Data analysis for environmental impact of dredging.

The aim of this paper is twofold; first is to identify the environmental impact of dredging related to water and sediment quality; and second is to identify the main factors determining the environmental impact of dredging. The method of this research is data analysis using historical dredging data from three dredging projects performed from 2006 to 2008 at two connected rivers in Perak, Malaysia. The indices measured to identify the impact include: total suspended solids, dissolved oxygen, chemical oxygen demand, biochemical oxygen demand, pH, total organic content, iron, zinc, manganese, copper, chromium, mercury, arsenic, and lead. The factors are then identified through determination of relationships between concentration levels in sediment and water and identification of patterns of impact in the water and caged fish during dredging activities. The results of the analysis show that dredging performed in these rivers has an impact on the environment. The impact includes an increase in levels of most of the monitored indices, including dissolved oxygen and metal concentrations in highly contaminated areas. The main factors associated with the environmental impacts of dredging are the contamination level of the sediment and the contamination level of the neighbouring area, aspects that are the main scientific value added by this paper. This paper draws conclusions regarding the importance of two analyses prior to commencement of dredging: sediment quality analysis and analysis of contamination level in the neighbouring area prior to dredging. The results of this paper could help to better anticipate the environmental impact of dredging and allow for suitable mitigation measures to be identified, especially for developing countries such as Malaysia