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22-19. Linking sediment flux to hydrological variation and geomorphic change—modeling erosion, channel development, and forecasting long-term evolution of highly perturbed fluvial systems

This opportunity focuses on modeling linkages among sediment flux, hydrologic variability, and complex geomorphic change in volcanically disturbed fluvial systems in order to better quantify relations among sediment erosion, transport, and storage following significant fluvial disturbance and to forecast long-term evolution of perturbed fluvial systems under varying climate scenarios. 

Description of the Research Opportunity

Explosive volcanic eruptions can alter the hydrogeomorphic functioning of landscapes downstream and downwind of volcanoes by damaging vegetation, altering hydrologic runoff, and depositing large volumes of erodible sediment on hillslopes and in valleys (e.g., Pierson and Major, 2014; Major, 2022). As a result, hydrogeomorphic processes are subject to significant disequilibrium, commonly resulting in extraordinary sediment erosion and transport. Following an eruption, channels can incise meters to tens of meters, widen by tens to hundreds of meters, and deliver exceptional amounts of sediment downstream causing channel instability that can persist for years to decades and posing significant societal challenges. Fluvial responses to landscape disturbance are affected by a variety of hydrological flows, and threshold conditions for dynamical channel response may evolve over time in conjunction with post-event ecological evolution. Although years to decades of geomorphic changes and sediment yields are well documented at some volcanoes (e.g., Gran and Montgomery, 2005; Gran et al., 2011; Major et al., 2016, 2018, 2019, 2020, 2021; Ulloa et al., 2016), and studies have shown that magnitudes of flood flows may increase temporarily following eruptions (e.g., Major and Mark, 2006), there has been relatively little work that explicitly and quantitatively links documented sediment fluxes, hydrologic variability, and complex geomorphic evolution of disturbed systems in a manner that allows long-term forecasting of geomorphic evolution and hydrogeomorphic recovery (cf. Meadows, 2014; Zhang et al., 2023). Because abnormal sediment delivery from volcanically disturbed basins can persist for decades and possibly longer, quantitative forecasts of long-term yields tied explicitly to geomorphic evolution channel systems are critical for governmental and other management authorities tasked with mitigating impacts to flood protection measures and other critical infrastructure (e.g., Sclafani et al., 2018). 

We seek a postdoctoral fellow to advance quantitative understanding of the linkages among sediment flux, hydrologic variability, and complex geomorphic change in disturbed fluvial systems. The successful candidate is expected to undertake research that contributes to the following topical areas: quantitatively elucidate relations among sediment erosion, transport, and storage following significant fluvial disturbance and multi-dimensional geomorphic evolution; quantify linkages among hydrological variability and geomorphic evolution of disturbed fluvial systems; develop or enhance existing models to predict geomorphic evolution of disturbed fluvial systems and to forecast how geomorphic evolution and associated sediment flux may evolve under varying climatic scenarios. The successful fellow will have access to a wealth of geomorphic and hydrologic data from Mount St. Helens, including decades of cross-sections surveys, multiple repeat lidar and other DEMs, and long-term sediment-transport and hydrologic records.  DEMs, cross-sections, and hydrogeomorphic data from other disturbed river systems (by other eruptions, dam removals, mining, etc.) may also provide useful resources. 

An overarching goal of this project is to improve understanding of fluvial responses to significant hydrogeomorphic disturbances to improve resiliency of riverside communities by providing them information to better address risk from exposure to natural hazards, particularly long-lasting sediment hazards following significant fluvial disturbances. 

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas. 



Gran, K.B., Montgomery, D.R., 2005, Spatial and temporal patterns in fluvial recovery following volcanic eruptions – channel response to basin-wide sediment loading at Mount Pinatubo, Philippines. Geological Society of America Bulletin, 117, 195–211, 

Gran, K.B., Montgomery, D.R., Halbur, J.C., 2011, Long-term elevated post-eruption sedimentation at Mount Pinatubo, Philippines. Geology, 39, 367–370, 

Major, J.J., 2022, Subaerial volcaniclastic deposits—influences of initiation mechanisms and transport behaviour on characteristics and distributions. In Di Capua, A., De Rosa, R., Kereszturi, G., Le Pera, E., Rosi, M. and Watt, S. F. L. (eds) Volcanic Processes in the Sedimentary Record: When Volcanoes Meet the Environment. Geological Society, London, Special Publications 520, 

Major, J.J., Bertin, D., Pierson, T.C., Amigo, Á., Iroumé, A., Ulloa, H., Castro, J., 2016, Extraordinary sediment delivery and rapid geomorphic response following the 2008–2009 eruption of Chaitén Volcano, Chile. Water Resources Research, 52, 5075–5094, 

Major, J. J., Grant, G. E., Sweeney, K. R., Mosbrucker, A. R., 2020, A multidecade analysis of fluvial geomorphic evolution of the Spirit Lake blockage, Mount St. Helens, Washington. U.S. Geological Survey Scientific Investigations Report 2020-5027 (54 p.). United States Government (US Geological Survey). 

Major, J. J., Mark, L. E., 2006, Peak flow responses to landscape disturbances caused by the cataclysmic 1980 eruption of Mount St. Helens, Washington. Geological Society of America Bulletin, 118, 938–958. 

Major, J. J., Mosbrucker, A. R., Spicer, K. R., 2018, Sediment erosion and delivery from Toutle River basin after the 1980 eruption of Mount St. Helens: A 30-year perspective. In C. Crisafulli, & V. Dale (Eds.), Ecological responses at Mount St. Helens: Revisited 35 years after the 1980 eruption (pp. 19–44). New York, NY: Springer. 

Major, J.J., Spicer, K.R., Mosbrucker, A.R., 2021, Effective hydrological events in an evolving mid-latitude mountain river system following cataclysmic disturbance—a saga of multiple influences. Water Resources Research 57, e2019WR026851. 

Major, J. J., Zheng, S., Mosbrucker, A. R., Spicer, K. R., Christianson, T., Thorne, C. R., 2019, Multidecadal geomorphic evolution of a profoundly disturbed gravel bed river system—A complex, nonlinear response and its impact on sediment delivery. Journal of Geophysical Research: Earth Surface, 124, 1281–1309. 

Meadows, T., 2014, Forecasting long-term sediment yield from the upper North Fork Toutle River, Mount St. Helens, USA. PhD thesis, University of Nottingham 

Pierson, T. C., Major, J. J., 2014, Hydrogeomorphic effects of explosive volcanic eruptions on drainage basins. Annual Review of Earth and Planetary Sciences, 42, 469–507. 

Sclafani, P., Nygaard, C., Thorne, C., 2018, Applying geomorphological principles and engineering science to develop a phased sediment management plan for Mount St. Helens, Washington. Earth Surface Processes and Landforms, 43, 1088–1104. 

Ulloa, H., Iroumé, A., Picco, L., Mohr, C.H., Mazzorana, B., Lenzi, M.A. and Mao, L., 2016, Spatial analysis of the impacts of the Chaitén volcano eruption (Chile) in three fluvial systems. Journal of South American Earth Sciences, 69, 213–225, 

Zhang, S., Wang, H., An, C., 2023, Renewed incision and complex response of the North Fork Toutle River following the eruption of Mount St. Helens in 1980.  Catena 220,


Proposed duty station(s)

Vancouver, Washington 


Areas of PhD

Geology, hydrology, geomorphology, sediment transport, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered). 



Applicants must meet one of the following qualifications:  Research Geologist, Research Hydrologist, Research Geophysicist, Research Engineer, Research Physical Scientist   

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)