Erosion laws published in the literature are not expressed in dimensionless forms. It should be recognized t h a t the results concern erosion at the end of the velocity steps, w h e n the excess s h e a r stress is small smaller t h a n 0. While sandy tidal embayments without fluvial feeders and with fixed boundaries may obtain dynamic equilibrium and remain open over long timescales, we hypothesize that an abundance of mud and eco-engineering species often culminates in continuous embayment filling with fine sediment and the growth of intertidal and supratidal areas, eventually resulting in closure of the embayment. A N A L Y T I C M O D E L I N G Several analytical multi-layer models have been presented in the literature to account for wave-bed interactions. The v a r i a t i o n of Xcmw i t h ~g is observed to be non-monotonic and seemingly passes through a m i n i m u m , yielding values of Lm t h a t m a y at first be lower t h a n those for sand 0. S e d i m e n t analysis performed by de Croutte et al.
Journal of Geophysical Research, 98, 7039-7047. This was a t t r i b u t e d to the large values of the Richardson n u m b e r in our e x p e r i m e n t s because the bed was consolidated. At noted, because in n a t u r e wave p a r a m e t e r s change very slowly w h e n compared to the time scale of rheological a d j u s t m e n t , we can a s s u m e equilibrium between forcing e. Hence the phase shift 5, also called loss angle, can characterize the state of liquefaction of mud, provided one considers liquefaction as a rheological evolution of m u d due to s t r u c t u r a l b r e a k down t h a t allows the m a t e r i a l to approach viscous behavior. Here we will deal with a simplified t r e a t m e n t of a bed characterized by two grain populations, one fine and the other coarse. Furthermore, models are necessarily oversimplified because of the limitations in computer capacity on the one hand, and on the other h a n d the impossibility to account for the complexity of the very non-homogeneous and variable composition of n a t u r a l cohesive sediments. It is an introductory treatment, suitable for a first course in coastal and estuarine processes for earth scientists or engineers.
British Library Cataloguing in Publication Data A catalogue record from the British Library has been applied for. Linearized calculation for a stratified mud layer. From an analogy with salt-fresh w a t e r stratified flows, a saturation concentration is defined as the m a x i m u m sediment load t h a t can be carried by t u r b u l e n t flow. For cohesive muds, since a gradual pore pressure buildup does occur, fluid mud generation is likely to take place more readily t h a n implied by 2. Flume studies of the transport of sediment in estuarial shoaling processes. A poster session has been scheduled in the second week of the summer school. Gdotechnique, 49 6 , 709-726.
Settling and consolidation of mixtures of cohesive and non-cohesive sediments. Since the actual normal and shear contact forces s u r r o u n d i n g a particle in a cohesive bed can be considered to be r a n d o m l y directed as a first order approximation, they will be assumed to have no tangible effect on bed liquefaction. It is conceivable t h a t in the mild wave environment of Lake Okeechobee under fair weather conditions, scale effects are in fact not too significant. Thesis, University of Florida, Gainesville. We assist in establishing the basis for a long-term planning and development of activities, by taking into account land use and adaptation to the effects of climate change. Therefore a unifying theory for sedimentation and self-weight consolidation has been developed Toorman, 1996 and 1999a.
Thesis, University of Utrecht, Utrecht, The Netherlands, 488p. I N T R O D U C T I O N This study was motivated by the observed erosion under wave action in the Seine estuary in F r a n c e. Prentice-Hall, Englewood Cliffs, New Jersey. Drag reduction also implies that, for the same energy input, the depthaveraged flow rate can increase and the total transport of sediment can be much higher t h a n anticipated, certainly when concentration effects on the bottom shear stress are neglected as in traditional models. The interplay between fresh and salt waters is agitated by tides and topography, which together make estuaries amongst the most dynamic and fascinating marine systems on earth.
In: Advances in HydroScience and Engineering, S. Cohesive sediment transport modeling: European perspective E. Shallow stratigraphy of Lake Okeechobee, Florida: a preliminary reconnaissance. Threedimensional numerical modeling of cohesive sediment transport processes in estuarine environments. K D a t a indicate t h a t the erosion rate decreases exponentially with time while the excess s h e a r stress decreases toward zero.
Because the estuary is open westward, which is the direction of the most frequent winds, waves are very often able to penetrate the estuary and erode sediments deposited on tidal flats. Furthermore, it has become clear t h a t the bed strength is time dependent due to densification by self-weight consolidation, thixotropy, creep, dynamic loading by waves and tides, mass exchange with the water column due to erosion and deposition and biological activity. Since the effect of gas on the viscoelastic p a r a m e t e r s may not be captured easily through rheometry, such effects could render the model results qualitative. Coastal and estuarine zones are particularly sensitive to pressure from climate drivers, population and increasing exploitation of resources. Box 1207 Hangzhou, 310012, Peoples Republic of China liyanC~nail. Journal of Hydraulic Engineering, 117 9 , 1184-1194. A recent series of m e a s u r e m e n t s at four semi-permanent anchor stations on either side of the Maasgeul, the access channel to the port e.
The procedure must be used for different materials and for different forcing conditions in order to fully describe non-linear wave mud interactions, including dispersion and damping of waves, onset of liquefaction and critical scales of the problem time, depth, wave amplitude etc. The definition of R is quite specific. It is e s t i m a t e d t h a t the contribution of waves to the vertical mixing is about 20%, implying t h a t the suspension is close to its s a t u r a t i o n value. Again, sediment compaction in the lower deltaic plain of the Bengal Basin covering entire Sunderbans and wasting away of peat accelerate the subsidence. The critical shear stress is shown to decrease exponentially with increasing specific gravity of mud particles and the water content of the mud layer, and is further shown to asymptotically approach the critical stress of noncohesive particles when the water content increases.