Research Highlight: Nilay Iscen
Nilay is a first year PhD student working in the area of environmental hydraulics and sediment transport. She received her BS and MS degrees from Middle East Technical University in Turkey and is currently working on an experimental study examining the morphodynamic and hydraulic co-evolution of cohesive alluvial fans.
Current Research Summary: Alluvial fans form when a sediment-laden flow meets a significant decrease in slope or loses its lateral confinement. They are unique sedimentary environments based on their morphology, and both hydraulic and sedimentologic processes. Alluvial fans are formed by autogenic cycles of channelization, terminal deposit formation, channel back-filling and channel abandonment, and they create dynamic landscapes sensitive to change (at coastlines) and increase hazard potential to infrastructure and human life in mountainous environments. In order to better understand and quantify the sensitivity of these landscapes to a changing climate, and the risk of channel abandonment or migration, the physics of the autogenic cycles must be understood. The purposes of this study are, first, to create a cohesive alluvial fan with persistent channels and subcritical flow, and to identify the mechanism that leads to avulsion and develop predictive relations for channel switching. Experiments are conducted in a laboratory tank with controlled sediment and water supply feeding the fan. The evolution of the spatiotemporal fan topography is recorded using overhead images and a laser scanning system. Quantitative measurements of the flow velocity in the self-formed channels and the flow depth also permit the analysis of fan hydraulics. For the future studies, it is expected that the observations and experimental results of this study on cohesive alluvial fans will contribute to the understanding of the hydraulics and the morhphodynamics associated with the subcritical deep water fans. See the following link for a time-lapse movie showing channel extension, filling, and avulsion (movie).