Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    Replication Data for: Effect of non-migrating bars on dune dynamics in a lowland river
    Ruijsscher, Timo de; Naqshband, Suleyman ; Hoitink, Ton - \ 2020
    Wageningen University & Research
    bars - bed level - discharge - dunes - longitudinal training dams - multibeam echosounding - roughness - Waal River - water level
    As dunes and larger scale bed forms such as bars coexist in rivers, the question arises whether dune dynamics are influenced by interaction with the underlying bed topography. The present study aims to establish the degree in which dune characteristics in two and three dimensions are influenced by an underlying topography dominated by non-migrating bars. As a case study, a 20 km stretch in the Waal River in the Netherlands is selected, which represents a sand-bed lowland river. At this location, longitudinal training dams (LTDs) have recently been constructed to ensure sufficient navigation depth during periods with low water levels, and to reduce flood risk. By using data covering two-year-long periods before and after LTD construction, the robustness of the results is investigated. Before LTD construction, dune characteristics show large variability both spatially and temporally, with dunes being longer, lower, less steep and having a lower lee side angle when they are located on bar tops. The correlation between dune characteristics and the underlying bed topography is disrupted by unsteady conditions for which the dunes are in a state of transition. The bar pattern causes tilting of dune crest lines, which may result from a transverse gradient in bed load sediment transport. As a result of LTD construction, the hydraulic and morphological conditions have changed significantly. Despite this, the main conclusions still hold, which strengthens the validity of the results.
    Effect of microparticulated whey protein on sensory properties of liquid and semi-solid model foods
    Liu, K. ; Stieger, M.A. ; Linden, E. van der; Velde, Fred van de - \ 2016
    Food Hydrocolloids 60 (2016). - ISSN 0268-005X - p. 186 - 198.
    MWP - lubrication - Particle size - creaminess - roughness - sensory
    This work describes the sensory properties of microparticulated whey protein (MWP) particles in relation to their rheological and tribological properties. The aim of this work is to obtain a better understanding of the sensory perception of MWP particles compared to oil droplets in liquid and semi-solid matrices. We used liquid MWP-o/w emulsions with controlled viscosities and semi-solid MWP-emulsion-filled gelatin gels as food model systems. Consistent with our previous findings, MWP showed good lubrication properties probably due to ball bearing mechanism in both liquid and semi-solid systems. Sensory results (QDA) revealed that small MWP particles contributed to perception of creaminess due to their lubrication property. Large MWP contributed to the rough and powdery perception, and thus suppressed perception of creaminess. MWP did not contribute to perception of fattiness in contrast to oil droplets. The perception of fattiness was probably related to the film formation properties of oil. As a result, MWP in liquid emulsions were generally perceived as rough but not creamy. In the case of MWP-emulsion-filled gels, although the gel matrix restrained the lubrication function of MWP particles, it also masked the rough perception of big MWP particles. Due to the combined effect of both oil droplets and MWP particles, MWP in gels resulted in an overall positive effect on the creamy perception. We conclude that MWP contributes to fat-related sensations in a different way than oil does. The perception of MWP particles is related to the size of the particle as well as the properties of the surrounding matrix.
    Remote sensing of epibenhtic shellfish using synthetic aperture radar satellite imagery
    Nieuwhof, S. ; Herman, P.M.J. ; Dankers, N.M.J.A. ; Troost, K. ; Wal, D. van der - \ 2015
    Remote Sensing 7 (2015)4. - ISSN 2072-4292 - p. 3710 - 3734.
    bare soil surfaces - mussel beds - wadden sea - ecosystem engineers - intertidal flats - tidal flats - sar data - roughness - classification - moisture
    On intertidal mudflats, reef-building shellfish, like the Pacific oyster and the blue mussel, provide a myriad of ecosystem services. Monitoring intertidal shellfish with high spatiotemporal resolution is important for fisheries, coastal management and ecosystem studies. Here, we explore the potential of X- (TerraSAR-X) and C-band (Radarsat-2) dual-polarized SAR data to map shellfish densities, species and coverage. We investigated two backscatter models (the integral equation model (IEM) and Oh’s model) for inversion possibilities. Surface roughness (vertical roughness RMSz and correlation length L) was measured of bare sediments and shellfish beds, which was then linked to shellfish density, presence and species. Oysters, mussels and bare sediments differed in RMSz, but because the backscatter saturates at relatively low RMSz values, it was not possible to retrieve shellfish density or species composition from X- and C-band SAR. Using a classification based on univariate and multivariate logistic regression of the field and SAR image data, we constructed maps of shellfish presence (Kappa statistics for calibration 0.56–0.74 for dual-polarized SAR), which were compared with independent field surveys of the contours of the beds (Kappa statistics of agreement 0.29–0.53 when using dual-polarized SAR). We conclude that spaceborne SAR allows one to monitor the contours of shellfish-beds (thus, distinguishing shellfish substrates from bare sediment and dispersed single shellfish), but not densities and species. Although spaceborne SAR cannot replace ground surveys entirely, it could very well offer a significant improvement in efficiency.
    Voor hoeveel natuur is er ruimte in de uiterwaarden?
    Querner, E.P. ; Makaske, B. - \ 2013
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 46 (2013)3. - ISSN 0166-8439 - p. 34 - 35.
    uiterwaarden - rivierengebied - hoogwaterbeheersing - vegetatie - ruwheid - stroming - hydraulische weerstand - modellen - river forelands - rivierengebied - flood control - vegetation - roughness - flow - hydraulic resistance - models
    In het kader van het programma Ruimte voor de Rivier worden grote delen van de uiterwaarden langs de Rijn en de Maas op een meer natuurlijke manier beheerd. Gemaaid grasland maakt plaats voor ruig terrein. Dat leidt echter ook tot minder capaciteit voor doorstroming bij hoogwater. Wordt dat laatste effect niet overschat?
    Sediment discharge division at two tidally influenced river bifurcations
    Sassi, M.G. ; Hoitink, A.J.F. ; Vermeulen, B. ; Hidayat, H. - \ 2013
    Water Resources Research 49 (2013)4. - ISSN 0043-1397 - p. 2119 - 2134.
    depth-integrated model - open-channel flow - suspended sediment - settling velocity - secondary flow - load transport - boundary-layer - particles - suspension - roughness
    [1] We characterize and quantify the sediment discharge division at two tidally influenced river bifurcations in response to mean flow and secondary circulation by employing a boat-mounted acoustic Doppler current profiler (ADCP), to survey transects at bifurcating branches during a semidiurnal tidal cycle. The ADCP collecting flow velocity and acoustical backscatter data was used to quantify suspended sediment discharge, adopting a recently introduced calibration procedure. Measured profiles of flow velocity and sediment concentration allowed us to compute spatiotemporal distributions of the shear velocity, the roughness length and the Rouse number. Spatiotemporal distributions of the settling velocity were obtained by combining the Rouse number and shear velocity estimates with in situ measurements from a laser particle size analyzer. Bed-load transport rates were inferred from shear stress estimates. The concentration field shows a direct response to bed shear stress, stressing the alluvial context of the system. The flow in the bifurcation regions is characterized by counter rotating secondary-flow cells, which stretch over the full width and depth of the cross sections in the downstream branches, and persist throughout the entire tidal cycle. The pattern of secondary flow suggests the flow approaching the bifurcation is concentrated in two independent threads. A two-cell structure inhibits the exchange of sediment that would occur in case a single cell would stretch over the full channel width. The division of suspended sediment primarily depends on the upstream transverse profile of the suspended sediment concentration, which is in turn dependent on geometrical factors such as upstream curvature.
    Verkenning van stromingsweerstanden : de hydraulische ruwheid van enkele natuurlijke uiterwaardvegetaties
    Querner, E.P. ; Makaske, B. - \ 2012
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2355)
    waterstromingsweerstand - uiterwaarden - vegetatie - natuurontwikkeling - hoogwaterbeheersing - waterbeheer - ruwheid - water flow resistance - river forelands - vegetation - nature development - flood control - water management - roughness
    Om de veiligheid tegen overstromingen in het rivierengebied te waarborgen is een goede doorstroomcapaciteit van het zomer- en winterbed van belang. Rivierkundige maatregelen, zoals uiterwaardverlaging en het graven van een nevengeul, kunnen de doorstroomcapaciteit verbeteren. Bij natuurontwikkeling, daarentegen, kan de afvoercapaciteit van de rivier afnemen door opstuwing als gevolg van een grotere stromingsweerstand. In dit rapport zijn drie alternatieve berekeningsconcepten voor het bepalen van de ruwheid van dergelijke vegetaties toegepast. De berekende ruwheden zijn vergeleken met de ruwheidswaarden die door Rijkswaterstaat (RWS) gehanteerd worden en die zijn vastgelegd in het handboek ‘Stromingsweerstand vegetatie in uiterwaarden’. Het blijkt dat bij de berekeningen voor een schematisch dwarsprofiel van de IJssel, de afvoercapaciteit berekend met het RWS-handboek voor de uiterwaarden tussen de 22 en 40% kleiner is dan ingeschat met de alternatieve berekeningsconcepten uit deze studie. In het handboek is voor relatief korte, natuurlijke uiterwaardvegetaties, zoals graslanden en ruigtes, de stromingsweerstand opmerkelijk hoog. Door kalibratie van de stromingsmodellen op het hoogwater van 1995 wordt het waterstandverlagende effect van lagere uiterwaardruwheden weer deels teniet gedaan, omdat de ruwheid van het zomerbed dan zodanig wordt aangepast dat de waterstand en de totale afvoer weer in overeenstemming zijn met de in 1995 bepaalde waarden. Deze handeling is ook uitgevoerd voor de drie alternatieve berekeningsconcepten. Er blijkt ook na kalibratie nog steeds een grotere afvoercapaciteit te zijn door een lagere inschatting van de ruwheid volgens de drie alternatieve berekeningsconcepten (tussen de 3 en 19%). Dit suggereert dat er meer natuurontwikkeling in de uiterwaarden toegestaan zou kunnen worden. Deze studie geeft geen aanleiding om andere concepten voor het berekenen van de afvoer te hanteren, maar geeft wel aan dat voor korte uiterwaardvegetaties, zoals graslanden en ruigtes, het handboek hogere weerstanden hanteert in vergelijking met de alternatieve berekeningsconcepten.
    Influence of spatial variations of microtopography and infiltration on surface runoff and field scale hydrological connectivity
    Appels, W.M. ; Bogaart, P.W. ; Zee, S.E.A.T.M. van der - \ 2011
    Advances in Water Resources 34 (2011)2. - ISSN 0309-1708 - p. 303 - 313.
    depression-storage capacity - overland-flow generation - tilled soil surfaces - water contamination - roughness - phosphorus - model - approximation - conductivity - variability
    Surface runoff on agricultural fields arises when rainfall exceeds infiltration. Excess water ponding in and flowing through local microtopography increases the hydrological connectivity of fields. In turn, an increased level of hydrological connectivity leads to a higher surface runoff flux at the field boundaries. We investigated the functional hydrological connectivity of synthetical elevation fields with varying statistical properties. For this purpose, we developed an object-oriented ponding and redistribution model to which Philip’s infiltration model was coupled. The connectivity behaviour is determined by the presence of depressions with a large area and spatial organization of microtopography in rills or channels. The presence of microdepressions suppresses the effect of the spatial variation of infiltration properties. Connectivity behaviour of a field with a varying spatial distribution of infiltration properties can be predicted by transforming the unique connectivity function that was defined for a designated microtopography
    Discharge estimation from H-ADCP measurements in a tidal river subject to sidewall effects and a mobile bed
    Sassi, M.G. ; Hoitink, A.J.F. ; Vermeulen, B. ; Hidayat, H. - \ 2011
    Water Resources Research 47 (2011). - ISSN 0043-1397 - 14 p.
    open-channel flows - shear-stress - sediment transport - secondary currents - velocity - roughness - sand
    Horizontal acoustic Doppler current profilers (H-ADCPs) can be employed to estimate river discharge based on water level measurements and flow velocity array data across a river transect. A new method is presented that accounts for the dip in velocity near the water surface, which is caused by sidewall effects that decrease with the width to depth ratio of a channel. A boundary layer model is introduced to convert single-depth velocity data from the H-ADCP to specific discharge. The parameters of the model include the local roughness length and a dip correction factor, which accounts for the sidewall effects. A regression model is employed to translate specific discharge to total discharge. The method was tested in the River Mahakam, representing a large river of complex bathymetry, where part of the flow is intrinsically three-dimensional and discharge rates exceed 8000 m3 s-1. Results from five moving boat ADCP campaigns covering separate semidiurnal tidal cycles are presented, three of which are used for calibration purposes, whereas the remaining two served for validation of the method. The dip correction factor showed a significant correlation with distance to the wall and bears a strong relation to secondary currents. The sidewall effects appeared to remain relatively constant throughout the tidal cycles under study. Bed roughness length is estimated at periods of maximum velocity, showing more variation at subtidal than at intratidal time scales. Intratidal variations were particularly obvious during bidirectional flow conditions, which occurred only during conditions of low river discharge. The new method was shown to outperform the widely used index velocity method by systematically reducing the relative error in the discharge estimates
    Evaluation of the Surface Energy Balance System (SEBS) applied to ASTER imagery with flux-measurements at the SPARC 2004 site (Barrax, Spain)
    Kwast, J. van der; Timmermans, W. ; Gieske, A. ; Su, Z. ; Olioso, A. ; Jia, L. ; Elbers, J. ; Karssenberg, D. ; Jong, S. de - \ 2009
    Hydrology and Earth System Sciences 13 (2009)7. - ISSN 1027-5606 - p. 1337 - 1347.
    land-surface - footprint estimation - temperature - atmosphere - models - area - roughness - index - soil
    Accurate quantification of the amount and spatial variation of evapotranspiration is important in a wide range of disciplines. Remote sensing based surface energy balance models have been developed to estimate turbulent surface energy fluxes at different scales. The objective of this study is to evaluate the Surface Energy Balance System (SEBS) model on a landscape scale, using tower-based flux measurements at different land cover units during an overpass of the ASTER sensor over the SPARC 2004 experimental site in Barrax (Spain). A sensitivity analysis has been performed in order to investigate to which variable the sensible heat flux is most sensitive. Taking into account their estimation errors, the aerodynamic parameters (h(c), z(0M) and d(0)) can cause large deviations in the modelling of sensible heat flux. The effect of replacement of empirical derivation of these aerodynamic parameters in the model by field estimates or literature values is investigated by testing two scenarios: the Empirical Scenario in which empirical equations are used to derive aerodynamic parameters and the Field Scenario in which values from field measurements or literature are used to replace the empirical calculations of the Empirical Scenario. In the case of a homogeneous land cover in the footprints of the measurements, the Field Scenario only resulted in a small improvement, compared to the Empirical Scenario. The Field Scenario can even worsen the result in the case of heterogeneous footprints, by creating sharp borders related to the land cover map. In both scenarios modelled fluxes correspond better with flux measurements over uniform land cover compared to cases where different land covers are mixed in the measurement footprint. Furthermore SEBS underestimates sensible heat flux especially over dry and sparsely vegetated areas, which is common in single-source models.
    Regional estimation of daily to annual regional evapotranspiration with MODIS data in the Yellow River Delta wetland
    Jia, L. ; Xi, G. ; Liu, S. ; Huang, C. ; Yan, Y. ; Liu, G. - \ 2009
    Hydrology and Earth System Sciences 13 (2009)10. - ISSN 1027-5606 - p. 1775 - 1787.
    surface-energy balance - time-series - vegetation - soil - algorithm - index - ndvi - temperature - evaporation - roughness
    Evapotranspiration (ET) from the wetland of the Yellow River Delta (YRD) is one of the important components in the water cycle, which represents the water consumption by the plants and evaporation from the water and the non-vegetated surfaces. Reliable estimates of the total evapotranspiration from the wetland is useful information both for understanding the hydrological process and for water management to protect this natural environment. Due to the heterogeneity of the vegetation types and canopy density and of soil water content over the wetland (specifically over the natural reserve areas), it is difficult to estimate the regional evapotranspiration extrapolating measurements or calculations usually done locally for a specific land cover type. Remote sensing can provide observations of land surface conditions with high spatial and temporal resolution and coverage. In this study, a model based on the Energy Balance method was used to calculate daily evapotranspiration (ET) using instantaneous observations of land surface reflectance and temperature from MODIS when the data were available on clouds-free days. A time series analysis algorithm was then applied to generate a time series of daily ET over a year period by filling the gaps in the observation series due to clouds. A detailed vegetation classification map was used to help identifying areas of various wetland vegetation types in the YRD wetland. Such information was also used to improve the parameterizations in the energy balance model to improve the accuracy of ET estimates. This study showed that spatial variation of ET was significant over the same vegetation class at a given time and over different vegetation types in different seasons in the YRD wetland
    Continuous measurements of discharge from a horizontal acoustic Doppler current profiler in a tidal river
    Hoitink, A.J.F. ; Buschman, F.A. ; Vermeulen, B. - \ 2009
    Water Resources Research 45 (2009). - ISSN 0043-1397 - 13 p.
    bed shear-stress - velocity distributions - probabilistic approach - fluid-flows - roughness - sediment - channel - adcp
    Acoustic Doppler current profilers (ADCPs) can be mounted horizontally at a river bank, yielding single-depth horizontal array observations of velocity across the river. This paper presents a semideterministic, semistochastic method to obtain continuous measurements of discharge from horizontal ADCP (HADCP) data in a tidal river. In the deterministic part, single-depth velocity data are converted to specific discharge by applying the law of the wall, which requires knowledge of local values of the bed roughness length (z0). A new filtration technique was developed to infer cross-river profiles of z0 from moving boat ADCP measurements. Width-averaged values of z0 were shown to be predominantly constant in time but differed between ebb and flood. In the stochastic part of the method, specific discharge was converted to total discharge on the basis of a model that accounts for the time lag between flow variation in the central part of the river and flow variation near the banks. Model coefficients were derived using moving boat ADCP data. The consistency of mutually independent discharge estimates from HADCP measurements was investigated to validate the method, analyzing river discharge and tidal discharge separately. Inaccuracy of the method is attributed primarily to mechanisms controlling transverse exchange of momentum, which produce temporal variation in the discharge distribution over the cross section. Specifically, development of river dunes may influence the portion of the discharge concentrated within the range of the HADCP
    Estimating Manning's n for steep slopes
    Hessel, R. ; Jetten, V.G. ; Zhang, G.H. - \ 2003
    Catena 54 (2003)39479. - ISSN 0341-8162 - p. 77 - 91.
    eroding rills - overland-flow - hydraulics - roughness - velocity
    Hydrological and soil erosion models require calculations of flow velocity, for which either the Darcy-Weisbach or the Manning equation is generally used. A series of field experiments was carried out in a small catchment on the Chinese Loess Plateau to obtain reliable values of Manning's n. The soils are typically erodible loess soils. The experiments were conducted for a range of land uses as well as for different slope angles (6¿64%). Measurements were performed on a 2.5×0.4 m plot, on which flow was allowed to find its own path. Water was evenly applied to the top of the plot and discharge, surface velocity, flow width and slope were measured. The results show that Manning's n can, just like Darcy-Weisbach f, be estimated from Reynolds number. Furthermore, for croplands, there is an apparent linear increase in Manning's n (and f) with increasing slope angle (R2=0.70). As Manning's n is usually assumed to be constant, this must mean that either velocity increases with slope or hydraulic radius decreases. The measurements showed virtually no increase in velocity and a minor increase in hydraulic radius with slope, as flow was more concentrated on steeper slopes. Possible explanations for this lack of increase in velocity include increased roughness [Water Resour. Res. 37 (2001) 791], decreased effective slope angle because of the development of vertical head cuts and a shift in energy use. All three hypotheses only apply to situations involving erosion. The trend of Manning's n with slope implies that, in soil erosion models using Manning's equation (or Darcy-Weisbach), the value of n (or f) should be a function of the slope for erodible soils. For non-erodible soil (as in woodland), no increase in Manning's n with slope was observed.
    Rustige of ruige omgang met varkens
    Mheen, H. van der; Spoolder, H.A.M. - \ 2003
    Lelystad : Praktijkonderzoek Veehouderij (Praktijkrapport / Praktijkonderzoek Veehouderij : Varkens ) - 26
    varkens - behandeling - ruwheid - dierenwelzijn - rundvleesproductie - dierverzorging - invloeden - pigs - treatment - roughness - animal welfare - beef production - care of animals - influences
    Uit onderzoek blijkt dat de interactie tussen mens en dier niet alleen het welzijn van de dieren, maar ook de productie ervan te kan beïnvloeden. Er is een onderzoek opgezet met als doel het toetsen van de hypothese dat gangbare verschillen in omgang met varkens de productieresultaten van de dieren, en de tijd nodig voor de controle van berigheid beïnvloeden. De conclusie luidt dat verschillende manieren van omgang met varkens, die langdurig worden gehandhaafd en die voor de praktijk herkenbaar zijn, een effect hebben op de productieresultaten van de dieren. Voor de praktijk hebben deze resultaten echter nog geen directe toepassingen. Blijkbaar is de benutting van de beschikbare energie bij de rustig behandelde dieren anders dan bij de ruig behandelde dieren. Rustig behandelde dieren houden blijkbaar meer energie uit het voer over, wat zich vertaalt in meer spekaanzet. De vraag is of we dit in een voordeel van de varkenshouder én het dier kunnen ombuigen. Hiervoor moet men onderzoeken of dieren die rustig worden behandeld zonder productieverlies met een andere, lager energetische voersamenstelling afkunnen
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