· · · Repository Hydraulic Engineering Reports

Een kortdurende, (zeer) zware (noord-)noordwesterstorm over de noordelijke Noordzee veroorzaakte aanzienlijke verhogingen van de waterstanden. Sinds de middelbare stormvloed van 28 januari 1994 was de waterstand bij Hoek van Holland niet meer zo hoog geweest. Tijdens het passeren van de stormvloed zijn de stormvloedkeringen in de Oosterschelde en de Hollandse IJssel gesloten. Het waarschuwingsbureau van de SVSD is geopend geweest van zaterdagavond 20 dec 23h00 t/m maandagmorgen 22 december 01h30.

Lecture notes provided for IHE on sediment transports

lecture notes on sediment transport by currents, initiation of motion, fall velocity, properties of the material, bed load, suspended load, total load, stable channels, river bed variations, scour, measuring techniques, sediment transport in pipes.

In the following paper, a brief summary is first of all given of the results and interpretation of tests already made known in former publications of the Laboratory for Hydraulic Research and Soil Mechanics at the Federal Institute of Technology, Zurich. After that, an attempt is made to derive an empirical law of bed-load transport based on recent experimental data. We desire to state expressly that by bed-load transport is meant the movement of the solid material rolling or jumping along the bed of a river; transport of matter in suspension is not included.

The distribution patterns of bottom sediment in Brunswick Harbor and vicinity, Georgia, reflect the long-term hydrodynamic response and generally correlate with dynamic factors affecting edimentation. Certain diagnostic minerals reflect the source area and are used as "natural tracers" to delineate direction of sediment movement. Analysis of sedimentary parameters also enables interpretation of direction of sediment transport. The results of this investigation indicate that shoaling presently occurring in Brunswick Harbor is related to materials from a source in the Altamaha River. Sediment contribution to shoaling is introduced into the harbor through the tidal inlet between the barrier islands and from the MacKay River during greater than average discharge rates of the Altamaha River. Shoaling rates in the harbor also correlate with discharge rates of the Altamaha River. This investigation demonstrates the value of sediment interpretation, based on knowledge of regional geology, to provide a basis for analysis of sediment movement in a coastal area. In such a complex coastal area as Brunswick, Georgia, the sediment characteristics augment hydraulic measurements and enable a more complete interpretation of the hydrodynamics involved. Such information has application to engineering design of coastal structures.

The distribution and dispersal patterns of sand-size particles has been investigated along a portion of the California coast south of San Francisco. The effectiveness of long-term, net littoral transport in the area has been evaluated through hydrodynamic considerations and through considerations of the dispersal patterns of sand. The distribution and dispersal patterns presented are based upon results of a vector analysis of the raw heavy mineral da ta, Four sedimentary provinces have been delineated. One blankets the continental shelf in the area studied and represents premodern sediment deposited during the last major regression and transgression of the sea. The remaining three represent Holocene deposits on the pre-modern sediment. The latter are only of local extent and are contiguous with their sources. These mineralogical changes along the coast preclude the existence of net littoral transport under present conditions. This conclusion agrees well with that predicted by hydrodynamic considerations. The contrasting picture presented by the widespread, relatively homogeneous pre-modern province and the localized, varied Holocene deposits is pximarily due to changes in littoral transport attendant with the rise in sea level to its present position.

This report presents an edited collection of memoranda prepared over the past forty years on several aspects of inlet hydraulic and sedimentary characteristics, and is being published because of its general value to the GITI, as well as for its potential use in stimulating other researchers studying tidal inlets.

This report shows the results of a detailed analysis of the various littoral processes which affect the California Coast between Pismo Beach and Santa Barbara. The method involves the concept of a sand budget based on the transport rates of all significant littoral processes. Each process is examined to assess the sedimentary contributions (credits) and losses (debits). To balance the sediment transports, the region is subdivided into five cells, the boundaries of which are chosen at positions where the longshore transport of sand has been estimated. Using basic data from maps, surveys, aerial photographs, climatic records, and wave conditions, the authors have determined a quantitative transport rate for each process in each cell. The results are shown in graphic and tabular form. The budget concept provides a practical tool for coastal engineering problems. However, the difficulty of moving from qualitative trends to quantitative determinations reveals gaps in the present state of knowledge and requirements for further research.

The suspension of sediment particles by turbulent eddy diffusion in a non- uniform flow region was studied, using the convective-diffusion equation as a mathematical model. A simplified form of the equation for which mixing characteristics and flow velocities 'vere assumed uniform was found to accurately describe the sediment concentration profiles which had been measured in a 24-foot long flume. The experiments also showed that turbulent mixing was more uniform than predicted by existing theories, and that it depended on the geometric characteristics of the mobile, wavy bed. Although diffusivities in the non- uniform region tended towards uniformity with downstream distance the vertical diffusive transport rate was related to depth as a power law function. An expression with analytic support was derived for the diffusion coefficients as functions of sediment and hydraulic variables.

Samenvatting van Japans onderzoek onder leiding van Horikawa en Homma in de periode 1960-1970

Lecture note for the international course.

The shoreline of Monterey Bay is beached over most of its length. The beach is essentially continuous except for the northern and southern ends of the bay which are characterized by numerous pocket beaches separated by narrow cliffed areas which extend to beyond the low water level. There appears to be no large supply of sand to the beaches at present as the rivers entering the bay are, with few exceptions, flooded estuaries that are ponded up to 20 miles upstream from the shore of the bay. It is probable that this 30 mile stretch of shoreline has reached a state of equilibrium under present hydrodynamic conditions. The present study is of a preliminary nature and was undertaken to determine if a static equilibrium does exist, if there is any significant transport along the shores of the bay, and to delineate what are the littoral transport patterns, if any. The approach used has been that of a heavy mineral study of the sand sized particles in the beach samples collected. Samples were grouped on the basis of their contained heavy mineral suites and in this manner large sedimentary provinces were delineated on the basis of similarity of heavy mineral composition. The relationships between the various provinces and between the provinces and physiographic features has been used to determine the littoral transport patterns and their relation to present conditions.

Sand transport processes and sediment and bedform dynamics are reviewed with emphasis on the measured processes on the shoreface between the seaward edge of the surfzone and the upper continental shelf on time scales from seconds to a year. The studies reviewed here were done off California, in the northern Gulf of Mexico, at Nova Scotia, on the Ebro delta, at Duck, New Jersey, southeastern Australia and New Zealand, and in the North sea off the UK, Belgium and the Netherlands. Each environment has its own specific forcings and processes, which emphasises the need for long-term synchronous field measurements of various parameters at the site of interest. In general, bedload transport is more important than suspended load transport except during severe storms or swell. Various types of ripples prevail, but in the heavy storms the (transition to) upper plane bed states do occur at water depths far beyond the depth of morphological closure of the surfzone. The number of studies is sufficient to identify a number of shortcomings of present knowledge: i. for the shoreface conditions, shear stress and hydraulic roughness models give widely varying results and have not been tested and calibrated a range of datasets; this leads to high uncertainties concerning the bed shear stress components for sediment transport; ii. there are many environments in which neither waves nor currents dominate but interactions between waves and currents are not well understood; iii. there is no concensus on definitions of bedforms and states, especially in conditions with both waves and currents; in addition the genesis of a number of bed states is not well understood; iv. coastal, near-bed density-driven currents derived from riverine fresh-water outflow can cause a net shoreward current with a potentially first-order effect on annual sediment transport, but this effect has not been quantified empirically; v. the exchange of sediment between surf zone, shoreface and shelf may be important for coastal sediment budgets on longer time scales (decades), but virtually nothing is known about the magnitude and the direction of the net exchange (for different grain sizes); vi. there are very few datasets with measurements of both bedload and suspended load transport and hydrodynamics at high near-bed resolutions, and none that allow the probabilistic integration to annual transport on the shoreface.

Analysis of the effect of a submarine canyon on the coastal erosion near Cap Lopez, Gabon, using mathematical modelling

Overview of sediment transport formulas and comparison with measurements in Waal and Rijn river in the Netherlands.

Depuis une vingtaine d'annees, les mangroves du Sénégal ont intéressé beaucoup de pédologues. Les etudes commencées par J.VIEILLEFON en 1965 ont été développées par C.MARIUS de 1971 à 1983. Conjointement a ces travaux, dans lesquels l'accent est mis sur les facteurs principaux de la pedogenese de ces sols, tels que le soufre et les sels, un contrat du C.N.R.S. (ATP "Vasières et mangroves", dirigée par J.LUCAS) a permis d'effectuer des forages profonds en Casamance, Gambie, Saloum et dans le delta du fleuve Sénégal. L'analyse pédologique de ces prélèvements a été faite par MARIUS (1978), tandis que les analyses minéralogiques et géochimiques ont été effectuées par Y.KALCK (1978) qui a esquissé la paléogéographie du golfe de Casamance au Quaternaire récent. Ce mémoire est consacré a l'étude sédimentologique des mangroves de l'estuaire de Casamance. Celle-ci est essentiellement menée à partir des analyses granulométriques de detail de sédiment provenant de sept sondages situés d'aval vers l'amont de l'estuaire. La première partie de ce memoire présente la zone estuarienne et ses caractéristiques géographlques et géologiques, ainsi que la localisation et les descriptions pétrographiques, texturales, minéralogiques et géochimiques des sept sondages. La deuxième partie est consacrée a l'analyse granuiométrique et expose successivement : - le principe de la méthode des indices d'évolution granuiométrique de RIVIERE ; - les techniques d'analyses granulomécriques et tout particuliérement une étude comparative et critique de trois méthodes d'analyse de la fraction fine (<50 pm) d'un sédiment ; - les données des analyses granulométriques et leur interprétation; Une troisième partie contient les résultats des observations morphoscopiques et exoscopiques des quartz des dépots de mangrove. Les formations de mangrove sont ainsi définies comme étant des sédiments très fins, souvent même très argileux et dont les phases quartzeuses ont des caractéristiques exoscopiques qui relatent les différentes évolutions subies par le dépôt.