Modeling studies of the far-field effects of tidal flat reclamation on tidal dynamics in the East China Seas Dehai Song a, b, * , Xiao Hua Wang a , Xueming Zhu c , Xianwen Bao b a School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Northcott Drive, Canberra, ACT 2600, Australia b Key Laboratory of Physical Oceanography, Ministry of Education, Ocean University of China, Qingdao 266100, China c Key Laboratory of Research on Marine Hazards Forecasting, National Marine Environmental Forecasting Center, Beijing 100081, China article info Article history: Received 30 March 2013 Accepted 20 August 2013 Available online 29 August 2013 Keywords: far-field effect tidal flat tidal energy tidal asymmetry reclamation abstract In recent decades, the reclamation of tidal flat carried out by the authorities around the Bohai Sea, Yellow Sea, and East China Sea (BYECS) has reached new heights as a consequence of significant economic expansion in the coastal areas. We are concerned that the tidal flat reclamation may have not only local but also far-field effects on tidal dynamics in the entire BYECS. Numerical study shows different tidal patterns due to tidal energy redistribution when tidal flats around the BYECS are removed, in which the tidal range and phase are changed, and the amphidromic points are displaced. Tidal flats provide storage and dissipation for tidal energy; the former is much more significant than the latter. Loss of these functions caused by tidal flat reclamation will induce a redistribution of the extra tidal energy. Furthermore, we show that far-field effects on tidal dynamics would be observed on the west coast of Korea following significant reclamation on the Chinese Jiangsu coast. In turn, reclamation on the west coast of Korea may generate the far-field effects on the Chinese coast. Reclamation in the BYECS can result in rise of tidal amplitude and onshore sediment transport. The former may enhance the coastal hazards such as storm surge, and the latter may result in severe siltation. Therefore, careful consideration must always be given to any proposed artificial changes to tidal flat, given the effects of these on both the local environment and further afield. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Tidal motion is one of the major dynamical processes in the East China Seas (the Bohai Sea, Yellow Sea, and East China Sea, BYECS), where the tidal dynamics are quite complicated and the tidal ranges relatively large. Since 1970s, numerical methods have been applied to study the tidal dynamics in the BYECS (e.g. Guo and Yanagi, 1998; Kang et al., 1998; Bao et al., 2001). However, the wetting and drying (WAD) is always assumed to be a peripheral process due to the sparse model resolution. Therefore, the role of tidal flats in the tidal system of the BYECS has never been studied. Hydrodynamic models with WAD simulation have already been applied to study estuarine process (e.g. Ip et al., 1998; Ji et al., 2001; Ertürk et al., 2002). The significance of the WAD process for coastal ocean systems has also been addressed by many researchers. For tidal dynamics, numerical experiments without the WAD process would either underestimate or overestimate the tidal elevation and tidal current (Zheng et al., 2003; Oey et al., 2007). In addition, Xue and Du (2010) found the WAD process enhances the mixing and entrainment processes near the estuary, which results in stronger tidal intrusions into the estuary. They also speculated that the WAD process can affect much larger areas than the inter-tidal zone, especially via river plumes that feed into coastal currents. Essen- tially, tidal flats in the numerical experiments without the WAD process had to be set to either water or land, both of which change the local geomorphology. However, in previous studies only the local- and regional-scale processes due to the local geomorphologic modification were examined (e.g. Picado et al., 2010; Min et al., 2011; Li et al., 2012). Hasegawa et al. (2011) found tidal energy extraction in the Minas Passage, Bay of Fundy would alter the tidal elevations and tidal currents throughout the Gulf of Maine. This is proposed as a “far-field” effect. Thus, we wondered if the tidal flat reclamation also has far-field effects on the tidal dynamics in the entire BYECS, although the total area of the tidal flats is rather small compared to that of the BYECS (less than 2% of the surface area). The land reclamation carried out by the authorities around the BYECS has reached new heights as a consequence of significant economic expansion in the coastal areas. For example, in 2000 the Shanghai municipal government in China proposed to reclaim * Corresponding author. E-mail addresses: dehai.song@adfa.edu.au, dehai.song@gmail.com (D. Song). Contents lists available at ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss 0272-7714/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ecss.2013.08.023 Estuarine, Coastal and Shelf Science 133 (2013) 147e160