| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | July 10, 2015 |
| Latest Amendment Date: | October 21, 2016 |
| Award Number: | 1452337 |
| Award Instrument: | Fellowship Award |
| Program Manager: |
Luciana Astiz
lastiz@nsf.gov (703)292-4705 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | November 1, 2015 |
| End Date: | October 31, 2017 (Estimated) |
| Total Intended Award Amount: | $87,000.00 |
| Total Awarded Amount to Date: | $174,000.00 |
| Funds Obligated to Date: |
FY 2017 = $87,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
Oakland CA US 94609-1103 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Pasadena CA US 91125-0001 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Postdoctoral Fellowships |
| Primary Program Source: |
01001617DB NSF RESEARCH & RELATED ACTIVIT 01001718DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Dr. Marisa C. Palucis has been granted an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at the California Institute of Technology. The initiation mechanisms and hazards associated with debris flows generated through runoff are poorly understood, but are common in areas recently burned by fire, and in semi-arid to arid regions with sparse vegetation and an abundance of exposed bedrock. Dr. Palucis' investigation will focus on examining two possible mechanisms that may initiate debris flows generated by runoff, progressive transport of the sediment and elevated pore pressures. The results will be used to inform about location (i.e. slopes) and environmental conditions (i.e. grain size and discharge) leading to debris flow initiation, which is needed for hazard mapping and assessment, especially in fire prone regions of the world. The education plan will consist of developing and implementing interactive desktop laboratories will be presented on a monthly basis to K-8 students within the Pasadena Unified School District (PUSD). Also, two undergraduate students will be mentored through Caltech's Summer Undergraduate Research Fellows (SURF) program, where the students will design and perform flume experiments over the course of 10-weeks.
The PI will conduct multiple flume experiments to investigate these two mechanisms, where the flow discharge (and hence shear stresses on the bed), grain size distribution (which may control pore pressure generation in granular flows), and slope are tested independently. These experiments will provide a valuable and robust dataset linking sediment supply characteristics and flow hydraulics on steep slopes. The experimental data collected here will provide one of the most detailed datasets to date on sediment transport modes and will bridge the gap between data being collected in the field and experimental data. Debris flows are a major geomorphic process in mountainous landscapes, though most models currently do not account for debris flows as sediment transport agents. Therefore, better definition of the parameter space describing debris flow occurrence is a key ingredient for predicting landscape evolution over longer timescales.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Sediment transport within mountain rivers controls their morphology, supplies sediment downstream for aquatic habitat, and can be a major hazard to life and infrastructure. Sediment tends to move by dilute river transport where channel slopes are relatively gentle, and by debris flows at very steep gradients; however, the dominant mode of transport is not understood for the range of bed slopes in between. To address this knowledge gap, we performed controlled laboratory experiments in a steep, 12 m long recirculating flume to determine when and where river processes transition to debris flows. Surprisingly, we found that rather than traditional river transport or debris flow initiation, a distinct third mode of transport developed called sheetflow. Sheetflows are concentrated granular slurries that are a hybrid between traditional bedload transport and mass flows. They occur on lower gradient sandy beds under high bed stresses, but have not been previously documented in steep mountain streams. We mapped the parameter space where sheetflows occur, and quantifed controls on their thickness and particle velocity profiles. We also did detailing mapping of bedform geometry under different flow conditions, and quantified how channel slope and bedform geometry affects sediment transport fluxes in steep streams. Overall, our results indicate that there is a continuum of behavior as a channel bed steepens, from fluvial processes to sheetflow to debris flow, which has significant implications for predicting sediment fluxes, flow resistance, and channel bed morphology in mountain streams.
In terms of broader impacts, this work has provided new insight into debris-flow initiation processes, which can better inform the public and policy makers about the dynamics of an ever-changing planet, leading to sustainable solutions for land-use, hazard assessment and environmental restoration. This project also gave two undergraduate students exposure to a broad set of tools in the physical sciences, one of whom is continuing his education in the earth sciences, and it has brought STEM exposure to young learners through desktop labs for K-12 students in the Pasadena (CA) and Hanover (NH) area.
Last Modified: 02/28/2018
Modified by: Marisa C Palucis
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