The effects of hydrodynamic conditions on geotechnical strength of the sediment in Yellow River Delta

Coastal structures in tidal estuaries are of scientific and societal interest as they form important artificial sea barriers resulting in different hydrodynamic conditions on both sides of them. A field study was performed on both sides of an embankment in the Yellow River Delta, China, in order to investigate the temporal and spatial variations in the geotechnical strength of the sediment caused by the effects of different hydrodynamic conditions. Using a portable core penetration tester together with hydrodynamic observation and fractal dimension analyses, changes in sediment strength were tested in 1999 and 2002 in rectangular areas on both sides of the embankment and along two cross-shore profiles. The field observations both on space and time scales suggest that different intensity in wave loading can not change the mean strength of the superficial sediment within 0–15cm depth, but rather makes it more uneven under strong hydrodynamic conditions, with the increasing degree of heterogeneity that can be quantitatively described by the fractal method. The effect of waves is regarded as the major control factor on the quasi-periodic alternation of sediment strength within the study area surface and the depth stratification in the Yellow River Delta. Further work is still necessary to determine the forming process, its mechanism and their implications for efficient environmental management, coastal protection and hazard forecasting.