Coastal changes in Hong Kong and Southern China

Abstract

This research examines past coastal changes and the possible impacts of future changes in southern China and Hong Kong. It aims to both assess coastal changes at a number of defined sites, and to examine more general trends in sea-level during the Holocene This provides a context within which impacts of future sea-level changes and marine flooding are examined. The methods used in this work may be divided into two broad categories. Sedimentary analysis, together with an examination of fossil diatom remains has revealed changes in the sedimentary history of three coastal lowland sites, and has highlighted significant changes in the palaeogeography of these sites. Evidence of former sea-levels lower than present mean sea-level has been found. The methods for this work are based on research carried out along many coasts around the world, but particularly in northwest Europe. This detailed stratigraphic analysis has not been applied to sites in southern China before. This study suggests that it could be used very successfully in the future. A Geographical Information System has been used to integrate a wide range of data on wastal lowlands to assess the possible risks and impacts of sea-level changes and marine flooding in southern China. This builds on the work on past sea-level changes. The method of analysis using the Geographical Information System was developed for this study. An analysis of coastal changes at three sites has been carried out, and the results of this are evaluated and discussed. A database of radiocarbon dated sea-level index points from southern China has been created from information derived from many published and unpublished sources. Theses data suggest that sea-levels rose rapidly from between 8000 and 5000 years B.P., and have then fluctuated around present mean sea-level. It is still unclear whether sea-levels have risen significantly above present levels for any prolonged period of time during the late Holocene. The analysis of possible impacts of future sea-level rise has shown that a large part of the Zhujiang delta is already at risk from any rise in sea-level of more than a few centimetres. A small part of the eastern part of the Zhujiang delta has been analysed in detail. This has demonstrated the potential for using a Geographical Information System to examine larger coastal areas. This study highlights the deficiencies in the data currently available, particularly from China and shows the potential for future work in this field. Sea-level have changed dramatically over a variety of timescales in the past, and the risks and impacts of any future rise in sea- level are considerable.