The aim of the HARBASINS project was to enhance the compatibility of management strategies and international cooperation for the North Sea's coastal waters, estuaries and river basins. The focus has been on harmonisation of the EU Water Framework Directive and the international cooperation on integrated management of estuaries and coastal waters in the North Sea Region, ultimately leading to ecosystem restoration and compatible instruments which ensure sound environmental management of interconnected coastal zones in the North Sea. Achievements: Technical products of the HARBASINS project on hydromorphological models have influenced Water Framework Directive prescribed denomination for some German estuaries changing them from Heavily Modified to Moderately Modified. This has caused an enormous present day and future cost reduction for the German River Basin Water Management.HARBASINS has also developed and refined evaluation tools, such as a Fish-index for estuaries, Environmental Integrative Indicators and the criteria for a harmonized assessment of Heavily Modified Water Bodies in transitional waters using morphodynamic models.The steps towards a harmonised transnational management strategy for coastal and transitional waters have been addressed to policy-makers, managers and scientists, each of whom have had their own concerns and responsibilities within this on-going harmonisation. For instance, the experience gained during the HARBASINS project, especially on estuarine habitat restoration, will be taken up for the further development of the Wadden Sea 2008 - 2010. HARBASINS has underlined that the Ecosystem Approach is the most appropriate way to integrate ecology, economy and society demands for a specific management area, such as estuaries or larger coastal ecosystems like the Wadden Sea. In addition, the project has decided to use the existing Ecosystem Approach in the Scheldt and Humber estuaries as a best practice.