Comparison and investigation on tidal levels designed for the coastal embankments in Guangdong-Hong Kong-Macao Greater Bay Area

Tidal levels designed for coastal levee in Pearl River estuary have been provided by Department of water resources of Guangdong Province in 2002 and played important role in ensuring the security of coastal cities in recent decades. However, big changes have taken place in the hydrological regime of the estuary as the sea water level rise and Frequent storm surges in recent years. The proportions of the coastal levee lengths in Guangzhou and Zhuhai city occupied a large part of the portion in the Bay Area, about 30% and 23% respectively, while the shortest in Shenzhen city, accounting for only 5%. The designed tidal levels used for coastal levees in the past were compared with those proposed by PRWRC in the year 2011, showing lower about 0.2∼0.5m totally in the mouths and open waters including Shiziyang of the estuary. It would reach to about 0.6∼0.7m lower in the waters around Nansha district after considering the influence of the typhoon Mangkhut and Hato, while there was little variation in the net river area upstream in any case. The controlled tidal levels designed for coastal levees were analyzed for its applicability and it showed that those used in Guangzhou, Shenzhen and Jiangmen city meet the requirements and were somewhat lower in Dongguan, Zhuhai and Zhongshan city under variation of hydrological regime recently.