Downstream morphological change in response to dam construction: a GIS based approach for the Lower Ord River, Western Australia

Flow regulation in the Lower Ord River began in 1963 with the completion of the Kununurra Diversion Dam, part of a large-scale irrigation scheme in the far north of Western Australia. What was previously an ephemeral river punctuated by large flood events now contains permanent, regulated flows all year round, and fundamental changes in the downstream channel morphology are now evident. Further changes to the regulated flow regime are planned as part of the eventual expansion of the irrigation area. It is necessary to understand and document the channel responses that have occurred in the Lower Ord so far as a result of flow regulation. This paper presents a GIS based investigation into morphological change in the Lower Ord River. Geomorphic surface data are largely generated from sequential aerial photographs, calibrated using field observations and historical records. Results illustrate the changes in the total area of each surface type, the direction of change in bar evolution and the significance of changes in channel width throughout the study reach.