DREDGING IN PORTUGUESE PORTS: A CHANGING PARADIGM
27-28 October 2016, Lisbon, Portugal
Luís Ivens Portela, LNEC, Portugal
Commercial ports play a significant role in Portuguese trade, having handled 80 million tonnes of freight in 2014 and accounting for 57% of exports by weight. In order to maintain and improve operating conditions, ports regularly require maintenance and capital dredging. The volume of material dredged from Portuguese ports (including fishing ports) has been estimated at about 5 million m3 year-1. At the turn of the 21st century, the main options for the disposal of dredged material were marine and estuarine disposal (primarily fine sediments; 45%) and commercial use (sand; 46%), with smaller percentages of other options such as port development (4%) and coastal nourishment (4%). However, practices in the management of dredged material have been evolving since then.
Over the past 30 years, environmental regulations have had a major impact on dredging. Milestones include the introduction of legislation on environmental impact assessment (1990) and dredged material assessment and disposal based on contamination (1995). Although subject to criticism, these regulations have improved access to information and encouraged port authorities to address existing problems. To comply with the new regulations, ports have developed multiannual dredging plans, sediment characterization programmes and, in some cases, water and ecological monitoring programmes. The new regulations were particularly effective at raising awareness about fine sediment contamination and the need to eliminate active sources of contamination.
Coastal protection is a more recent challenge. Dredging requirements often result from the infilling of navigation channels by longshore transport. For a long time, Leixões was the only port to consistently relocate sandy dredged material within the nearshore zone, but since 2006 there is a push to make the practice more widespread. At the Port of Aveiro, coastal nourishments have amounted to 4 million m3 in 2009-2015, following an EIA process, and an additional 2 million m3 are expected in 2017 under a protocol with the Environment Agency. At the Port of Lisbon, nourishments amounted to 3.5 million m3 in 2007-2014. It is believed that the relocation of sandy dredged material within the coastal system may have a significant effect in attenuating erosion in the most critical areas.
Clearly much has been achieved so far, as ports increasingly recognize their responsibility towards the environment. But much work still lies ahead. To make dredging and dredged material management more environmentally sustainable, it must also be as cost-effective as possible. More advanced and efficient strategies and technologies are needed, along with a greater focus of environmental measures and requirements on those aspects that maximize benefits and minimize costs to society.
Last update: 3 October 2016