For restoration of natural habitats in fluvial ecosystems secondary channels have been proposed. However, the other functions of the river should not be affected too much. In this paper the possibilities and limitations of re-opening these secondary channels are assessed. A methodology is outlined for the design of secondary channels and for the assessment of their effects on the other functions of the river. From the results of several complementary research projects we conclude that secondary channels in the flood plains can be designed to be quasi-stable. When applied only locally, additional measures in the main river are necessary to avoid deterioration of shipping conditions during low flows.