Hydraulic properties of biological crusts on sand dunes studied by 13C-CP/MAS-NMR : A comparison between an arid and a temperate site
Action biogène ; Allemagne ; Brandenburg ; Domaine aride ; Dune ; Eau du sol ; Encroûtement ; Etude comparée ; Géochimie ; Imperméabilité ; Infiltration ; Israël ; Negev ; Porosité ; Propriétés du sol ; Sable ; Sol ; Zone tempérée
Arid area ; Biogenic process ; Brandenburg ; Comparative study ; Dune ; Duricrust ; Geochemistry ; Germany ; Infiltration ; Israel ; Negev ; Porosity ; Repellency ; Sand ; Soil ; Soil properties ; Soil water ; Temperate zone
Using principal component analysis (PCA), the AA. studied the relationships between hydraulic properties and 13C-CP/MAS-NMR shift regions of biological soil crusts (BSCs) on sand dunes under arid and temperate conditions. The arid study site
was located near Nizzana, in the northwestern Negev, Israel and the temperate site was near Lieberose, Brandenburg, Germany. BSCs were sampled at each site near the dune crest, at the center of the dune slope and at the dune base. The soil texture was finer
and swelling. The findings support the hypothesis that hydraulic properties of BSCs are determined by extracellular polymeric substances (EPS) and soil texture. Hydraulic properties in BSCs result from the combination of chemical properties related to C
This paper presents an approach to incorporate time-dependent dune evolution in the determination of bed roughness coefficients applied in hydraulic models. Dune roughness is calculated by using the process-based dune evolution model of Paarlberg et
al. (2009) and the empirical dune roughness predictor of Van Rijn (1984). The approach is illustrated by applying it to a river of simple geometry in the 1-D hydraulic model SOBEK for two different flood wave shapes. The new approach helps to reduce
Litostratigrafie en hydraulische doorlatendheid van het freatisch reservoir te de Panne. (The lithostratification and the hydraulic conductivity of the unconfined aquifer at De Panne, Belgium)
Large bedforms and associated hydraulic conditions within microtidal-inlet channels, southern Gulf of St. Lawrence, Canada
Différents types de macroformes de litage, à deux échelles de grandeur (mégarides de sable, dunes) apparaissent dans les gorges des petits chenaux de goulets balayés par des micromarées. Les plus grandes formes (longueur 32 m et hauteur 1 m) restent
Complex confining layers. A stochastic analysis of hydraulic properties at various scales
This volume presents a study of the problem of characterizing the hydraulic properties, i.e. hydraulic conductivity and effective porosity, and ground water flow of complex confining layers at various scales. The study has shown that it is possible
to derive representative hydraulic properties at the scale of model blocks, from hydraulic properties measured at the score scale. - (AGD)
to represent soil characteristics of the study watershed. Also, the sampling data revealed that this watershed consists of 9 classes of landforms, namely mobile dune (MD), mobile semi-mobile dune (SMD), rolling fixed semi-fixed dune (RFD), flat sandy land (FD
[b2] Hydraulics Water Resources Lab., Dep. of Civil and Environmental Engineering, Old Dominion Univ., Norfolk, Etats-Unis
Chenal ; Cordon littoral ; Dune ; Etats-Unis ; Florida ; Géométrie hydraulique ; Hydrodynamique ; Inondation ; LiDAR ; Littoral ; Modèle ; Onde de tempête ; Ouragan ; Risque naturel ; Sable ; Saint Georges Island ; Télédétection
Channel ; Channel geometry ; Coastal environment ; Dune ; Florida ; Hurricane ; Hydrodynamics ; Inundation ; LiDAR ; Model ; Natural hazards ; Remote sensing ; Sand ; Sand bar ; Storm wave ; United States of America
as the critical velocity necessary to mobilize sand when a hydraulic connection between the watershed and back-barrier bay is present. Storms of moderate strength and rainfall intensity may be sufficient to keep the return channels open within the back-barrier
A partial explanation of the dependency of hydraulic conductivity on positive pore water pressure in peat soils
Part of the relationship between positive pore water pressures and hydraulic conductivity in peat soils may be explained by accumulations of methane bubbles. The AA. show how compression and expansion of gas bubbles with changes in pore water
pressure could cause changes in hydraulic conductivity and thus help to explain some observations of dependency of hydraulic conductivity in peats on pore water pressure. Consideration is also given to the effect on hydraulic conductivities of methane gas
Hydraulics of interrill overland flow on rough, bare soil surfaces
A set of laboratory experiments on bare, rough soil surfaces was carried out to study the relationship between soil surface roughness and its hydraulic resistance. A new model is developed to predict the hydraulic resistance of the surface, based
on detailed surface roughness data. Roughness profiles perpendicular to the flow are used to calculate the wet cross-sectional area and hydraulic radius given a certain water level. The algorithm of Savat is then applied to calculate the hydraulic resistance
Hydraulics of sediment-laden sheetflow and the influence of simulated rainfall
This paper evaluates and compares hydraulic characteristics in flows with and without rainfall disturbance. The spatial uniformity of simulated rainfall properties, and its significance to flow hydraulics, are also discussed.
Sustained storage and transport of hydraulic gold mining sediment in the Bear River, California
This study examines the large deposits of hydraulic gold mining sediment and reevaluates Gilbert's (1917) classic model of sediment transport in a symmetrical wave that is based on hydraulic mining sediment primarily in the Yuba Basin. Sustained
storage and transport of hydraulic mining sediment in the Bear Basin are documented and a revised model of sediment transport is proposed.
Flow-separation berms downstream of a hydraulic jump in a bedrock channel
The purpose of this paper is to report the first direct observation of the phenomenon of gravel berm formation, downstream of a hydraulic jump. As the observations were fortuitous, detailed measurements of hydraulic conditions were not possible
but estimates were obtained. These observations are compared with laboratory experiments and theory. The deposits have significance in constraining flood palaeoflow reconstructions as the presence of berms determines the former location of hydraulic jumps.
Estimating unsaturated hydraulic conductivity from easily measured soil properties
The authors measured hydraulic conductivity (saturated and unsaturated) on 127 soil cores, which were taken in different horizons of a wide variety of Belgian soil series. The hot air method and the crust method were combined to obtain the complete
range of hydraulic conductivity from saturation to air-dry. Regression equations for estimating the Gardner parameters were established from simple soil properties, such as soil texture, carbon content, bulk density. Three parameters can reasonably well
be estimated from the textural composition and the saturated hydraulic conductivity.
Salt effect on hydraulic conductivity of a vertisol
The changes in saturated hydraulic conductivity, macroscopic swelling and clay dispersivity of a sodic black clay soil in relation to solution concentration and Na adsorption ratio of the percolating solution were measured. Based on the threshold
concentration curves, an empirical relationship relating saturated hydraulic conductivity and soil solution properties has been derived for vertisols and its field applicability established. For all practical purposes, swelling of clay seemed to be the major
factor responsible for loss of saturated hydraulic conductivity of a sodic vertisol.
Discriminant function analysis of compositional data: an example from hydraulic geometry
Compositional discriminant function analysis of bank stability on the basis of hydraulic geometry had a success rate of 88%, making routinely archived measurements of stream width, cross-sectional area, mean velocity, and discharge a readily
Ungauged catchment modelling II. Utilization of hydraulic models for validation
This paper presents the second part of an exploration of the application of developments made in hydraulic floodplain modelling to ungauged flood forecasting. A two dimensional finite element model, RMA-2, is applied to a 25 km floodplain reach
Hydraulic conditions for rill incision under simulated rainfall : a laboratory experiment
A series of controlled laboratory experiments were conducted in order to obtain precise data on the hydraulic and sediment transport conditions during rill formation.
Logratio linear modelling of hydraulic geometry using indices of flow resistance as covariates
This study develops a statistical model for the relationship between channel friction and at-a-station hydraulic geometry, which presents potential difficulties with regard to both non-linearity and spurious correlation.