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Influences of the waterway project in the Yangtze River Estuary on sediment transport
Published in Zhao-Yin Wang, Shi-Xiong Hu, Stochastic Hydraulics 2000, 2020
Zhou Jifu, Li Jiachun, Liu Hedong
The influence of the project on bed deformation is depicted in Fig. 3(b). Under natural conditions, sediment deposition takes place in the upstream reach (between W1 and W2) of the navigation channel because the over-shoal-flows deliver sediment loads from the shoals to the channel. Hence, regular dredging is necessary to maintain demanded depth. In the downstream reach from W2, the channel bed is rather stable. With the levees erected, bed aggradation still happens between the levees. But two mild troughs are found between groins N2 and S2 and N3 and S3, because the groins narrow cross sections and hence increase local velocity. In the reach between W2 and W4, little bed changes can be seen before and after the project. This is due to the fact that the project doesn’t influence flow patterns in this area very much.
Process-based approach on tidal inlet evolution – Part 1
Published in C. Marjolein Dohmen-Janssen, Suzanne J.M.H. Hulscher, River, Coastal and Estuarine Morphodynamics: RCEM 2007, 2019
D.M.P.K. Dissanayake, J.A. Roelvink
After feeding the created ‘shoal’ or ‘sediment wave’ migrates down. In the Rhine branches the celerity of this wave is in the order of 1 to 2km per year. The influence of feeding therefore only slowly expands in downstream direction. Schwerdtfeger (2004) has shown that consequently degradation in the Dutch Rhine can only be treated effectively when sediment nourishment is distributed over a sufficiently long section. After all, the sediment-transport gradient causing the degradation acts upon the river bed over a long distance. According to Schwerdtfeger the amount of feeding needed to fully compensate the degradation is in the order of almost 50% of the yearly sediment transport rate, i.e. about 200,000m3/yr or 7000 ton/week.
Coastal sediment management as a response to intensifying storms and sea level rise
Published in C. Patrick Heidkamp, John Morrissey, Towards Coastal Resilience and Sustainability, 2018
James Tait, Ryan Orlowski, Jessica Brewer, Matthew D. Miller
The town of West Haven, over the years, has undertaken repeated beach replenishment episodes in order to maintain its beaches. Most of the sediment emplaced has eroded and been transported elsewhere. In the case of Prospect Beach, much of that sand has ended up in a large and still growing sand shoal. In the case of the Sandy Point beaches, the sediment placed during replenishment has ended up contributing to a new spit. Current Department of Energy and Environmental Protection policies discourage mining sand from local nearshore areas because of concern for nearshore ecosystems. However, considering the importance of beaches and the costs of replenishment, rethinking these policies in favour of instituting regional and local sediment management practices may be in order.
Experimental study of the strength properties of soft cohesive sediment subject to mechanical vibrations
Published in Marine Georesources & Geotechnology, 2022
The test soil samples were soft cohesive sediments obtained from the shoal of the Hangzhou Bay (labelled as sediment A), the mouth of the Yangtze River (labelled as sediment B), the Huangpu River (labelled as sediment C), and the Yangcheng Lake (labelled as sediment D) in China. The cohesive sediments were dried in an oven at 105 °C for 24 h. The dried sediments were sieved through a 1.0 mm mesh to eliminate impurities such as fibers, small stones, and shellfish. The sediment samples were then analyzed using a BT-9300SE laser particle size distribution instrument, which measured the sediment particle size according to the principle of light scattering. The grain size distributions of the cohesive sediment samples are shown in Figure 1. The dried sediments were then mixed with varying amounts of water in a bucket using a blender to obtain homogeneous remolded sediment samples with predetermined water contents (ensuring uniformity of the test bed). The sediment samples were then placed in a test box and consolidated for approximately 4 h (Dong et al. 2022). The liquid limits of the test sediments were 53.5%, 38%, 31.8% and 28.2%, and the plastic limits of the test sediments were 22.5%, 19.6%, 15.6%, and 16.6%. The water content of the four cohesive sediment samples ranged from 30% to 70%, which is similar to the water content of certain natural fields (Kimiaghalam, Clark, and Ahmari 2016; Kamphuis and Hall 1983; Keller 1968). The primary physical properties of the sediment samples are presented in Table 1.
Low water level in the Selenga River and reduction of silica input to Lake Baikal
Published in Inland Waters, 2019
Larisa M. Sorokovikova, Irina V. Tomberg, Valery N. Sinyukovich, Elena V. Molozhnikova, Tamara V. Khodzher
The rise in nitrogen and phosphorus concentrations in the Selenga River caused these nutrients as well as phytoplankton abundance to increase in Lake Baikal. By the beginning of the 2000s, anthropogenic input of nitrate nitrogen into the lake from the Selenga River was 57% higher and inorganic phosphorus was 42% higher than in the 1950s (Sorokovikova et al. 2000). The input of phosphorus into the lake from surface waters and atmospheric precipitation doubled between the 1950s and 1990s (Sorokovikova et al. 2000), changing the biomass and community structure of the lake’s plankton. For example, in Southern Baikal, maximum algal biomass increased 24–35 times during the summer–autumn period of 1990–1997 relative to values in 1964–1974 (Izmest’eva et al. 2001), and average surface chlorophyll a concentrations in July–August increased 300% from 1979 to 2003 (Hampton et al. 2008). Moreover, the concentration of fine centric diatoms increased by an order of magnitude in the water of the Selenga River Shoal, an area located in the lake adjacent to the Selenga river mouth (Genkal and Popovskaya 2003).
Potential deposition of biogenic silica source sediment in the Paleo-Yangtze Grand Underwater Delta estimated with satellite remote sensing
Published in Marine Georesources & Geotechnology, 2018
Net primary production changes seasonally in the Paleo-Yangtze Grand Underwater Delta, generally smaller in winter and greater in spring. Net primary production in the Paleo-Yangtze Grand Underwater Delta in 2013 was utilized for illustrating seasonal variation in the Paleo-Yangtze Grand Underwater Delta. Five points (A, Radial Sand Ridge Delta of the northern Jiangsu Shoal; B, the mouth of the Changjiang River; C, east of the mouth of the Changjiang River; D, center of the East China Sea; E, north of Taiwan Island) were used to determine seasonal primary production variation, and it was found that seasonal patterns differed greatly. Two monthly peaks of primary production annually were found at sites of the mouth of the Changjiang River, east of the mouth of the Changjiang River, and the center of the East China Sea. One possible reason for this may be that these areas were affected by the Kuroshio Current. At sites of the Radial Sand Ridge Delta of the northern Jiangsu Shoal, primary production increased correspondingly with increases in water temperature. At the site of the north of Taiwan Island, primary production increased sharply in March, and then it decreased. It did not vary greatly in any other months.