30 Nov 2012
Oyster reefs. Copyright: Wageningen UR
Oyster reefs. Copyright: Wageningen UR

Royal HaskoningDHV, the Institute of Marine Sciences and Fisheries (University of Chittagong, Bangladesh), IMARES and LEI, both part of Wageningen UR, presented the first results of the ECOBAS pilot project in Bangladesh; oyster reefs are a good solution for sustainable coastal defence and aquatic food production. These reefs will contribute to improved safety for humans against coast erosion and flooding, and also deliver a sustainable source of aquatic food.

Notwithstanding many billions of euros that have been spent on water management over a very long time span, society is still confronted with major flooding, droughts and water quality problems. The classic approach is struggling with nature by constructing structures such as revetments or groynes. The question that arises is whether solely the use of pure hard-engineering solutions is sustainable. A concept that can be complementary to these hard-engineering solutions is the Building with Nature approach. Building with Nature uses the natural dynamics of the ecosystem to create flexible and sustainable solutions while enhancing nature values.

Building with Nature

The ECOBAS (Eco-engineering in Bangladesh) project is testing the technical, economical and sociological feasibility of the Building with Nature concept on the southeast coast of Bangladesh. In this concept, coastal defence is combined with the sustainable production of oysters. Shells like oysters naturally create three dimensional reefs, which influence the current and with that the erosion and sedimentation of the coastal area. This can diminish the maintenance costs for hard structures and enhance biodiversity. In the Netherlands small and large scale pilots with oyster reefs have been tested in the Oosterschelde and it showed that enhanced sedimentation occurred behind the reef.

On the southeast coast of Bangladesh local minority people collect oysters and other bivalves and gastropods from the intertidal area. Since only a part of the oyster reef can be harvested to ensure its continuity, it is therefore important to consider the way the oyster harvest is managed in order to prevent over-exploitation. Therefore, the local community needs to be aware of spat settlement, oyster growth and survival and the effects of the reef. The project shows that there are still a number of challenges related to the technical design and the management of the reef for the sustainable exploitation and sales of oysters.

The ECOBAS project is financed by the Dutch Partners for Water Programme. Besides contributing to  safety and providing a source of food, oyster reefs can also stimulate mangrove growth by increased accretion and the stabilization of tidal flats. This is interesting because of the additional possibilities that mangroves offer for coast protection and other ecological and economic benefits.

Feasibility study

In the next phase (January 2013 - November 2014) the concept will be up-scaled. For this, structures will be constructed and installed along the coasts of Kutubdia and Maheshkhali Island. The technical, ecological and economic feasibility will be assessed based on the outcomes of the pilot project and presented in a workshop December 2014.