Showing papers on "Siltation published in 1978"

Longshore sediment transport data: a review

Abstract: Siltation rates anticipated at harbor entrances, in navigation channels and at inlet structures as well as possible adverse effects caused by these and other coastal engineering constructions are often assessed based on considerations of longshore sediment transport rates. The ability to predict the longshore sediment transport rate is consequently of considerable importance in many coastal engineering problems. The engineering need for an ability to predict longshore sediment transport rates is evidenced by the fact that the development of empirical relationships preceeded, by decades, any attempts at rigorous analyses of the mechanics of sediment transport processes in the surf zone. A predictive relationship for longshore sediment transport rates, which enjoys considerable popularity in the United States, is the empirical relationship suggested by the U.S. Army (1973), Coastal Engineering Research Center (CERC) in their Shore Protection Manual (SPM-73).

A conceptual model of a siltation system in shallow lakes with littoral vegetation

Abstract: SUMMARY In shallow lakes a siltation system develops when wind driven water turbulence erodes the lake floor, silt is resuspended and transported by means of waterdrift into the littoral vegetation. Here, due to the resistance of the vegetation, the turbulence is reduced and the silt deposited. Through this mechanism, the prevailing winds have a major role in the erosion and siltation pattern, lake morphology, vegetation pattern and in the mixing of water and nutrients from the open water and the reedswamp and vice versa. The model explains the uneven distribution of vegetation at the lakes Neusiedlersee (Austria) and Chilwa (Malawi) satisfactorily, if one assumes a positive correlation between siltation and reedswamp growth and spread.

Tidal sedimentation in gros-cacouna harbor

Abstract: The harbor of Gros-Cacouna on the South shore of the St. Lawrence Estuary has been silting at the rate of 31 cm/yr. since it was dredged at the depth of 14 meters in 1968. Measurements of temperature, salinity, turbidity, current speed and direction were carried out as well as bottom sampling and reflection seismic profiling. A model of suspended sediment transport combines the tidal volumes and the current profiles at the harbor entrance. During a period of high turbidity (Spring) in the St.Lawrence Estuary, 54.2 tons of suspended sediments entered the harbor during the flood phase, while 41.1 tons were carried out during the ebb phase of a semi-diurnal tide, leaving 13.1 tons of sediments in the harbor. The transfer coefficient is 0.24 indicating that one quarter of the suspended sediment load settles in the harbor during one tidal cycle. In September, the turbidity is low in the Estuary and the suspended sediment budget in the harbor is 4 times smaller but the ratio of deposited sediments versus the total quantity of sediments transported in suspension is the same.