An expression for the critical shear stress noncohesive sediment is derived from balance of forces on individual particles at surface a bed. The resulting equation, given grain size and density, depends near‐bed drag force, lift force to ratio, particle angle repose. Calculated values uniformly sized correspond closely those determined Shields' diagram. initial motion problem mixed sizes additionally relative protrusion grains into flow latter decreases when diameter moving grain, D , larger...

The wavelength, height, and steepness of ripples formed under oscillatory flows in flume field studies are reexamined to construct a simple accurate method predicting these ripple properties. Ripples with wavelengths proportional near‐bed wave orbital diameter (orbital ripples), predominant laboratory experiments, found have heights excess the thickness boundary layer. that roughly grain size nearly independent (anorbital which predominate field, at least several times smaller than layer...

At sites near the Brazos River, Texas, an iridium anomaly and paleontologic Cretaceous-Tertiary boundary directly overlie a sandstone bed in which coarse-grained with large clasts of mudstone reworked carbonate nodules grades upward to wave ripple-laminated, very fine grained sandstone. This is only sequence uppermost Cretaceous lowermost Paleocene that records about 1 million years quiet water deposition midshelf outer shelf depths. Conditions for depositing such layer at these depths are...

The equations of motion for a sediment grain near noncohesive bed and those the local fluid flow are combined to produce set differential that can be solved numerically describe trajectory saltating as function time. lift coefficient is based on reanalysis data produced by Chepil, other parameters problem using standard mechanical relationships; initial velocity position specified with separate model. heights resulting trajectories found significantly lower than available measurements would...

A model for the velocity field over a poorly sorted bed is derived herein and applied to flow in steep streams with coarse gravel beds. In such streams, large clasts often are comparable size stream depth act as obstacles flow. The effect of these on estimated by partitioning total stress, proportional depth‐slope product, into purely fluid component form‐drag associated around obstacles. An eddy viscosity closure used, length scale dependent both distance from boundary wake dimension....

Among the many diverse aspects of environmental science, none is more critical to future society and nature than water. Understanding role water on Earth making good decisions regarding conservation hydrological hazards depends learning fundamentals physical hydrology. This textbook, now in an expanded second edition, provides clearest opportunity for students absorb those fundamentals. Written at introductory level, Elements Physical Hydrology covers virtually every aspect this subject,...

Shallow coastal lagoons are environments where a dynamic equilibrium exists between water quality and seagrass cover. Dense canopies limit the resuspension of bed sediments thereby creating clearer column positive feedback for growth. Positive feedbacks often associated with existence bistable dynamics in ecosystems. For example, bare covered sediment could both be stable states system. This study describes one‐dimensional hydrodynamic model vegetation‐sediment‐water flow interactions uses...

Wave‐generated shear stresses are the main mechanism responsible for sediment erosion on tidal flats and regulate both concentrations in water column and, together with currents, export to salt marshes ocean. We present herein a simple method estimate potential shallow basins caused by wind wave events. The determines aggregate response of entire basin, combining framework contribution from different landscape units. is applied system along Eastern Shore Virginia, USA. Our analysis unravels...

A bed load transport model based on the mechanics of sediment moving by saltation yields predicted values flux as a function boundary shear stress, grain diameter and density. The parameters required to calculate (particle velocity, concentration, height layer) can all be determined from our model, which computes sequences trajectories individual saltating grains well concentration that flow support. latter is related momentum accelerating extract flow. Predicted curves vs. stress agree with...

Tidal oscillations systematically flood salt marshes, transporting water, sediments, organic matter, and biogeochemical elements such as silica. Here we present a review of recent studies on these fluxes their effects both ecosystem functioning morphological evolution marshes. We reexamine simplified model for the computation water in marshes that captures asymmetry discharge between ebb. discuss role storm conditions sediment tidal channels marsh platform. methods field instruments...

A variety of surface roughness characterizations have emerged from nineteenth and twentieth century studies channel hydraulics. When the water depth h is much larger than characteristic height k s , formulations such as Manning's n friction factor f can be explicitly related to momentum z o in log‐law formulation for turbulent boundary layers, thereby unifying definitions a given surface. However, when comparable (or even smaller than) need not valid. Using newly proposed mixing layer...

Several expressions for characterizing bed roughness produced by a layer of saltating sediment have previously been proposed, and another is presented herein. These relate the magnitude bottom to thickness near‐bed particles. In two previous studies, empirically set constant proportionality was determined using data which associated with forms had be calculated subtracted from total observed roughness, remaining being attributed load. this paper are tested against values in upper plane flows...

We investigated the size and shape of area on sediment surface, so‐called footprint, that contributes to flux in subaqueous eddy correlation measurements. Tracer tracking simulations were performed for a dissolved conservative tracer released from surface into current‐driven flow not affected by density stratifications waves. Simulations revealed footprint length ( l ) can be calculated as = −2.783 − 158.7 h + 159.2 2 120.8 log( z 0 (all units m) measurements heights between 0.05 0.3 m above...