| Abstract: | Data from large-scale debris-flow experiments are combined with modeling of particle-size segregation to explain the formation of lateral levees enriched in coarse grains. The experimental flows consisted of 10 m3 of water-saturated sand and gravel, which traveled ~80 m down a steeply inclined flume before forming an elongated leveed deposit 10 m long on a nearly horizontal runout surface. We measured the surface velocity field and observed the sequence of deposition by seeding tracers onto the flow surface and tracking them in video footage. Levees formed by progressive downslope accretion approximately 3.5 m behind the flow front, which advanced steadily at ~2 m s-1 during most of the runout. Segregation was measured by placing ~600 coarse tracer pebbles on the bed, which, when entrained into the flow, segregated upwards at ~6–7.5 cm s-1. When excavated from the deposit these were distributed in a horseshoe-shaped pattern that became increasingly elevated closer to the deposit termination. Although there was clear evidence for inverse grading during the flow, transect sampling revealed that the resulting leveed deposit was strongly graded laterally, with only weak vertical grading. We construct an empirical, three-dimensional velocity field resembling the experimental observations, and use this with a particle-size segregation model to predict the segregation and transport of material through the flow. We infer that coarse material segregates to the flow surface and is transported to the flow front by shear. Within the flow head, coarse material is overridden, then recirculates in spiral trajectories due to size-segregation, before being advected to the flow edges and deposited to form coarse-particle-enriched levees. |
| Genre: | Article |
| ProdID: | 70037877 |
| Citation Author: | Johnson, C. G.; Kokelaar, B. P.; Iverson, R. M.; Logan, M. ; LaHusen, R. G.; Gray, J. M. N. T. |
| Citation Contributing Office: | Volcano Science Center |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | |
| Citation Issue: | F01032 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Journal of Geophysical Research F: Earth Surface |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | 23 p. |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | American Geophysical Union |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Grain-size segregation and levee formation in geophysical mass flows; 2012; Article; Journal; Journal of Geophysical Research F: Earth Surface; Johnson, C. G.; Kokelaar, B. P.; Iverson, R. M.; Logan, M. ; LaHusen, R. G.; Gray, J. M. N. T. |
| Citation Start Page: | |
| Citation Volume: | 117 |
| Citation Year: | 2012 |
| Type: | citation/reference |
| Text: | Grain-size segregation and levee formation in geophysical mass flows; 2012; Article; Journal; Journal of Geophysical Research F: Earth Surface; Johnson, C. G.; Kokelaar, B. P.; Iverson, R. M.; Logan, M. ; LaHusen, R. G.; Gray, J. M. N. T. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1029/2011JF002185 |
| Date Other: | Mon, 26 Mar 2012 00:00 -0500 |
| Publisher: | American Geophysical Union |
