As the Milk River crosses southern Alberta it displays a classic meandering channel pattern. However, shortly after entering Montana a seemingly inexplicable morphological transition occurs. The fluvial style changes instantly to a chaotic braiding pattern characterized by mid-channels bars dividing flow into multiple channels. This sudden change in channel pattern is an anomalous feature on the landscape of northern Montana. The focus of this presentation is to highlight the causative mechanisms for this morphological transition.
Rivers are amongst the most pervasive geomorphic agents on the earth s surface.
They serve as conduits through which the products of erosion are transmitted from source areas to sedimentary sinks. Rivers not only transport the products of erosion but they themselves can erode the landscape. However, the influx of eroded sediment sometimes exceeds the sediment transport capability of a river and new landforms are created through deposition. Rivers attempt to maintain a dynamic equilibrium whereby they transport the water and sediment load provided from upstream sources without undergoing significant morphological alterations. Four main variables act in concert to govern channel morphology.