Atilla Bayram

Cross-shore distribution of longshore sediment transport: comparison between predictive formulas and field measurements

Abstract The skill of six well-known formulas developed for calculating the longshore sediment transport rate was evaluated in the present study. Formulas proposed by Bijker [Bijker, E.W., 1967. Some considerations about scales for coastal models with movable bed. Delft Hydraulics Laboratory, Publication 50, Delft, The Netherlands; Journal of the Waterways, Harbors and Coastal Engineering Division, 97 (4) (1971) 687.], Engelund–Hansen [Engelund, F., Hansen, E., 1967. A Monograph On Sediment Transport in Alluvial Streams. Teknisk Forlag, Copenhagen, Denmark], Ackers–White [Journal of Hydraulics Division, 99 (1) (1973) 2041], Bailard–Inman [Journal of Geophysical Research, 86 (C3) (1981) 2035], Van Rijn [Journal of Hydraulic Division, 110 (10) (1984) 1431; 110(11) (1984) 1613; 110(12) (1984) 1733], and Watanabe [Watanabe, A., 1992. Total rate and distribution of longshore sand transport. Proceedings of the 23rd Coastal Engineering Conference, ASCE, 2528–2541] were investigated because they are commonly employed in engineering studies to calculate the time-averaged net sediment transport rate in the surf zone. The predictive capability of these six formulas was examined by comparison to detailed, high-quality data on hydrodynamics and sediment transport from Duck, NC, collected during the DUCK85, SUPERDUCK, and SANDYDUCK field data collection projects. Measured hydrodynamics were employed as much as possible to reduce uncertainties in the calculations, and all formulas were applied with standard coefficient values without calibration to the data sets. Overall, the Van Rijn formula was found to yield the most reliable predictions over the range of swell and storm conditions covered by the field data set. The Engelund–Hansen formula worked reasonably well, although with large scatter for the storm cases, whereas the Bailard–Inman formula systematically overestimated the swell cases and underestimated the storm cases. The formulas by Watanabe and Ackers–White produced satisfactory results for most cases, although the former overestimated the transport rates for swell cases and the latter yielded considerable scatter for storm cases. Finally, the Bijker formula systematically overestimated the transport rates for all cases. It should be pointed out that the coefficient values in most of the employed formulas were based primarily on data from the laboratory or from the river environment. Thus, re-calibration of the coefficient values by reference to field data from the surf zone is expected to improve their predictive capability, although the limited amount of high-quality field data available at present makes it difficult to obtain values that would be applicable to a wide range of wave and beach conditions.

Experimental study of a sloping float breakwater

The aim of this study was to evaluate the performance of a sloping float (or inclined pontoon) breakwater with respect to expected wave climate for protection of small commercial vessels and yatch marinas. A two-dimensional model study was carried out for regular waves in intermediate water depths. The experimental results showed that the transmission coefficient was relatively insensitive to wave height and that it consistently increased as the wave period decreased. The performance of this type of breakwater was found to be promising for intermediate water depths.

Wave transformation in the nearshore zone : Comparison between a Boussinesq model and field data

Abstract A numerical model based on the Boussinesq equations was developed to simulate wave transformation in the nearshore zone with emphasis on describing the effects of wave breaking. Two different formulations for estimating additional momentum due to depth-limited wave breaking, namely one proposed by Watanabe and Dibajnia [Watanabe, A., Dibajnia, M., 1988. A numerical model of wave deformation in the surf zone. Proceedings of the 21st Coastal Engineering Conference, ASCE, pp. 578–587] and another one by Schaffer et al. [Schaffer, H.A., Madsen, P.A., Deigaard, R., 1993. A Boussinesq model for waves breaking in shallow water. Coastal Engineering 20, 185–202], were incorporated and tested in the numerical wave model. Detailed, high-quality data from Duck, NC, collected during the DUCK85 and SUPERDUCK field experiments using photographic means were employed to evaluate the applicability of the Boussinesq model to surf-zone conditions. Also, comparison with the field data allowed for an assessment of how well the two formulations could describe the effects of wave breaking on the evolution of the waveform. Model simulations were compared with measured time series of water surface elevation as well as with derived statistical quantities, such as the skewness, kurtosis and root-mean-square wave height. Overall, the model results were satisfactory, although the Boussinesq model failed to accurately reproduce the strong nonlinear shoaling that occurred prior to breaking. The roller model developed by Schaffer et al. produced somewhat better agreement with the data than the model proposed by Watanabe and Dibajnia. However, the difference was small and both formulations are judged to yield acceptable results, although improvements are needed before the predictions can be used for calculating the sediment transport rate in intra-wave models.

Performance of Longshore Sediment Transport Formulas Evaluated with Field Data

The skill of six well-known formulas developed for calculating the longshore sediment transport rate was evaluated in this study. Formulas proposed by Bijker (1967, 1971), Engelund-Hansen (1967), Ackers-White (1973), Bailard-Inman (1981), Van Rijn (1984), and Watanabe (1992) were investigated because they are commonly employed to calculate the time-averaged net sediment transport rate in the surf zone. Detailed, high-quality data on hydrodynamics and sediment transport from Duck, NC, collected during the DUCK85, SUPERDUCK, and SANDYDUCK field experiments were utilized to assess the predictive capability of these six formulas. Overall, the Van Rijn formula was found to yield the most reliable predictions over the range of swell and storm conditions that the field data covered. The Engelund-Hansen formula worked reasonably well, although with large scatter for the storm cases, whereas the Bailard-Inman formula systematically overestimated the swell cases and underestimated the storm cases. The formulas by Watanabe and Ackers-White produced satisfactory results for most cases, although the former overestimated the transport rates for swell cases and the latter yielded considerable scatter for storm cases. Finally, the Bijker formula systematically overestimated the transport rates for all cases. 1 Department of Water Resources Engineering, Lund University, Box 118, S-22100, Lund, SWEDEN. 2 U.S. Army Engineer Research and Development Center, Field Research Facility, 1261 Duck Road, Duck, NC, 27949-4471, U.S.A. 3 U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, 3909 Halls Ferry Road, Vicksburg, MS, 39180-6199, U.S.A.

Model Investigations on Wave Disturbance and Vessel Movements in Dawei Sea Port, Myanmar

This paper describes the use of numerical and physical modeling studies for the design of a new port on the southwestern coast of Myanmar. A series of numerical modeling scenarios was carried out to optimize the port layout including entrance channel with respect to wave penetration into the port, and to refine the design wave conditions for the sizing of the primary armor on the breakwaters. Wave conditions inside and outside the port were assessed using a two-dimensional Boussinesq wave model. As a part of design process, three-dimensional physical (scale) modeling studies were undertaken at the Canadian Hydraulic Centre (CHC) in Ottawa, Canada to refine and further optimize wave agitation and disturbance levels within the port basins. This paper focuses on the influence of the length of the main breakwater section on the wave conditions and downtime inside the port, and compares the results from the numerical and physical modeling.