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Tracing of sediment transport has so far mostly been concentrated in rivers and particularly in estuaries and in shallow coastal waters with main interest on navigational, erosional and some pollutionary aspects. With the ever increasing oil activites in the North Sea, knowledge on bottom sediment movements at large water depths is becoming more and more important. Little tracing has been undertaken on the offshore sea bottom at depths exceeding 20 - 30 meters.

This paper is written in continuation of earlier published material (2, 4, 5) dealing with stability of tidal inlets on littoral drift shores. The experience available at that time was responsible for the introduction of two parameters: .vmean max/ defined as the mean max. velocity in the gorge at spring tide and the K/M-tot ratio (tidal prism at spring tide divided by material transport to the entrance from the adjoining shores) as the most pertinent parameters for description of overall stability. A more detailed justification for this choice is given in this paper, based on computation of the relative sediment transport at various tidal phases. Examples of earlier date (4) and twelve new examples from India are given.

Sediment transport in random waves at constant water depth is analyzed by dividing the flow field into two regions—the internal region and the boundary layer region. The suspension and transport of sediment in these two regions are treated separately. The total transport is then obtained as the total of these regions through matching boundary. In the bed layer, the load concentration is assumed to be proportional to the specific weight of the sediment and to the probability that the fluctuating lifting force exceeds the weight of the sediment. The bed load is then transported by the secondary flow (which is unidirectional) in the boundary. In the internal flow region, the sediment suspension is treated as a diffusion problem with the intensity of diffusion to be proportional to the amplitude of fluid particle motion. The transport velocity is assumed to be the same as the mass transport velocity of the wave. The predominant mode of transport is found to be suspended load. The total transport in a wind-generated wave field can be expressed as a power law of wind speed. For the case tested, the power should be of the order of 4.

A particular problem, of those arising in the economic development of estuary regions, concerns the maintenance and enlargement of navigation channels. The sediment transport plays an important role in connection with this problem. .Though the hydrodynamical processes are today, with the help of mathematical procedures, fairly exactly grasped, there is still insufficient knowledge about the related transport processes, the formation of ripples and dunes and of longterm periodical morphological changes. Nevertheless, the engineer wants information about sediment transport for his planning. A well-known aid is the movable bed hydraulic model, which has been technically developed to simulate the natural fluid-sediment interaction. Such models are not yet standard in hydraulic research institutes and. furthermore, they are not easy to handle. This is probably due to a lack of suitable similarity criteria for insuring valid experimental results. However, there exist recently developed somewhat compromised similarity relationships, which can be used for distorted movable bed tidal models. The experience gained with the movable bed. model Elbe I at the Bundesanstalt fur Wasserbau (BAW) in Hamburg provides an incentive for investigating special cases in other large tidal models of the German North-Sea coast. These models are presented in Fig. 1.

In this paper the practical design of coastal mobile bed models is considered. The semi-theoretical approach expressed by the author in earlier publications (9,10,11,12) is extended and used to classify and design coastal models. Fixed bed coastal models are discussed first to form a basis for the argument. Subsequently, mobile bed models are classified according to criteria of dynamic similarity satisfied in their design and scale effects present in their operation. Basic scale laws are next derived for all classifications of coastal models. This is done for both inshore and offshore models, the distinction being brought about by adjusting the velocity scales for unidirectional (and long wave) motion. Time and sediment transport scales are next derived and some well known models are compared. The presence of bedform and model distortion is also treated. The work is compared with that of other authors.

The physical characteristics of estuarine sediments provide useful information about sediment sources, the nature of bottom surface stresses and sediment transport mechanisms. Changes in sediment composition and state are also useful indicators for estimating the effects of unnatural stresses on dependent chemical and biological activities. In this study, the changes in several sediment properties have been monitored for an isolated estuarine dredging project. The effect of estuarine hopper dredge activities has been evaluated for an Army Corps of Engineers project at Coos Bay, Oregon. The project included suction head dredging at a shoal area within the navigation channel and in bay spoiling at a deep section of channel one mile downstream from the dredge site. Core samples were taken five days before dredging and two, thirteen and seventy days after dredging at the dredge and spoil sites. Subsequent laboratory analysis of the core samples revealed that dredging induced redistribution of bottom sediments produced significant changes in several physical characteristics of the dredged material. Repeated resuspension of bottom sediments during the dredging and spoiling operations caused a net loss of fine grained sediments and light organic constituents. Several symptomatic changes were observed which validate this finding, including: an increase in median grain size and decrease in uniformity of dredge spoils due to loss of fine fractions; a decrease in volatile solids in the dredge spoils due to a net loss of organics; a decrease in porosity at the spoils site due to the ability of the coarse grain sediments to resist resuspension; and a decrease in hygroscopic moisture content due to loss of porous organics and silt-clay material from the spoils. Conditions following dredging were observed for a period of seventy days. Partial recovery of the sediment system was observed after two weeks with no further recovery in two months. The initial recovery came about due to the availability of local sources of resuspended sediment adjacent to the dredge site. This occured under low flow conditions in early fall. Complete recovery of the system was not observed and probably requires the relatively large sources of sediment which accompany heavy winter and spring runoff. Thus, the immediate effects of dredging may persist until the annual cycle of sediment erosion and deposition have occurred.

The wave-induced sand transport alongshore is investigated by an energy principle approach. Although the energy approach has been used before, this is the first application to comparing theory and measurements of the distribution of littoral transport along a line perpendicular to the beach. Bed load transport equations are formulated for outside and inside the surf zone. Sand transport data were collected in the field using bed load traps. Wave, tide, wind, and current information was collected simultaneously in order to verify the derived predictive equations for longshore current and sediment transport. Quite reasonable predictions are obtained for the relative distribution of bed load transport, both inside and outside the surf zone.

Influence of grain size in sediment transport depends on flow conditions For bed load transport a maximum probably exists for load discharge as a function of gram size The important parameter seems to be the ratio To/T between the threshold shear stress and the flow shear stress.

Sediment transport In the vicinity of inlets and coastal regions depends on the combined bottom shear stresses due to both currents and waves. The modeling of the movement of bedload is controlled by the Proude law, bottom shear stress, wave steepness, and friction factor. Assuming Einstein's theory of bedload function can be applied to this study, an analysis was performed after conducting experiments in the flume and model basin. A series of results obtained from the flume tests is to Insure the relationship between the fluid characteristic and the movement of bedload. The final results concerning the longshore sediment transport appeared satisfactory with the estimated curves. The bottom configurations in the Inlet after each test were also shown satisfactorily similar. The sedimentologlcal time scale for the three bed materials were not In satisfactory agreement, however, more discussion of the results was presented in this paper.

Simultaneous field measurements of the energy flux of breaking waves and the resulting longshore transport of sand in the surf zone have been made along three beaches and for a variety of wave conditions. The measurements indicate that the longshore transport rate of sand is directly proportional to the longshore component of wave power.

A mathematical model is developed to calculate the amount of bottom sediment moved by wave action. The simplified case of a horizontal bottom and spherical material of uniform size is presented here; however, with some further groundwork it is thought that the model may be extended to actual field conditions without too much difficulty.

Experiments were made to determine the relative effects on the friction factor of a flow of the suspended sediment load and the configurations which form on sand beds of streams. Results showed that the friction factor of a stream carrying suspended sediment is less than a comparable one without sediment. They also showed that the reduction of friction factor due to changes in bed configuration is much larger than that due to suspended sediment.

The Depth sounding is the fundamental process for the investigation of sand drift on sandy beach and has been carried out by means of echo-sounders. Although it is necessary to obtain the actual variations of bottom topography under the direct action of strong waves, the data even by the up-to-date method of soundings are limited to the case of calm sea conditions. Moreover, even in calm seas it is often difficult to measure the depth of water in the surf zone which has remarkable change of bottom topography due to wave action. The author has no information on the data of bottom topography under the direct action of waves on actual beaches in Japan, excepting those of Mr. Fujiki on the coast of Niigata along the Japan Sea, who, however, had measured the bottom profile along one fixed line which was set perpendicularly to the beach. At present we have no effective method of measuring the amount of drift sand, and therefore the measurement of dynamical variation of bottom topography is considered to be the possible primary and fundamental approach to the estimation of sand drift on sandy beach without any coast structure and also to be the final method of finding out the similarity law between model test and actual phenomena, through which model test may become a confiderable method of solving the sand drift problem. In order to observe the dynamical varation of bottom topography by wave action, it is necessary to develope newly any possible method without boat and echo-sounder. This is the purpose of study of projection type sounder.

Tidal flow and suspended-sediment discharge were measured in or near the inlet to Bolinas Lagoon through seven ebbtides and six floodtides. The highest flows and suspended-sediment discharges occurred during the major daily ebbtide. Most transported sediment was sand and most sediment deposited in the lagoon was sand. Computations from a relation of suspended-sediment discharge and tidal range indicated that the annual suspended-sediment discharge of ebbtides exceeded that of floodtides by 9,000 tons. The highest concentration of suspended sediment occurred near the east shore of the inlet, which is at the end of a sand spit. The measured volume of water moved by a tide ranged from 180 to 2,740 acre-feet and the maximum flow measured was 7,900 cubic feet per second. The highest average velocity for a measurement was 4.9 feet per second. The maximum average velocity in the inlet occurred within an hour after midtide during a floodtide and usually at about one-third tide during an ebbtide. The relation of average tidal velocity (ut) to tidal range (R), was ut = 1.21R'50°; the average flow for a tide can be estimated by multiplying this calculated average velocity by the average cross section of the inlet.

This paper summarizes the results of a continuing study at the hydraulic laboratory at the University of California at Berkeley on this subject, which is supported by the Coastal Engineering Research Center (CERC) and which has resulted over the years in the Theses of Huon ti (1954), M. Manohar (1955), G. Kalkanis (1957, 1963), M. M. Abou-Seida (1965), M. M. Das (1968) and is at this time being continued by T. C. Mac Donald. All these researchers have greatly contributed to the success of this work while the author was mostly responsible for the continuity of the study. The aim of the study was to see if it is possible to establish for the description and prediction of sediment transport by waves a general system of approach similar to that which the author published in 1950 under the title '.'The Bed-Load Function for Sediment Transport in Open Channel Flows". ( It was hoped at the time that many of the basic steps of such a description may at least be similar to those used for uni-directional flow. It became apparent that such similarities of approach were quite feasible; but another difficulty became apparent from the beginning. While in the uni-directional flow many details of the flow, such as velocity distributions, boundary layers and turbulence had been, studied and described previously, such knowledge was almost entirely lacking for wave motion. The first part of the study consisted entirely of hydraulic measurements and of their analysis. In order to determine the necessary scope of such hydraulic studies, the analogy with sediment transport in uni-directional flow was used. Some of the principles governing uni-directional flow transport are: 1. Sediment motion can be divided into bed-load motion or surface creep and suspension. 2. While moving as bed load, the particle weight is to a large part transmitted directly to the nonmoving bed, not to the flow. 3. The rate of bed-load motion is defined by the equilibrium exchange of sediment between the bed-load and the nonmoving bed. 4. This equilibrium gives a direct relationship between the sediment rate and the flow conditions near the bed, including the turbulence. 5. The flow condition near the bed can be predicted for a uni-directional boundary layer as a function of the bed shear and the bed roughness, only.

A sand transfer system that requires no surface impounding area and that can be installed and operated at low cost is proposed The system consists of a hydraulic jet assembly operating from the bottom of a sand crater A jet pump and suction mouth are located at the lowest point of a crater-like depression dredged into the sea floor The crater acts as a gravity-fed sink for sand and other cohesion I ess material, thus serving the dual purpose of a mechanism for collecting sand and a sub-surface impounding area for the accumulation of sand.

During the last two decades considerable progress has been made in analyzing the diffusion process in estuaries. Unfortunately, certain difficulties (e g prediction of diffusion coefficients) still prevent common application of the diffusion method An old technique, related to the diffusion concept, can however, frequently give useful information regarding constituent mixing and transport velocities in natural estuaries.

The Lower Fraser River, being continually developed for better navigation and larger port- facilities, is an area of active sedimentation. The dynamic processes influenced by river discharge, tides and winds are probably the most important factors in the transport and deposition of sediments in the estuary. The main part of the Fraser Estuary is vertically homogeneous (non-stratified) and the sediments are transported progressively seaward and are accumulated near the limit of net landward flow. The lower estuary is stratified and coarse sediments are trapped near the toe of the salt wedge while the fine sediments are carried seaward with the outflowing river water. The hydrometric and sediment survey of the lower Fraser River are described. Survey results are used in determining the sediment balance of the river reach. In the budget analysis, the river and estuary are divided into four consecutive reaches, the sediment discharges are subdivided to represent about 10 particle size ranges and the balance is then determined for each reach and particle size range. Conclusions are drawn with respect to the sediment transport and depositional characteristics, annual variations, and the agreement between the sediment entering the estuary and the sediment dredged.

Collective movements of sediment occur in the form of sand waves m the nearshore zone and affect beach topography to a significant extent. Bar-type sand waves move only in the onshore direction and account for various accretive profiles on the subaerial beach. When the beach is eroded, these sand waves are simply disintegrated on the subaerial beach, instead of migrating back in the form of sand waves. These characteristics of bar-type sand waves help explain dynamic behavior of beach profiles with respect to profile configuration, sediment storage, and beach width. Cusp-type sand waves are considered to be a product of interaction between longshore currents and an erodible bed. Their presence causes variability in beach profiles along the shore between those containing a prominent bar and those without a bar. Migration of these sand waves may well produce pulsational transfer of material along the shore.

Sediment pollution can be defined as the increase in sediment concentration, due to artificial infusion of sediment, to a level harmful to fish and plant life The coastal engineer may be called upon to evaluate the result of an artificial sediment influx in terms of characteristic parameters like concentration and turbidity and to determine eventual deposition areas of the sediment This paper describes the field investigations carried out to evaluate a case of sediment infusion in one of the estuaries on the U S east coast The sediment was discharged via a pipeline at a rate of approximately 10 lbs/sec Nearly all the released sediment was in the silt range In addition to the results of the field measurements a simple mathematical model is presented, describing the temporal and spatial distribution of the sediment in the resulting sediment plume.