NSF-BSF: Collaborative research: The Processes and feedbacks that induce multi-scale interactions between local divide migration, drainage reversal and escarpment evolution

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The structure of river networks impacts the spatial distribution of elevation, water, and life across Earth’s surface. Interestingly, this structure changes through time by movement of the water divides that separate river basins. The divide migration process occurs at the local hillslope scale but the driving forces for it are rooted in large scale tectonic and climatic changes. Furthermore, local processes of divide migration influence the broader geomorphic, hydrologic, and ecologic functionality of the Earth’s surface. The proposed research explores the mechanisms through which these multi-scale processes occur. More specifically, how local topographic, hydrologic, and lithologic conditions lead to a cascade of feedbacks that can ultimately have a large scale impact on the Earth system. This binational project compares and contrasts arid and humid research sites in Israel and the USA, respectively, and will thus strengthen research collaboration between the two countries. The research team will also develop and lead an enhanced science education program for K6-8 students in schools in Pennsylvania and Colorado, including schools with high attendance of underrepresented populations.Water divides play a critical role in controlling the form of landscapes and shaping hydrologic and geomorphic functionality. The mobility of water divides is inherently related to the local hillslope and fluvial processes that control the adjacent relief. At the same time, divide mobility leads to reorganization of the drainage network, which significantly influence large-scale topographic, isostatic, and stratigraphic patterns. At present, the processes and feedbacks by which local hillslope and fluvial regimes interact with basin-scale drainage reorganization and with large scale topographic and isostatic changes remain generally unexplored. To address these knowledge gaps, this research focuses on the juxtaposition of topographic escarpments and reversed channels (an end-member of reorganization), where the initial conditions for divide migration are relatively well constrained. In this setting, the topology and sediments of the reversed channels record the history of divide migration. These channels preserve evidence for how local lithologic and hydrologic conditions act as a tipping point that drives the system into a cascading response that results in drainage reorganization, topographic changes and potentially isostatic adjustments. To explore the generality of these processes, the investigators will compare and contrast the emerging landscape dynamics in both arid and humid field sites in Israel and the USA, respectively, across different lithologic and tectonic settings. They will use field mapping and topographic analyses, in conjunction with landscape evolution models and geochronological analyses to constrain the controlling parameters and the rates associated with different processes of divide migration, flow reversals, and the evolution of escarpments.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.