalt für Wasserbau , 2010, p. 785-792Conference paper (Refereed)
    Abstract [en]

    Experimental tests were carried out using a gravel bed in a tilting flume and a three camera 3D Particle Image Velocimetry (PIV) system. Sediment movement at variable transport rates was surveyed at the grain scale under uniform flow conditions. A natural river gravel with a well sorted sediment was used. This was subject to steady, uniform flows that generated a range of shear stresses that mobilized the sediment. 3D flow field measurements were made over a plane located few millimeters above the original sediment bed. Image processing and cross-correlation techniques were used to obtain high resolution spatial and high-frequency temporal information of flow velocities. Sequences of images of the bed surface were taken simultaneously with the flow field measurements using an additional camera. An experimental approach is illustrated which links grain behavior with local velocity patterns. Such patterns of velocity can be either in terms of the three velocity components or in terms of the relevant time averaged Reynolds stresses. The potential is shown to develop statistically significant relationships which could describe the stochastic nature of sediment transport at different flow conditions.

  • 26.
    Tregnaghi, Matteo
    et al.
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Bottacin-Busolin, Andrea
    Water & Environm Technol WET Engn Srl, I-31033 Treviso, Italy.
    Tait, Simon
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Linking the near-bed velocity field with grain motion over a gravel deposit2010Conference paper (Refereed)
    Abstract [en]

    Experimental tests were carried out in a tilting laboratory flume using a modified 3D Particle Image Velocimetry (PIV) system. A gravel bed deposit was placed in the flume and subjected to steady, uniform flows that caused a range of sediment transport mobilities. Flow velocity measurements were made, at a frequency of 45Hz and at a grain scale spatial resolution, over an area of 220x40 mm2, on a plane located just above the original sediment bed. Image processing and cross-correlation techniques were used to obtain the flow velocity time series in this measurement plane. An additional camera provided sequences of images of the bed surface, at the same location, which were taken simultaneously with the measurements of the flow field. By comparing grain motion in the bed camera images with the velocity data, changes in the local flow field can be linked with the entrainment or deposition of individual particles, either in terms of any of the three velocity components or in terms of the relevant Reynolds stresses. The experimental data set contained the movement of hundreds of grains from tests exhibiting a range of average sediment mobilities. Using this knowledge work is continuing to develop statistically based models of grain entrainment for natural sediment at a range of flow conditions.

  • 27.
    Tregnaghi, Matteo
    et al.
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Bottacin-Busolin, Andrea
    Water & Environm Technol WET Engn Srl, I-31033 Treviso, Italy.
    Tait, Simon
    Univ Bradford, Sch Engn Design & Technol, Bradford BD7 1DP, W Yorkshire, England.
    Modelling time varying scouring at bed sills2011In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 36, no 13, p. 1761-1769Article in journal (Refereed)
    Abstract [en]

    In this paper a modelling approach is presented to predict local scour under time varying flow conditions. The approach is validated using experimental data of unsteady scour at bed sills. The model is based on a number of hypotheses concerning the characteristics of the flow hydrograph, the temporal evolution of the scour and the geometry of the scour hole. A key assumption is that, at any time, the scour depth evolves at the same rate as in an equivalent steady flow. The assumption is supported by existing evidence of geometrical affinity and similarity of scour holes formed under different steady hydraulic conditions. Experimental data are presented that show the scour hole development downstream of bed sills due to flood hydrographs follow a predictable pattern. Numerical simulations are performed with the same input parameters used in the experimental tests but with no post-simulation calibration. Comparison between the experimental and model results indicates good correspondence, especially in the rising limb of the flow hydrograph. This suggests that the underlying assumptions used in the modelling approach are appropriate. In principle, the approach is general and can be applied to a wide range of environments (e.g. bed sills, step-pool systems) in which scouring at rapid bed elevation changes caused by time varying flows occurs, provided appropriate scaling information is available, and the scour response to steady flow conditions can be estimated.

  • 28. Wang, Jun-Zhi
    et al.
    Worman, Anders
    Bresciani, Etienne
    Wan, Li
    Wang, Xu-Sheng
    Jiang, Xiao-Wei
    On the use of late-time peaks of residence time distributions for the characterization of hierarchically nested groundwater flow systems2016In: JOURNAL OF HYDROLOGY, ISSN 0022-1694, Vol. 543, p. 47-58Article in journal (Refereed)
    Abstract [en]

    Previous studies on the characterization of hierarchically nested groundwater flow systems have mainly been based on the spatial distribution analyses of groundwater pathways. In this paper, by considering the discrete nature of the temporal behavior induced by different hierarchical flow systems, a new approach is proposed. The core of this approach is to use the critical residence times defined by the late-time peaks of residence time distributions (RTDs) to divide the groundwater flow field into local, intermediate and regional systems as described by Toth (1963). We first introduce Tothian basins of a 2D cross section and a 3D domain as synthetic test cases. The feasibility of the approach is demonstrated by comparing the partitioning results given by the dividing streamlines associated with internal stagnation points in the 2D Tothian basin and by the hydraulic connections between recharge and discharge zones in the 3D Tothian basin. Then, the Dosit River Watershed in Northwestern China is introduced as a field case study. Using the calibrated 3D groundwater flow model, one distinct late-time peak is identified from the RTD and indicates that the Dosit River Watershed can generally be regarded as a two-order nested flow structure with local and regional flow systems. This approach can be used to identify the volumes occupied by different orders of flow systems in 3D, and therefore opens up a new perspective in the study of the 3D nature of basin-scale groundwater flow.

  • 29.
    Wörman, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Bottacin-Busolin, A.
    Zmijewski, Nicholas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Riml, Joakim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Spectral decomposition of regulatory thresholds for climate-driven fluctuations in hydro- and wind power availability2017In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, no 8, p. 7296-7315Article in journal (Refereed)
    Abstract [en]

    Climate-driven fluctuations in the runoff and potential energy of surface water are generally large in comparison to the capacity of hydropower regulation, particularly when hydropower is used to balance the electricity production from covarying renewable energy sources such as wind power. To define the bounds of reservoir storage capacity, we introduce a dedicated reservoir volume that aggregates the storage capacity of several reservoirs to handle runoff from specific watersheds. We show how the storage bounds can be related to a spectrum of the climate-driven modes of variability in water availability and to the covariation between water and wind availability. A regional case study of the entire hydropower system in Sweden indicates that the longest regulation period possible to consider spans from a few days of individual subwatersheds up to several years, with an average limit of a couple of months. Watershed damping of the runoff substantially increases the longest considered regulation period and capacity. The high covariance found between the potential energy of the surface water and wind energy significantly reduces the longest considered regulation period when hydropower is used to balance the fluctuating wind power. Plain Language Summary The availability of renewable energy fluctuates significantly with climate and needs to be regulated to be sufficient at all times. This regulation can be achieved by storing hydropower in water reservoirs, but is complicated by the vast spatial distribution of storage locations, size variations in reservoirs, the covariation of renewable energy, and the range of frequencies that need to be considered in climate variations. This study provides a new method of analysis that can provide estimates of the most effective use of hydropower reservoirs and the limits of their use for regulating renewable energy. Based on data from entire Sweden we show how the storage bounds can be related to a spectrum of the climate-driven modes of variability in water availability and to the covariation between water and wind availability. The high covariance found between the potential energy of the surface water and wind energy significantly reduces the longest considered regulation period when hydropower is used to balance the fluctuating wind power.

  • 30.
    Wörman, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Lindstrom, G.
    Riml, Joakim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    The power of runoff2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 548, p. 784-793Article in journal (Refereed)
    Abstract [en]

    Although the potential energy of surface water is a small part of Earth's energy budget, this highly variable physical property is a key component in the terrestrial hydrologic cycle empowering geomorphological and hydrological processes throughout the hydrosphere. By downscaling of the daily hydrometeorological data acquired in Sweden over the last half-century this study quantifies the spatial and temporal distribution of the dominating energy components in terrestrial hydrology, including the frictional resistance in surface water and groundwater as well as hydropower. The energy consumed in groundwater circulation was found to be 34.6 TWh/fy or a heat production of approximately 13% of the geothermal heat flux. Significant climate driven, periodic fluctuations in the power of runoff, stream flows and groundwater circulation were revealed that have not previously been documented. We found that the runoff power ranged from 173 to 260 TWh/y even when averaged over the entire surface of Sweden in a five-year moving window. We separated short-term fluctuations in runoff due to precipitation filtered through the watershed from longer-term seasonal and climate driven modes. Strong climate driven correlations between the power of runoff and climate indices, wind and solar intensity were found over periods of 3.6 and 8 years. The high covariance that we found between the potential energy of surface water and wind energy implies significant challenges for the combination of these renewable energy sources.

  • 31.
    Zaramella, Mattia
    et al.
    WET Engn Srl, I-31033 Castelfranco Veneto, TV, Italy.
    Bottacin-Busolin, Andrea
    WET Engn Srl, I-31033 Castelfranco Veneto, TV, Italy.
    Musner, Tommaso
    Univ Padua, Dept Chem Proc Engn, I-35131 Padua, Italy.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Determining surface and hyporheic retention in the Yarqon River, Israel2010In: / [ed] Dittrich, Koll, Aberle & Geisenhainer, Braunschweig, Germany: Bundesanstalt für Wasserbau , 2010, p. 1767-1774Conference paper (Refereed)
    Abstract [en]

    Solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges with distinct retention zones. The downstream propagation of transported substances such as nutrients and contaminants is affected by the transient storage in surface dead zones (e.g., eddies, vegetated pockets) and in the permeable subsurface in the so called hyporheic zones. General residence time models allow to represent surface and hyporheic retention processes via specific modelling closures, yet current stream tracer tests do not allow a clear separation of the different storage components. A conceptual distinction can be given by associating in-channel transient storage to relatively short time scales and hyporheic retention to longer time scales. Based on this conceptual separation, we apply the STIR (Solute Transport In Rivers) model to interpret tracer test data from four different reaches of the Yarqon river, in Israel. In the model we use an exponential residence time distribution (RTD) to represent surface storage processes and we experiment with two distinct modelling closures to simulate hyporheic retention: an exponential RTD and a distribution approximating Elliott and Brooks’ (1997) solution for bedform-induced hyporheic exchange which is asymptotically a power law. Both modelling closures lead to acceptable approximations of the observed breakthrough curves, but better fits are obtained using an exponential distribution to represent hyporheic (long timescale) retention. We then compare the results in terms of retained mass. The comparison shows that, although the two modelling choices lead to differences in the calculated retained mass, the model response in terms of relative importance of surface and hyporheic retention in the four reaches examined remains unaltered.

  • 32.
    Zaramella, Mattia
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Packman, Aaron
    Northwestern Univ, Dept Civil & Environm Engn, Evanston, IL 60208 USA.
    Bottacin-Busolin, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn, I-35131 Padua, Italy.
    Effect of the vertical structure of a porous bed on hyporheic exchange2007In: PROCEEDINGS OF THE CONGRESS: INTERNATIONAL ASSOCIATION FOR HYDRAULIC RESEARCH, 2007, p. 274-Conference paper (Refereed)
    Abstract [it]

    Hyporheic exchange provides an important control on contaminant fluxes across the stream-subsurface interface. Several experimental studies have identified the dominant processes affecting hyporheic exchange. The surface layer, a few particle diameter thick, is affected by turbulent diffusion from the main flow, while deeper exchange is due to advective flow generated by pressure head variations at the stream/bed interface. This pressure head gradients are the result of the geometrical irregularities of the interface such as bends and bedforms. The structure of sediment beds is in turn a result of sediment transport processes acting at various time scales. Many structures of river beds develop as a vertical granulometric variation. Typical sorting processes like armoring and selective erosion and deposition produce layers having a thickness ranging from a few particle diameters to several meters. A layered bed structure has been constructed in a laboratory flume, both by laying sediments in layers and by allowing armoring to develop from a graded sediment mixture. The bed structure was measured using surface sampling procedures with appropriate area-to-volume conversion methods. Mass exchange between the stream and the bed was measured using tracers in a fully recirculated hydraulic system. Several combinations of armored and layered beds, either with flat beds or bedforms have been used.

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