Effects of reclamation on hydrodynamics in the Shuanglong River Estuary

Huidi Liang, Cuiping Kuang, Jie Gu, Wei Chen, Xiaodan Mao, Honglin Song

Friday 3 july 2015

9:00 - 9:15h at Oceania (level 0)

Themes: (T) Managing deltas, (ST) Impacts of urbanization and land reclamation

Parallel session: 14K. Managing deltas - Impacts

Large-scale land reclamation usually results in significant alteration of topography, which may lead to changes of hydrodynamics in the tidal estuaries, thus finally affecting the geological or ecological evolution. Located in the west bank of Bohai Sea in the northeastern China, Caofeidian (CFD) is regarded as a ‘diamond’ harbor site for its natural deep waterway. From 2003, a large-scale reclamation was started in CFD to build the port, reaching up to 230 km2 in 2013. The Shuanglong River Estuary (SRE), a natural tidal estuary lying in the west of the CFD, was typically affected by the reclamation and construction in the CFD. Therefore, there is a practical need to investigate the influence of such morphological changes on the estuarine hydrodynamics. In this study, a 2D flow model based on MIKE 21 was set up to study the changes of hydrodynamics in the SRE before and after reclamation project. Model validation with observations indicates that the model simulation can well capture the regional patterns of tidal flow over the study area. Comparison of the water levels and tidal currents before and after the reclamation indicates that: 1) The high water levels are driven up by 0.08-0.21 m in the SRE after the reclamation without upstream flood discharge. However, the reclamation has little negative impacts on the flood discharge capacity of the Shuanglong River Channel. 2) The duration asymmetry of flood and ebb currents is alleviated in the channel, which is accompanied by the reduction of inequality between maximum current velocities. 3) As the reclaimed land cut off parts of the water exchange, the tidal current directions are parallel to the coastal line and the maximum flood and ebb flow velocities significantly decrease due to sand-excavating. In conclusion, the reclamation definitely affects the hydrodynamic process in the SRE, while the changes are far from threatening the coastal flood control safety. Besides, the alleviating inequality between flood tide and ebb tide is proved to be beneficial for maintaining the stability of the Shuanglong River Channel, which makes great sense to improve local navigation conditions.