A geographical information system for marine management and its application to Xiamen Bay, China

Use of GIS (geographical information systems) is an effective and efficient method for gathering and processing large quantities of marine data, such as three-dimensional (3-D) time series of velocity vectors and suspended sediment and pollutant concentrations, and for visual display for result interpretation. A MGIS (marine geographical information system) has been developed for Xiamen Bay and other coastal regions in China. The system can handle object spatial property and a variety of data formats. Besides the standard data manipulation, plotting, and retrieval functions of GIS, two hydrodynamic/mass-transport numerical models for tidal flows, sediment transport, and pollutant dispersion have also been incorporated into the MGIS. Most of the modeling pre- and post-processing operations can be finished within the system. The pre-processing includes mesh generation, gathering of boundary and parallel computation information. The post-processing includes result posting, plotting and analysis. The MGIS has been implemented for more than three years and proven to be a useful integrated tool for generating and revealing various kinds of marine environmental information. Output from the MGIS may provide an important tool for harbor management, and feasibility or environmental impact assessment studies for new coastal structures. The system can be easily adopted in other marine areas through loading new databases and re-verifying the numerical model in the new domain

Drying-wetting approach for 3D finite element sigma coordinate model for estuaries with large tidal flats

An approach to represent drying and wetting processes in a three-dimensional finite element sigma coordinate model is described. This approach makes use of capillaries in dry areas, which can connect to the nearby wet areas. The time marching of the mass conservation equation is modified by introducing a "size factor" coefficient and a water level diffusion term. Therefore, the fictitious water level of the dry nodes can fluctuate with the adjacent wet nodes. This eliminates the artificial pressure gradient appearing in some drying and wetting approaches in the partially wet (transition) elements. This approach results in a null momentum computation at the dry areas, which can guarantee numerical stability and satisfy the mass and momentum conservation. The approach has been applied in a hypothetical case and a real case in Xiamen Estuary, China, with satisfactory results. (C) 2005 Elsevier Ltd. All rights reserved

Effects of green roof on the wind field of a low-rise building

7th International Conference on Fluid Mechanics, ICFM 2015, 24-27 May 2015201812 bcrcVersion of RecordPublishe

Generation of macro-vortices in estuarine compound channels

202307 bcchVersion of RecordRGCPublishe

Strategic planting for watershed restoration in coastal urban environment – toward carbon sequestration by stormwater improvement

202203 bcfcAccepted ManuscriptRGCOthersInnovation and Technology Commission; Research Institute for Sustainable Urban Development (Hong Kong PolyU)Publishe

Integration of a GIS and a complex three-dimensional hydrodynamic, sediment and heavy metal transport numerical model

Hong Kong Research Grants Council [PolyU 5143/04E]; Hong Kong Polytechnic University [G-YD93]The paper presents an integration of a geographic information system (GIS) and a complex three-dimensional hydrodynamic sediment and heavy metal transport numerical model. The integration overcomes the two-dimensional constraint of conventional GIS by supplementing advance tools for three-dimensional, dynamic visualization. The application of a GIS-based interface module together with the three-dimensional, dynamic display tools enhances communication of relationships and trends of hydrodynamic and pollutant transport simulation in both spatial and temporal context, and thus promotes better coastal water quality planning and management. Model functionality includes input data viewing and editing, mesh grid configuration, and result interpretation. The functionality of the GIS-model integrated system is illustrated through a case study on the Pearl River Estuary (PRE). (C) 2008 Elsevier Ltd. All rights reserved

Integration of multi-source data for water quality classification in the Pearl River estuary and its adjacent coastal waters of Hong Kong

The spatial patterns of water quality were studied by integrating a Landsat TM image, 58 in situ water quality datasets and 30 samples from two concentration maps of water quality parameters derived from SeaWiFS and NOAA/ AVHRR images in the Pearl River estuary and the adjacent coastal waters of Hong Kong. The reflectance of TM bands 1-4 was derived by using the COST method. The normalized difference water index (NDWI) was extracted from the raw image and the threshold segmentation was used to retrieve the water pixels of spectral reflectance. In order to study the spectral reflectance categories related to water quality, a dataset comprising 88 sampling points from four spectral bands of a Landsat TM image was used. The samples were positioned according to the availability of water quality parameters in the study area, and five reflectance classes could be finally distinguished by using the cluster analysis. Three supervised classifiers, maximum likelihood (MLH), neural network (NN) and support vector machine (SVM), were employed to recognize the spatial patterns of ocean color. All the 88 samples were divided into two data sets: 65 in the training data set and 23 in the testing data set. The classification results using the three methods showed similar spatial patterns of spectral reflectance, although the classification accuracies were different. In order to verify our assumption that the spatial patterns of water quality in the coastal waters could be indirectly detected by ocean color classification using the Landsat TM image, five optically active water quality parameters: turbidity (TURB), suspended sediments (SS), total volatile solid (TVS), chlorophyll-a (Chl-a) and phaeo-pigment (PHAE), were selected to implement the analysis of variance (ANOVA). The analysis showed that a statistically significant difference in water quality clearly existed among the five classes of spectral reflectance. It was concluded that the five classes classified by reflectance showed distinct water quality characteristics. Therefore, the ocean color classification based on landsat TM images and regular measurements of water quality may provide a reasonable spatial distribution for the coastal water quality. This may serve as an effective tool for the rapid detection of changes in coastal water quality and subsequent management. (C) 2004 Elsevier Ltd. All rights reserved

Assessment of total suspended sediment distribution under varying tidal conditions in Deep Bay : initial results from HJ-1A/1B satellite CCD images

2014-2015 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe