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Sediment transport to the sea by rivers is crucial for the stability of estuaries and coasts. The Yangtze River, the largest river in China, like many large rivers worldwide, is experiencing a decrease in sediment load reaching the coast. However, the tidal flat around Qidong Cape, located at the entrance of the North Branch of the Yangtze Estuary, is undergoing extensive siltation. The source of this sediment is unclear. In this study, a sediment core was collected and the geochemical characteristics of rare earth elements (REE) were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The results indicate the following: (1) The average content of REE is 178.57 μg/g, and the average ratio between LREE and HREE is 8.66, which is comparable to sediments from the South Yellow Sea. The chondrite-normalized and UCC-normalized patterns resemble those of the Yangtze River and the South Yellow Sea, indicating a negative gradient, a weak Ce-negative anomaly, and a distinct Eu-negative anomaly. (2) The continental shelf deposits in eastern China are primarily derived from sediment flux delivered by rivers. The sediments in the South Yellow Sea mainly originate from the Yangtze River and the Yellow River, exhibiting characteristics of a mixed source due to long-term geological processes, namely geochemical processes. The REEs in the tidal flat around Qidong Cape inherit the source area's characteristics and originate from the weathering of upper continental rock in mainland China. Moreover, the tidal flat around Qidong Cape is influenced by both runoff and tidal actions, leading to strong land–sea interactions and reducing the environment, explaining the Eu-negative anomaly. (3) Hydrodynamic forces in the North Branch of the Yangtze River have shifted from runoff to tidal dominance since the 1930s. However, marine hydrodynamics outside the estuary have remained unchanged. Consequently, the Subei coastal current plays a key role in sediment transport and diffusion. Sediments from the south wing of the Radiative Sand Ridge in the South Yellow Sea are transported southward by the Subei coastal current, and under tidal influence, suspended sediment is deposited in the tidal flat around Qidong Cape. Therefore, the sediment source has gradually shifted from the Yangtze River to the South Yellow Sea. [ABSTRACT FROM AUTHOR]

There is currently little understanding regarding storm surge in New Zealand, particularly in the southern region. To date, there has been no attempt to establish the frequency and magnitude of storm surge using observed sea level data on the open coast. The aim of this study is to examine the nature of storm surge in southern New Zealand and explore the influence of the Southern Annular Mode (SAM) and the El Nino Southern Oscillation (ENSO) on the frequency and magnitude of storm surge. Bayesian estimation is used through the 'extRemes' package in R to determine the return period for storm surge at three locations around southern New Zealand. The 100-year return level varied between 0.91 and 1.31 m. In addition, a statistically significant increase (2.88%) in storm surge intensity (SSI) on the south-east coastline was found. Applying cross-correlation to assess the response of SSI to ENSO and SAM, returned no detectable relationship, except a weak relationship between SAM and SSI on the south-east coast where a two-three month lagged response was present. [ABSTRACT FROM AUTHOR]

The increasing vulnerability of coastal mega-cities to storm surge inundation means both infrastructure and populations are subject to significant threat. Planning for further urban development should include consideration of the changing circumstances in coastal cities to ensure a sustainable future. A sustainable urban plan relies on well preparedness and prediction of future climate change and multiple natural hazards. In light of these needs for urban planning, this paper develops a general method to simulate typhoon generated storm surge at the meso-scale (1-100 km in length). Meso-scale simulation provides a general approach that could be implemented to fulfil the purpose of planning, and has relatively low requirements for computation time and data, while still providing reasonable accuracy. The case study of Shanghai was chosen to implement this method. The meso-scale simulated results of two historical typhoons not only provides a realistic result at the city level, but is also suitable for implementing a large amount of simulations for future scenario studies. The method is generally applicable to all coastal cities around the world to examine the effect of future climate change on typhoon generated storm surge, even where historical observed data are inadequate or not available. [ABSTRACT FROM AUTHOR]

This paper investigates bar migration in a fetch limited strong wind bay (Seaford Beach SE Australia). Onshore bar migration on open ocean beaches is dependant on long period swell wave and occurs during low energy conditions. However, in a fetch limited environment such waves are absent and most studies suggest that during low energy conditions the beach remains in an arrested state (Jackson et al. 2002). This paper spans a three month study period (15th March - 8th June 2008). Measurement of near shore morphology and wind data were collected. The two bars at Seaford behaved very differently; both onshore and offshore migration was detected during the three recorded storm events. The paper found that, firstly, wave breaking was incomplete in the middle bar during event 1 - the inner bar migrated offshore. Secondly wave breaking in the middle bar was almost complete during event 2 and the inner bar migrated onshore. Thirdly when wave breaking was complete in the middle bar during event 3 - the inner bar remained arrested on some profiles but bar height increased on others. The wave steepness threshold for onshore migration of the inner bar was parameterized s 0.041 - 0.042. Beach sediment modeling in fetch limited strong wind bays remains understudied. Our results should help to improve the predictive capability of beach sediment budgets in fetch limited strong wind bays. [ABSTRACT FROM AUTHOR]

Using micro-erosion meters (MEM) and traversing micro-erosion meters (TMEM), surface lowering rates of shore platforms on Kaikoura Peninsula, South Island, New Zealand have been measured over a total of 43 years. This record is the longest monitored network of this type. Since 1973, erosion rates have been calculated over two, two year periods 1973-1975, (n=31) and 1993-1996, (n=52) and at decadal scales; 1973-1993 (n=15), 1973-2003 (n= 12), 1973-2016 (n=7), 1993-2003 (n=50), 1993-2008 (n=34),, 1993-2016, (n=18). After 43 years, surface lowering rates remain similar to previously published rates at an average of 0.525 to 1.181 mm/yr. Statistical analysis shows that erosion rates over all measurement periods are derived from the same population. Thus short term rates derived from two years of monitoring remain indicative of decadal rates of erosion. Variations between measurement periods are best explained by the loss of the more rapidly eroding bolt sites. These losses point to the difficulty of maintaining monitoring over longer time scales. In November 2016 a Mw 7.8 earthquake raised the Kaikoura Peninsula approximately 0.8- 1 m, elevating much of the shore platforms above the tide range. This earthquake has reset the MEM record ending this long running erosion monitoring site of shore platform surface lowering. However the MEM network is now being used to monitor post-earthquake response of the uplift shore platforms and new marine terraces. [ABSTRACT FROM AUTHOR]

Wave propagation over shore platforms has mainly been investigated using single linear arrays of instruments deployed in a shore normal direction. This two-dimensional approach allowed basic understanding of wave breaking and dissipation but presents some limitations in term of nonlinear processes impacting wave propagation. The present research aims to revisit characteristics of wave propagation over shore platform in three dimensions. The focus is on the effects of platform morphology on wave directionality and energy as well as the behaviour of gravity and infra-gravity waves. High resolution data were collected for a month using a multi-dimensional array of 14 pressure sensors and two directional wave recorders (tritons) anchored to the platform, the largest field deployment yet accomplished on a rocky shore platform. Off shore incident wave height, period and direction were also recorded using an ADCP in 10 m of water 850 m from the study site. The deployment captured two storms and a spring/neap tidal cycle. Wave directional spectra were used to investigate directional shift between incident waves and waves propagating on the platform. The directional analysis shows up to a 80° shift between off shore and onshore waves. The observed wave direction on the platform corresponds mainly to the normal direction between the instrument and the concave platform edge indicating that strong refraction occurs at the edge. Non-directional spectra analysis was used to investigate the energy level of wind waves, gravity waves and infra-gravity waves over the entire platform. Results represent the variation of the energy of these three frequency bands in three dimensions over the entire platform. [ABSTRACT FROM AUTHOR]

A traversing micro-erosion meter has been fitted with an electronic digital dial gauge so readings can be logged to a laptop computer. This facilitates rapid collection and analysis of data of erosion rateson shore platforms. Data analysis is enhanced by using 3-D plotting software to calculate volumes of material being eroded and to investigate processes of erosion. [ABSTRACT FROM AUTHOR]