Occupying about 14% of the land area, China's estuary and coast supports more than 40% of the population and contributes to more than 60% of GDP. It is the frontier of China's economic and social development as well as reform and opening-up. Due to the high population density, shortage of land resources has become a major stumbling stone of regional development in estuarine and coastal areas. As a result, expanding development space by exploiting tidelands has become a significant measure to promote economic and social development. In the Twenty-First Century, China has successively launched and implemented a new round of coastal development strategy. Coastal areas have witnessed urbanization, industrialization and rapid population concentration, while local tidelands are developing intensively at high speed in vast areas and on a large scale. For example, the Caofeidian Industrial Zone, a national circular economy pilot zone, has taken up more than 300 km2. And according to planning, Tianjin Binhai New Area will see a reclamation area of 426 km2 by 2020. It is also proposed in Outline of Jiangsu Coastal Area Development Plan that by 2020 the reclamation area in the province will reach 1800 km2. The estuarine and coastal tideland development has become a national strategic demand.
Intensive tideland development may have major influences on the natural attributes of the sea area. It has great practical significance to scientifically and rationally develop and utilize tidelands so as to relieve the population-land contradiction in the estuary and coast areas and to promote social and economic development. While unordered large-scale development and utilization of tidelands may bring problems in multiple aspects including ecology, resource environment, flood (storm surge) disaster, economy and society. The key technical problems of estuarine and coastal tideland development and management include: dynamic evolution and resource characteristics of tidelands, hydro-sediment dynamics and geomorphological process, tideland development and shoreline utilization, and estuary management and storm surge disaster prevention and control in the circumstance of cluster development of tidelands.
1. Major Innovative Achievements
Theory and simulation technology of sediment transport under the influence of wave-current interaction have been developed and enriched.
1.1 The unified law of the Shields curve of sediment incipience under the influence of wave-current interaction has been revealed; and the formulas of cohesive fine grain sediment settling velocity in muddy estuary and coast as well as the distribution of sediment concentration in the waters of silt coast under wave breaking conditions established.
1.2. A series of expressions depicting wave breaking and velocity distribution under the influence of wave-current interaction have been proposed; and the key physical phenomena and dynamic mechanism of the horizontal distribution and profile changes of nearshore wave-induced current revealed.
1.3. A multi-factor complex dynamic geomorphic evolution simulation system of estuary and coast has been integrated and constructed, and the water and sediment transport and evolution of shoals and troughs in complex dynamic environment reproduced.
1.4. The influence mechanism of the distortion ratio on the similarity of estuarine and coastal model has been revealed, the similarity of sediment concentration and seabed topographic changes under the influence of wave-current interaction achieved, and the packaged technology of sediment movement physical modeling under the influence of wave-tide-current interaction independently developed.
The key technologies of comprehensive development and management of vast tideland and deep water shoreline have been proposed.
1.5. Combining the three of flood control in the Haihe estuary, comprehensive utilization of tideland, and siltation prevention and disaster reduction, a layout plan of estuary extension of the Haihe River in the circumstance of cluster development of tidelands has been put forward as the regulation line.
1.6. The stability evaluation of Caofeidian sand islands and deep troughs is the key to prove the development feasibility. The dynamic geomorphologic pattern and sediment transport model of Caofeidian have been summarized and analyzed, and the dynamic mechanism of tidal channels and the variation tendency of shoal and trough stability revealed. With the help of mathematical model calculation of compound dynamic geomorphology evolution and sediment physical model tests, the variation tendency of shoal and trough stability after implementation of main projects such as Caofeidian bank-linking dike and port area reclamation has been revealed.
1.7. The radial sand ridges in the South Yellow Sea have received much concern and once was considered as "forbidden zones" for port construction because of their special shapes, large scale and frequent activity. It has been proposed that the main cause of the southward movement of the radial sand ridges axis is the relative enhancement of rotational tidal waves caused by the coastal erosion of the abandoned Yellow River Delta. It has been proposed to control the erosive coast recession and to build the port by taking the tendency advantage of gradually close-to-shore deep water. It has been successfully applied in the construction of 100,000 dwt channel in the Binhai Port.
1.8. The rules of revetment wave runup and overtopping under the condition of wind, wave and tide combination have been revealed, and technical measures to control overtopping and effectively reduce the crest elevation put forward, solving the key problems of the storm surge defending and disaster reduction of newly built seawalls in large-scale tideland development regions.
The utilization plan and seawall construction program of China’s estuaries, coasts and tidelands has been completed.
1.9. For the first time, a clear picture of the resource reserve in estuarine and coastal tidelands as well as the existing problems in the process of tideland development and utilization have been found out. Within the five major national planning areas, the tideland area shallower than the 5m isobath consists of about 24.8 thousand km2, while that shallower than the 0m isobath is about 9307 km2.
1.10. The water function zoning of China’s estuaries, coasts and tidelands has been completed. The estuarine and coastal tideland utilization has been classified into protection zones, reserve zones and restricted utilization zones. Upon overall consideration of the requirements for estuarine flood (storm surge) control, waterlog drainage, navigation and eco-environment protection, the objectives and measures of estuarine and coastal tideland development and management have been proposed.
1.11. Upon overall consideration of coastal meteorology, hydrology, geology and other natural conditions, as well as requirements of regional economic and social development and the safe operation of major national economic facilities, China’s seawall construction scheme has been compiled, which regulates the standards of seawall construction, specifies the construction layout and timing of seawall in the 2015-2020 period, so as to guide seawall management.
2. Academic Outputs
50 papers were published, including 10 SCI papers, 15 EI papers and 2 software copyrights.
3. Application, Promotion, and Comprehensive Benefits
The main research results have been widely employed in the planning, design, development and construction of Tianjin Binhai New Area, Caofeidian national circular economy zone, coastal development in Jiangsu, HZMB artificial islands and other major national projects, working successfully in the practice of tideland utilization and seawall construction.
