Controls on ridgeline profile morphology

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

Natural hazards such as landslides, debris flows, and river flooding threaten lives and infrastructure. Geologists and geological engineers work to identify areas prone to natural hazards and predict when hazards will occur, thereby improving public safety. However, this work requires a physics-based understanding of how landscapes erode and evolve. Geologists have spent over a century studying river and hillslope erosion, but, surprisingly, there is a topographic feature present in all landscapes that has seen almost no study to date. These currently undescribed topographic features are ridgelines – the elevation profile along a topographic divide separating two adjacent watersheds. The current lack of understanding of how ridgelines are shaped and eroded limits predictions of the distribution of landscape relief (i.e., how the steepness of landscapes varies), which is key to predict landsliding, debris flow occurrence, river sediment flux and more. This proposal seeks to understand the processes that set ridgeline shape. Accomplishing this will advance basic science by improving our understanding of how landscapes are formed, and can also lead to improvements in predicting natural hazards. Beyond these benefits, the project includes training for future middle school teachers in basic earth science. Understanding earth science can help students contextualize and understand societal threats such as climate change. Many middle school teachers lack earth science training; providing this training to future teachers can improve the quality of geoscience education for future students. Specifically, this project will modify and add to existing theory to describe the shape of ridgelines. The work will test three hypotheses about the controls on ridgeline slope, the presence of local peaks and saddles along ridgelines, and the form of ridgeline ‘snouts’ (the portion where the ridge dives down to meet the river outlet). Each hypothesis will be tested against a combination of field data from natural landscapes and pre-existing laboratory experiments where landscapes are evolved under controlled conditions. The future teacher training portion of the project consists of a 12-week long professional development course. Future teachers (recruited from a training program at the University of Nevada Reno) will earn $900 stipends and will be taught basic geoscience concepts appropriate for middle school teaching and have the opportunity to develop geoscience lesson plans and present these lessons in local middle schools. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.