Application of physical habitat simulation (phabsim) modelling to modified urban river channels

Prediction of changes to in-stream ecology are highly desirable if decisions on river management, such as those relating to water abstractions, effluent discharges or modifications to the river channel, are to be justified, to stakeholders. The physical habitat simulation (PHABSIM) system is a well-established hydro-ecological model that provides a suite of tools for the numerical modelling of hydraulic habitat suitability for fish and invertebrate species. In the UK, the most high-profile PHABSIM studies have focused on rural, groundwater-dominated rivers and have related to low, flow issues. Conversely, there have been few studies of urban rivers. This paper focuses on the application of PHABSIM to urban rivers and demonstrates how sensitivity analyses can be used to assess uncertainty in PHABSIM applications. Results show that physical habitat predictions are sensitive to changes in habitat suitability indices, hydraulic model calibration and the temporal resolution of flow time-series. Results show that there is greater suitable physical habitat over a wider range of flows in a less engineered river channel when compared to a more engineered channel. The work emphasizes the need for accurate information relating to the response of fish and other organisms to high velocities. Copyright (C) 2004 John Wiley Sons, Ltd.