THE DIFFERENTIAL SEDIMENTATION BETWEEN THE TWO SIDES OF THE PEARL RIVER ESTUARY IN THE LAST 5 000 YEARS AND ITS INFLUENCE ON THE URBAN AND INFRASTRUCTURE PLANNING OF HONG KONG
五千年来珠江口两岸沉积差异及其对香港城市和基础设施规划的影响

Having been formed when sea level reached the present level approximately 5 000 years ago, all the present-day estuaries are geologically young. The sharp contrast on the geomorphologic features between the two sides of the Pearl River Estuary is mainly the results of differential deposition. Each year approximately 80 million tons of suspended sediments are brought into the sea by the Pearl River through its eight outlets. Because of the geographical setting and Coriolis force most of the sediments are transported and deposited along the western side of the Lingdingyang Estuary including Macao and Zhuhai. Comparatively very few suspended sediments from the river reach Hong Kong crossing the Lingdingyang estuary. As a result, the Pearl River Delta along the west side of the Lingdingyang Estuary was developed in the last 5000years. With the continuously growth of the delta all the deep water bays were filled up by rapid sedimentation creating thousands of acres of productive land. At the mean time, the 870km coastline of Hong Kong gained almost no land from either the river or the sea. The coastline remains dominated by a ria form with numerous potential port sites. The result of the differential sedimentation has a profound influence on the urban and infrastructure planning of Hong Kong, especially in regard with the metropolis-harbor development. A brief investigation on the history of Singapore, Hamburg, Rotterdam, Guangzhou, Macao and other major cities with full scale sea ports reveals that there are connnonty three phases in the development of the metropolis-harbor relation. The general trend of this relation is towards the separation of the metropolis and the harbor. Hong Kong is a highly developed international city and Victoria Harbor is a full scale seaport. Many of the functional(traffic, residential and industrial) systems operating for the metropolis and the seaport overlap and interlock in a extremely limited space. This condition is responsible for many urban developing problems in Hong Kong. In the last decade, Hong Kong government carried out a series consultant studies on the urban and infrastructure planning. The "Port and Airport Development Strategy Studies" (PADS) propose and describe a most ambitious engineering project in Hong Kong's history. In this study a scenario analysis of the urban development of Hong Kong with regards to metropolis-harbor relation is conducted. The strategies proposed include combinations of choice for the siting of metropolis expanding and the new port. Two factors of the external environment considered in the analysis are: population growth and demands for expanding the port. The changes of the factors have been assumed under the "Trend" and "Accelerated". Four levels of qualitative criteria for population density, traffic condition, environment quality and city image are used to evaluate the outcomes of each strategic combination and external environment scenarios for the year 2001, 2030 and 2050