Jeremy G. Venditti: Research Interests

Research Interests

My primary interests are in the geomorphic and sedimentary processes that shape Earth's surface. I work at a range of temporal and spatial scales from detailed examinations of sediment dynamics occurring over fractions of a second in laboratory channels to monitoring annual river and watershed responses to human impacts. The theme of my research throughout my career has been erosion and sedimentation processes, particularly in river channels. I use a spectrum of research approaches, including field observation and experimentation, physical modeling in laboratories, development of theoretical models, and numerical simulation. I have recently been engaged in research on the topics listed below.

Sediment Delivery to Fraser River Delta: Modeling Framework and Mechanisms

This initiative is designed to advance our knowledge of the mechanics of sand-bedded river channels and, in particular, to develop physically-based predictive tools for how sediments move between their source and ultimate sink in the ocean. The program is designed to use the sand-bedded reach of the lower Fraser River as a natural laboratory to investigate and quantify processes. The Fraser also serves as a prototype for more detailed observations in SFU's new River Dynamics Laboratory that will ultimately lead to a physically-based predictive model for the morphodynamics of sand-bedded river channels, and the Fraser River in particular. At present, there is some understanding of how much sediment is moving into the sand-bedded reach of the Fraser River and how much is being deposited on the Fraser's delta and tidal flats, yet the mechanisms responsible for moving sediment through the 85 km river reach that passes through British Columbia's Lower Mainland is understood only conceptually. The dynamics of sediment in the river control response to flood flows and the quality of habitat in the channel, delta, and tidal flat environments. A physically-based model for sediment routing is required to make reliable predictions of how the sand-bedded channel and the delta environments will respond to various perturbations (i.e. a warmer climate, changes in water flux, changes in sediment flux associated with land use practices, and contemporary variation in sea level). There is a pressing need to make predictions of sediment transport in sand-bedded rivers that empty into the sea, such as the lower Fraser River, because they are often sites of intense urban development world-wide and the dynamics of these natural landscape processes significantly affect the socio-economic viability of this development.

Sand-bedded portion of the Fraser River. The river is confined in a bedrock canyon upstream of Hope, BC (top right). Between Hope and Mission BC, the Fraser deposits its gravel load. At Mission, the river begins to shoal, depositing its sand load, and becomes sand-bedded. (map source http://www.geog.ubc.ca/fraserriver/index.html)

Dynamics of Bedforms in Sand-bedded Rivers

The lower reaches of most large rivers are sand-bedded as they approach the sea and, not coincidentally, many of the world's largest cities have been built along these wide alluvial channels. Thus understanding the physical processes in these types or rivers is critical to our ability to manage these often heavily urbanized fluvial geomorphic landscapes. My work to date has focused on the following topics:

1) Comparisons between turbulent flow fields measured in laboratory and field situations [Venditti and Bauer, 2005]

2) Bedform hierarchy [Venditti et al., 2005; Church and Venditti, 2005 AGU Abst]

3) The transition between 2D and 3D bedforms [Venditti et al., 2005]

4) Bedform growth from initially flat-bed boundaries [Venditti et al., 2005; Venditti et al., 2006]

5) Bedform migration and sediment transport [Venditti et al., 2005; Lin and Venditti, 2009 AGU Abst; Nittrouer et al., 2009 AGU Abst]

6) Bedform dynamics in tidally influences rivers [Allison et al., 2008 AGU Abst]

Collaborators: Michael Church (UBC), Sean Bennett (SUNY Buffalo), Mead Allison (University of Texas Austin), Ray Kostaschuk (University of Guelph and SFU), Martin Lin (Graduate Student, SFU), Megan Hendershot (Graduate Student, SFU), Ryan Bradley (Graduate Student, SFU)

Planview, 10 second time-lapse imagery of bedform initiation and development


i. Bedform initiation from a flat sand bed (click to play)	ii. Bedform initiation from a flat sand bed with a divot (click to play)	iii. Transition between 2D and 3D bedforms (click to play)

Turbulence and Coherent Flow Structures in Rivers

The interaction between flow structure, mobile sediment and bed surface morphology is of central importance in understanding river dynamics. Coherent flow structures drive sediment transport processes in rivers and are capable of sculpting morphological features of rivers at larger scales. I am interested in understanding the dynamics, kinematics and of topology of the coherent flow structures that that are responsible for grain-scale motion, larger scale structures that control bedform dynamics and the channel scale flow structure that governs the morphology of alluvial rivers. To date, much of my work has focused on:

1) The linkage between turbulent flow and suspended sediment transport over dunes [Venditti and Bennett, 2000]

2) Turbulent flow and flow resistance over gravel beds [Venditti et al., 2004 AGU Abst]

3) Turbulent flow over 2D and 3D bedforms [Venditti, 2007]

4) Identification of coherent flow structures in open channels [Keylock and Venditti, 2009]

Collaborators: Sean Bennett (SUNY Buffalo), Chris Keylock (University of Leeds),

Sediment Dynamics Through Gravel-sand Transitions

The beds of alluvial river channels become finer grained moving downstream and often exhibit an abrupt transition from gravel to sand-bedded conditions. Most previous work documenting this phenomenon has focused on small upland streams where sediment supply to the channel is strongly connected to sediment delivery from hillslopes. Fewer studies have focused on the gravel-sand transition in large alluvial channels and none have documented the spatial variability through reaches where transitions occur. The downstream fining pattern observed in the Fraser River is widely cited as a classic example of an abrupt gravel-sand transition in a large alluvial channel.

This initiative is designed to improve our understanding of the morphology and dynamics of gravel-sand transitions in a large alluvial channels. We recently completed a topographic and bed material sampling campaigns [ Venditti et al., 2008] and an examination of sandy bedforms morphology through the transition reach [ Venditti et al., 2009 AGU Abst; Venditti et al., 2010 AGU Abst; Nittrouer et al., 2009 AGU Abst].

Gravel-sand transition in the Fraser River near Mission, British Columbia. The image shows the results of a bed materail smapling programming undertaken in 2007 and 2008 and bed topography measured in 2008. Click on image for a higer resolution version.

Collaborators: Michael Church (UBC), Mead Allison (University of Texas Austin), Ray Kostaschuk (University of Guelph and SFU), Natalia Domarad (Graduate Student, SFU), Maureen Attard (Graduate Student, SFU)

Scientifically-Based Stream Restoration Techniques

Much of the stream restoration conducted in North America is done without considering the physical sedimentary processes that are responsible for channel stability and change. Also, many restoration projects are conducted on short river reaches without considering how a particular reach fits into the larger scale functioning of a river system or landscape. Failure to consider the 'physics' of riverine habitat and broader landscape context of a restored reach often leads to failed restoration projects. I have been working with a number of research groups to provide the stream management/restoration community with methods, techniques, and tools that consider renaturalization of river system processes using state-of-the-art understanding of sediment transport processes. The focus has been to design gravel augmentation techniques that reactivate immobile gravel bed surfaces formed downstream of dams by the addition of sediment pulses.

30m flume at UC Berkeley

From 2004-2006, we undertook experimentation in the 30m flume at UC Berkeley's Richmond field station and at the National Center for Earth Surface Dynamics deigned to provide answers to the following questions:

1) Can coarse surface layers in gravel-bedded rivers be mobilized by finer gravel bedload? [Venditti et al., 2010a, Venditti et al., 2010b]

2) How does surface texture heterogeneity (patchiness) and bed topography respond to dam closure? [Dietrich et al., 2006, Nelson et al., 2009, Venditti et al., 2006 AGU Abst., Nelson et al., 2008 AGU Abst.]

3) Can interlocked grains reduce the mobility of gravel bed rivers? [Wydzga et al., 2005 AGU Abst.]

4) How are sediment pulses propagated through armored channels downstream of dams? [Sklar et al., 2009. Cui et al., 2008, Wooster et al., 2006 AGU Abst, Humphries et al., 2008 AGU Abst.]

5) What are the mechanisms by which sand infiltrates gravel beds? [Leonardson et al., 2006 AGU Abst.]

6) Can mobilization of the coarse surface layer release fine sediment trapped beneath the surface? [Wydzga et al., 2006 AGU Abst.]

Collaborators: Bill Dietrich, Peter Nelson, and Toby Minear (UC Berkeley), Leonard Sklar, Jessica Fadde, and Robert Humphries (San Francisco State U.), Aleksandra Wydgza (UC Santa Barbara), Yantao Cui (Stillwater Sciences) and John Wooster (NOAA)

Movies of fine sediment pulses moving through the 30m flume at UC Berkeley's Richmond Field Station during experiments on gravel mobilization by gravel pulses


i) Pre-augmentation conditions with low sediment transport (click to download)	ii) Fine augmentation pulse passing downstream (click to download)	iii) Mobilized coarse particles moving over fines (click to download)

Flow and Sediment Transport Dynamics in Gravel-Bedded Streams

Quill Creek, Yukon Territory

Gravel-bedded streams dominate the mountainous environs of western North America and understanding process and mechanisms in these streams are critical to developing appropriate management strategies in these areas that are undergoing urban or industrial development. In collaboration with a number of talented researchers, I have been exploring a range of fundamental topics including:

1) Linkages between sediment supply, development and dynamics of bed surface patchiness and channel topography [Dietrich et al., 2006, Dietrich et al., 2006, Venditti et al., 2006 AGU Abst, Nelson et al., 2009, Nelson et al., 2008 AGU Abst. Luzi et al., 2010 AGU Abst., ]

2) Structural features (particle interlocking, imbrication, clusters and cells) of gravel-bed surfaces [Venditti et al., 2004 AGU Abst, Wydzga et al., 2005 AGU Abst, Hendershot and Venditti, 2010 AGU Abst]

3) Sediment entrainment in steep streams [Lamb et al., 2008]

4) Fine sediment infiltration, embeddedness, and flushing [Leonardson et al., 2006 AGU Abst, Wydzga et al., 2006 AGU Abst.]

Collaborators: Bill Dietrich, Peter Nelson, and Toby Minear (UC Berkeley), Leonard Sklar (San Francisco State University), Mike Lamb (Caltech), Aleksandra Wydgza (UC Santa Barbara), David Luzi (Graduate Student, UBC), Megan Hendershot (Graduate Student, SFU)

Environmental Fluid and Sediment Dynamics Laboratory

River Dynamics Research Group

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