Anthropogenic sea level rise and adaptation in the Yangtze estuary
Heqin Cheng1, Jiyu Chen1, Zujun Chen2, Renliang Ruan3, Guiquan Xu2, Gang Zeng4, Jianrong Zhu5, Zhijun Dai1, Shenghua Gu6, Xianlin Zhang7 and Hanmei Wang8, (1)East China Normal University, State Key Labortary of Esturarine and Coastal Research, Shang Hai, China, (2)Shanghai Water Planning and Designing Research Insitute, Shanghai, China, (3)Shanghai Water Authority Bureau, Shanghai, China, (4)East China Normal University, School of City and Regional Science, Shanghai, China, (5)East China Normal University, State Key Labortary of Esturarine and Coastal Research, Shanghai, China, (6)Shanghai Hydrology Administration, Shanghai, China, (7)Shanghai City Planning and Land Resources Bureau, Shanghai, China, (8)Shanghai Insitute of Geological Survey, Shanghai, China
Abstract:
Sea level rise is a major projected threat of climate change. There are regional variations in sea level changes, depending on both naturally the tectonic subsidence, geomorphology, naturally changing river inputs and anthropogenic driven forces as artificial reservoir water impoundment within the watershed and urban land subsidence driven by ground water depletion in the river delta. Little is known on regional sea level fall in response to the channel erosion due to the sediment discharge decline by reservoir interception in the upstream watershed, and water level rise driven by anthropogenic measures as the land reclamation, deep waterway regulation and fresh water reservoir construction to the sea level change in estuaries. Changing coastal cities are situated in the delta regions expected to be threatened in various degrees.
Shanghai belongs to those cities. Here we show that the anthropogenic driven sea level rise in the Yangtze estuary from the point of view of the continuous hydrodynamic system consisted of river catchment, estuary and coastal sea. Land subsidence is cited as 4 mm/a (2011-2030). Scour depth of the estuarine channel by upstream engineering as Three Gauge Dam is estimated at 2-10 cm (2011-2030). The rise of water level by deep waterway and land reclamation is estimated at 8-10 cm (2011-2030). The relative sea level rise will be speculated about 10 -16 cm (2011-2030), which these anthropogenic sea level changes will be imposed into the absolute sea level rise 2 mm/a and tectonic subsidence 1 mm/a measured in 1990s. The action guideline to the sea level rise strategy in the Shanghai city have been proposed to the Shanghai government as (1) recent actions (2012-2015) to upgrade the city water supply and drainage engineering and protective engineering; (2) interim actions (2016-2020) to improve sea level monitoring and early warning system, and then the special, city, regional planning considering sea level rise; (3) long term actions (2021-2030) to implement both the safety and the transformation and development of the city.
