Quantitatively evaluating restoration scenarios for rivers with recreational flow releases
Rivers worldwide have been drastically altered in terms of hydrology and morphology. To date, restoration has focused heavily on channel design (i.e., channel morphology), despite the well-known importance of flow regime on controlling ecological processes. In addition, there are few quantitative tools with which to directly and quantitatively compare alternative restoration scenarios. Here we leverage the ecological dominant discharge approach to develop a simple method for quantitatively comparing the effect of different restoration strategies on an ecological metric, in-stream hydraulic habitat (i.e., limiting depths and velocities of flow for fish). We apply this approach to the case of a river ecosystem impacted by recreational flow releases. The analysis shows that enhancing channel morphology will result in limited ecological gains and that greater habitat could be gained through changes in the hydrologic regime. Greater quantitative tools are needed for directly comparing the potential ecological gains of different restoration approaches, and these tools should be usable during the initial evaluation stages of a restoration project; our approach provides a starting point in this direction. Copyright © 2011 by the American Geophysical Union.
