Preliminary assessment of the impacts of deep foundations and land reclamation on groundwater flow in a coastal area in Hong Kong, China

Many coastal areas have been intensively urbanized because people living and working on or near coastlines are increasing. Land reclamation from the sea and high-rise buildings are common approaches to satisfying the growing needs for more housing and other land use. Coastal areas are usually the ultimate discharge zones of groundwater systems. Using a coastal area in Hong Kong as a case study, this paper discusses the change in a groundwater system due to land reclamation and construction of building foundations in a coastal area. The upper part of the study area is in a nearly natural state, whereas the lower part is probably one of the most extensively developed areas in the world. It is evident that the groundwater flow system in this area has been changed over the last century. The piezometers in the transitional zone between the natural slopes and the urbanized areas indicate significant response to rainfall and obvious upward groundwater flow. To understand these piezometric responses to rainfall, a cross section is selected for detailed study using a two-dimensional multilayered numerical model. The parameters and structure of the aquifer system are calibrated by comparing the simulated and observed water levels. To reproduce the observed behavior of the groundwater system, the model has to include two important characteristics: a highly permeable zone at the rockhead and a reduction in hydraulic conductivity of 14–20 times in the urbanized area. The simulation demonstrates that both land reclamation along the coastline and deep foundations have contributed to the modification of the flow system, but the deep foundations have the most profound impact, especially when a high conductivity zone is present at the rockhead. R sum La plupart des zones c ti res ont t intensivement urbanis due la croissance de la population qui travaille et vive sur les zones littorales. La r cup ration des terrains sur la mer ainsi que la construction des grandes immeubles sont les moyens usuels utilis s pour satisfaire les demandes accrues de logement. D’habitude les zones c ti res repr sentent l’exutoire final des aquif res. En utilisant la zones c ti re de Hong Kong comme un tude de cas cet article analyse les changements dans les syst mes aquif res produits par la r cup ration des terrains et par les fondations des grandes immeubles. Tendis que la partie sup rieure de la zone tudi e se trouve presque l’ tat naturel, la partie inf rieure repr sente une des zones les plus d velopp e du monde. Il est donc vident que la circulation des eaux souterraines a t modifi e pendant le derni re si cle. Les pi zom tres remplac s entre les versants et la zone urbanis e montrent une r ponse significative aux pr cipitations ainsi qu’une hausse g n rale des niveaux. Pour mieux comprendre la r ponse des niveaux aux plues on a mod lis l’ coulement dans une coupe vericale en utilisant un mod le num rique multicouches. Les param tres et la strucure du syst me aquif re ont t cal s en comparant les niveaux calcul s et mesur s. Affin de reproduire les niveaux mesur s le mod le doit consid rer deux carat ristiques importantes: une zone p riglaciaire grande perm abilit et une diminution jusqu’ vingt fois de la perm abilit dans les zone urbanis es. La simulation a mis en vidence que les r cup ration des terrains au long du littoral aussi bien que les fondations profondes ont modifi l’ coulement mais que les derni res ont l’impact le plus important surtout lorsqu’il s’agit de la zone p riglaciaire grande perm abilit . Resumen Muchas reas costeras han sido urbanizadas de manera intensiva, debido a la presi n creciente de la gente que quiere vivir y trabajar en estos sitios. Los terrenos arrebatados al mar y los edificios de gran altura, son las respuestas comunes para satisfacer las necesidades de mas vivienda y usos nuevos para el suelo. Las reas costeras Received: 4 November 2003 / Accepted: 15 September 2004 Published online: 6 November 2004 Springer-Verlag 2004 J. J. Jiao ()) Department of Earth Sciences, The University of Hong Kong, Pokfulam, Hong Kong, China