The extraction of kinetic energy from tidal flows is an interest of the renewable energy industry with large scale assessments of the potential resource already conducted. These assessments however use the, natural kinetic energy flux as the primarily metric of the available resource. This approach has significant limitations when it is applied to tidal channels, particularly those tidal channels that branch into multiple sub-channels. Small amounts of energy extraction may not cause significant changes in the total flow through a channel, however the relative flows through the sub-channels can be drastically affected. It is this diversion of the flow that becomes the primary control on the extractable energy. As such the, relative resistance of the channels plays an important role. (C) 2009 Elsevier Ltd. All rights reserved.