Holocene sea level changes and coastline snitts in Zhejiang Province, China

In the present paper, the Holocene sea level changes and coastline shifts in Zhejiang, China are discussed, based on the ancient coastline evidence related with sea level changes and 21 14C dat-ings of shell, peat or mud and wood samples along the Zhejiang coast. The development of Zhejiang coastline during the Holocene period can be divided into four stages. A lot of data of historical period and modern times have shown that tracing coastline shifts back to its source, we have to consider tremendous effects of man's activities besides natural factors, such as elevation and subsidence of the earth crust, sea level changes, supply of sediment, and littoral hydrodynamics.

Spatiotemporal Variations and Driving Factors of Coastline in the Bohai Sea

The utilization and protection of coastlines play a crucial role in the sustainable development of coastal cities.The coastline designations in recent years have witnessed more coastal areas worldwide undergoing significant land reclamation for agriculture,industry,and urbanization purposes.This study used remote sensing images from 1986 to 2016 to analyze spatiotemporal changes in the coastlines of 13 cities around the Bohai Sea,which cover one city(Tianjin City)and three provinces(Liaoning,Hebei,and Shandong).Using coastline and socioeconomic data from 1986 to 2016,a partial least-squares regression(PLSR)model was established to analyze factors affecting the utilization of coastlines in each city.The results showed that from 1986 to 2016,the retention rates of natural coastlines in the cities around the Bohai Sea decreased,and the overall coastline expanded toward the sea.Furthermore,the impacts of human activities were prominent on the silty mud and sandy coastlines.Economic development,population growth,and urbanization were the main drivers of the development and construction of coastal cities,which changed the coastlines around the Bohai Sea to a state of high-intensity use.In addition,national macro policies and the external market environment indirectly drove the intensity of coastline use through regulations and interventions in cities.However,there were significant differences in the levels of development of the cities surrounding the Bohai Sea.In the future,the differences in the original coastal resources and urban development planning must be considered,the traditional parameters of economic development must be changed,the efficiency of coastline utilization must be improved,and urban clusters must be integrated.

DEPOSITIONAL CHARACTER AND SHORELINE CHANGES OF THE NANDUJIANG DELTA,HAINAN ISLAND,CHINA

The Nandujiang delta dates from at least 3000 yr ago and probably was fomred earlier during the Holocene. The present delta is built up of plain, channels, lagoos, spits, coastal barriers and beaches.Tidal currents are directed approximately east-west. The dominant waves come from NNE and are locally generated. Erosion occurs mainly on the east side of the delta. As the delta was growing outward into deeper water, the influence of marine processes increased and the delta changed from a river-dominated delta. Former branches were closed by littoral drift. The recent reduction in sediment suppy from the river, caused by the construction of a reservoir, has led to erosion of the coast. Three coastal sections of the delta are discussed in detail. Erosion mainly taks place on the foreshore and spits and barriers migrae inland covering former lagoon deposits. Measures to reduce further erosion and landward migration of the coastline are needed.

Assessing the vulnerability of changing coasts,Hainan Island,China

Knowledge of coastline changes and vulnerability is of great importance to local government departments that are responsible for the management and development of coastal zones.To study the nature of change and vulnerability along the coasts of the Hainan Island,we collected a large number of sediment samples through the last few years,and reconstructed the changes of the coastline by combining the data of sediment grain-size analysis and the nautical charts/TM RS imaginary.Contrary to being almost free from erosion（as expected from the findings that the coastlines are in a relatively stable state）,four major cities in Hainan（i.e.,Haikou,Wenchang,Sanya and Changjiang） turned out to be suffered from a moderate coastal vulnerability primarily because of the large populations that impose considerable pressure on the coastlines.Thus,the assessment methodology utilized in this study,including both anthropogenic and natural factors,serves as a useful tool to obtain a comprehensive understanding of coastline vulnerability for local government,in terms of coastal management and adaptation.

Methodological study of coastal geological hazard assessment based on GIS

The current researches on risk assessment of geological disasters mainly focus on unexpected disasters such as collapses, landslides and mud-rock flows etc. As the convergence zone of land and sea, coastal zone is the most active and complex area of interactions of lithosphere, hydrosphere, atmosphere, biosphere and anthroposphere. The ecological environment of coastal zone is very fragile, so further systematical research on coastal geological hazard assessment and prevention is in urgent need. The author begins with the definition and research contents and selects three typical coastal geological disasters, namely, the seawater intrusion, coastline change and sea-level rise as the objects of study. The systematic analysis and study on assessment system and methods are conducted, hazard assessment factors are selected, and a completely set of coastal disaster assessment system is established based on the technique of GIS. We took Bao’an District of Shenzhen City as an example and carried out a case study.

Recent changing patterns of the Changjiang(Yangtze River) Estuary caused by human activities

To evaluate the controlling factors for coastline change of the Changjiang（Yangtze River） Estuary since 1974,we extracted the mean high tide line from multi-temporal remote sensing images that span from 1974 to 2014 at 2-year intervals.We chose 42 scenes to constrain the changing pattern of the Changjiang Estuary coastline,and implemented GIS technology to analyze the area change of the Changjiang（Yangtze） Subaerial Delta.Runoff,sediment discharge and coastal engineering were withal considered in the analysis of the coastline changes.The coastline has transgressed seaward since 1974,and a part of it presents inter-annual variations.The area of the Changjiang Subaerial Delta increased by 871 km2,with a net accretion rate of 21.8 km2/a.Based on the change of sediment discharge due to the major projects in the Changjiang River Basin,we divided the changing pattern of the coastline into three stages：the slow accretion stage（1974–1986）,the moderate accretion stage（1987–2002）,and the rapid accretion stage（2003–2014）.Liner regression analysis illustrated that there is a significantly positive correlation between the area changes and sediment discharge in the Chongming Eastern Shoal and Jiuduansha.This suggested that sediment load has a fundamental effect on the evolution of the Changjiang Estuary.Construction of Deep Waterway in the North Passage of the Changjiang River（1998–2010） led to a rapid accretion in the Hengsha Eastern Shoal and Jiuduansha by influencing the hydrodynamics in North Passage.Coastal engineering such as reclamation and harbor construction can also change the morphology of the Changjiang Estuary.We defined a contribution rate of area change to assess the impact of reclamation on the evolution of Changjiang Estuary.It turned out that more than 45.3% of area increment of the Changjiang Estuary was attributed to reclamation.

Numerical Simulation and Risk Analysis of Coastal Inundation in Land Reclamation Areas:A Case Study of the Pearl River Estuary

Coastal inundation results in many human casualties and significant economic losses.In this study,an inundation model with an unstructured mesh was developed using the ADvanced CIRCulation(ADCIRC)and Simulating WAves Nearshore(SWAN)models to simulate 43 inundation events from 1998 to 2018.A combined wind-pressure field derived from the assimilation windpressure model was used to drive the coupled ADCIRC-SWAN model.On the basis of the model results,a sensitivity study of the influence of land reclamation on coastal inundation was conducted.The results of the study showed that coastline changes caused by reclamation significantly influence the distribution of coastal inundation,particularly in areas where narrow waterways,bays,and peninsulas are newly formed.Combining the extreme inundation events calculated using the Gumbel and Weibull distributions,the 10-year,50-year,100-year,and 200-year return coastal inundations were obtained for the Pearl River Estuary in China.The risk of coastal inundation was analyzed according to the probability of the inundation depth exceeding 1 m.A hazard grade zoning map was drawn to guide disaster relief and mitigation in the reclamation area.

人类活动对港湾岸线及景观变迁影响的比较研究——以中国象山港与美国坦帕湾为例（英文）

Using multitemporal Landsat TM/OLI images at a 10-year interval, in this study, we （1） extracted information of spatial location, length, and sinuosity of coastline and landscape configuration, diversity and fragmentation in the bay areas of Xiangshan Bay （XB）, China and Tampa Bay （TB）, USA from 1985 to 2015; （2） constructed indices of artificial coastlines and human disturbance on bay area landscapes; and （3） explored and discussed the impacts of human activities on changes of coastlines and landscape types in the two bay areas. Our analysis results demonstrate the following five points. （1） During the past 30 years, the lengths of natural coastline in XB and TB shrank, while the lengths of their artificial coastline increased first and then maintained stable. Since there were different influences of human activities on coastlines and landscape types between the two bay areas, XB experienced dramatic changes in parts of coastline geomorphologies and continuous decrease of coastline sinuosity, while, in TB, there was a little change in coastline geomorphologies and its coastline sinuosity was almost unchanged. （2） The intensity of human activities in XB was continuously enhanced from 1985 to 1995, and then the degree of enhancement had slowed down after 1995. However, in the time period, the impacted extent of human activities gradually increased and finally covered almost entire coastlines in XB. In TB area, although the intensity of human activities was enhanced, the degree of enhancement slowed down from 1985 to 2015 and the impacted areas of human activates were concentrated in several coastal city areas. （3） The average area of landscape patches strongly disturbed by human activities in both XB and TB generally showed a trend of decreasing from 1985 to 2005. However, during the period of 2005 to 2015, the average patch area of landscapes disturbed by different degrees of human activities in XB changed differently, while in TB it almost did not change. （4） From 1985 to 2005, the indices of landscape diversity in various areas of human disturbance in XB gradually increased, while in TB, changes in indices of the landscape diversity varied. From 2005 to 2015, the changes in the intensity of human disturbance in both bay areas were from weak to strong, whereas the indices of landscape diversity in XB and TB increased first and then decreased. （5） The landscape fragmentation index in different human disturbance areas in both XB and TB gradually increased from 1985 to 2005, while from 2005 to 2015, in both bay areas, the landscape fragmentation index presented a decreasing trend.