Abstract of the proposal

Coastal groundwater regimes have a significant impact on the environmental and ecological conditions in coastal areas. Groundwater and seawater are usually in constant communication due to tidal fluctuations. The groundwater head fluctuation caused by the tidal effect influences the stability of slopes and engineering structures along the coast. For many environmental and engineering problems it is important to understand the response of groundwater to tidal fluctuation of coastal water.

Since the 1950's, research on the dynamic interaction between groundwater and seawater has attracted much attention. In most of the previous studies, however, the geological system in the coast is simplified as a single confined or unconfined aquifer. Coastal areas usually consist of a multilayered aquifer system, with an unconfined aquifer above one or more confined aquifers. For example, the typical coastal geological system in Hong Kong has fill material, marine mud, alluvium and decomposed igneous materials. The fill material is usually a good unconfined aquifer, while the marine mud and alluvium sand may serve as a confining unit and a confined aquifer, respectively. The hydraulic characteristics of the coastal groundwater regimes may be misunderstood and significant errors may be introduced if such a system is treated as one single aquifer.

The objectives of this project are: 1) to explore the dynamic relation between seawater and groundwater by analysing the tidal cycle and the groundwater level in multilayered geologic formations near the coastline in Hong Kong, 2) to investigate the hydraulic interaction of the different layers in such a system, and 3) to estimate hydraulic parameters of some typical geologic materials along coastline by considering the fluctuations of groundwater levels caused by tidal effects. This research will provide valuable insights and important hydrogeological information for studying various environmental and engineering problems in coastal areas of Hong Kong.

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