Over his career Dr. Bill Dietrich has had an outsized influence on both the discipline of geomorphology and the community that surrounds the discipline. He is Professor Emeritus in the Department of Earth and Planetary Science at the University of California, Berkeley. Dr. Dietrich is one of the most influential geomorphologists of the last several decades, known for developing process-based theories of landscape evolution and geomorphic transport laws for soil production, hillslope transport, and river incision. His work spans hillslopes, rivers, debris flows, sediment transport, and the coupling of ecological and geomorphic processes. Over his career he has helped establish many of the conceptual and quantitative frameworks that modern geomorphology relies on today, and his publications are close to 70,000 citations (which is a truely astounding number). He was elected to the U.S. National Academy of Sciences in 2003 and has received several of the field’s highest honors, including the Robert E. Horton Medal of the American Geophysical Union for outstanding contributions to hydrology and the G.K. Gilbert Award for major advances in Earth-surface processes, which is apt because I see his work embodying Gilbert's tradition. Bill also began "the Gilbert Club" an AGU adjacent gathering that has become a center of mas for the geomorphic community, which we talk about in the episode.

As I try to grow in my ability to predict river behavior and manage our interactions with our nation's waterways, I find I'm learning - approximately in equal parts - from the worlds of engineering and geomorphology, so I am trying to deliver heuristics and insights from those overlapping - but separate - thought worlds. In this episode we go deep into the science of upland river processes, including insights that have helped me along the way.

We will have some bonus content on the YouTube channel...but you won't want to miss this: https://youtu.be/fixiMpBB3LE
(an easter egg priview for the people who read episode notes)

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248

So far on this podcast we've generally used the noun "sediment" to describe sand, gravel, and maybe cobbles and boulders. But the same word also gets used for silts, clays, and muds - materials that behave so differently that lumping them together as "sediment" can blur important distinctions. This podcast was overdue for a conversation about fine sediment, and I knew exactly who I wanted to talk to.

In the notebook where I track episode ideas, I labeled this one the “ERDC Cohesive Brain Trust.” I wanted to sit down with the team for the Corps of Engineers that I call when I have questions about "very small sediment", and the team I point engineers toward when they need cohesive measurements or insight for a project or model.

That team is Dr. Dave Perkey, Dr. Jarrell Smith, and Dr. Danielle Tarpley, all based at the USACE Coastal and Hydraulics Laboratory (CHL) at the Engineering Research and Development Center (ERDC) in Vicksburg. A lot of the Corps’ sediment expertise lives there. We’ve had several guests from ERDC over the years, and I’ve spent a lot of my own career collaborating with sediment specialists there. But Dave, Jarrell, and Danielle work on a part of the sediment world that is very different from the sand-and-gravel problems that dominate a lot of my work.

Their focus is sediment that is finer - often much finer - than about 60 to 70 microns, roughly the diameter of a human hair. In the first half of this conversation, they lay out the basic properties and processes of cohesive sediment. Then we move into the research they’ve done to push that science forward. So whether mud is new territory for you or already part of your world, I think there’s a lot here that you will find useful.

Dave Perkey has spent nearly two decades at ERDC studying cohesive sediment properties and processes, especially erosion, transport, and geochemical composition. He also manages the Regional Sediment Management program - the RSM behind the title of this podcast - and it is not much of a stretch to say this season would not exist without him.

Jarrell Smith has been a research engineer at ERDC since 1994, working on sediment transport, hydrodynamics, cohesive and mixed beds, and sediment-vegetation-turbulence interactions. We also talk about one of the tools he’s especially known for, the Particle Imaging Camera System, or PICS, which I recently recommended on one of our own reservoir projects.

Danielle Tarpley is a research oceanographer whose work spans sediment transport and hydrodynamics in inland and coastal settings. She works across field data collection, analysis, and modeling, and brings a great project-grounded perspective to the conversation.

Dave, Jarrell, and Danielle took different paths through the Carolinas for their master’s work, but all earned PhDs through VIMS at William & Mary.

And watch the HEC sediment YouTube channel for some videos illustrating the fine-sediment measurement techniques they describe.

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248

I only know one person who can claim >60 years of federal service. This episode's guest, Mike Spoor. Mike spent those years with the US Army Corps of Engineers Huntington District (in West Virginia on the banks of the Ohio River) and even more years before that as a contractor to the Kansas City District.

But Mike did not just log federal service. He focused curiosity and insight with a relentless field program to convert those years into insight. Mike's decades of stories on the Ohio River and it's tributaries, and the impact of disturbances old (glaciers) and new (coal mining) is exactly the sort of conversations I had in mind when I launched this project. I don't think we got to 10% of Mike's stories, but somehow managed to cover an impressive range of river processes and projects, and some real insight on how he approaches rivers.

I talked to Mike about the history of the Ohio River, the flood of record, and untangling the role of glacial-legacy soils on bank failure processes...and how a careful, causal understanding of these processes helped him identify the most cost-effective approach to mittigate them. We also talked about the impact of coal mining on rivers and reservoirs and the island erosion and restoration work that led to his Golden Eagle award.

It was a fun and informative conversation and I'm thrilled to share it.

(The interlude music in this episode is Dusty Horizons by Score Wizzard and HEC did the editing on this one).

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248

Dr. David Topping is a Research Hydrologist with the US Geological Survey.

He did his undergrad at MIT, a masters and Phd at the University of Washington and has published >100 well cited peer review publications.

Dr Topping has worked with the USGS for >30 years but for the last 18 or so have been with the Grand Canyon Monitoring and Research Center in Flagstaff AZ where he has been one of the reasons that the Glen Canyon releases have become in one of the most ambitious and carefully measured protype sediment experiments in history.

And it is his teams extensive and precise measurements of these experiments and thoughtful analyses of those data that echoed through multiple aspects of my work in the years that followed.

I went back to the papers we talk about in this episode several times…

…when I was working on bed mixing algorithms in HEC-RAS

…and when I was working with the Corps’ Omaha district to restore sand bars on the Missouri river

…and when I was interpreting sediment time series, from the main Amazon tributaries…

I kept finding myself back in his literature.

His team’s work on processes that build and erode sand bars, his distinction between flow regulated and bed regulated transport, and his careful identification of the time scales and grain sizes at play when we think about ‘supply limitation’ and disequilibrium transport have all made their way into my work and my mental model of rivers.

You can find more of his work at these links:

https://www.usgs.gov/staff-profiles/david-j-topping

https://www.usgs.gov/centers/southwest-biological-science-center/science/river-sediment-dynamics

https://www.gcmrc.gov/discharge_qw_sediment/

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248

I grew up in one of North America’s great snow belts…and started my career in Buffalo NY
So, that background and my fascination with sediment transport primes curiosity in ice transport.
I’m sure my ice friends would cringe at this, but I sometimes call ice transport as upside down sediment transport.

But despite the symmetry of ice and sediment transport, they are separate, complicated, disciplines with little overlapping expertise.

Which is why its remarkable, that this episode’s guest is not only is not only world class in both disciplines, but unquestionably the go-to global expert in how they interact.

It is fair to say that just about everything I know about how ice effects sediment transport and river morphology, I learned from Dr. Rob Ettema

So I wanted to have Rob on the podcast to talk about the interactions between ice and the other river processes we tend to talk about in this feed. But recognizing that maybe not everyone who listens to this podcast, is initiated into the wild world of fluvial ice dynamics, we start out with some basics of river ice-formation and transport.

But then we not only dove into the differences between ice-affected and ice-free rivers, but also how ice affects rivers of different latitudes, depths, and even flow directions.

Dr. Rob Ettema retired Colorado State University last year, where he has been a professor since 2015 and continues to work as a research scientist. Before that he taught (and served as Engineering Dean) at the Universities of Iowa and Wyoming.

He has edited ASCE’s cold regions journal, and won that society’s Rouse and Einstein (2015) Awards, which is particularly apt as he has written biographical works on the scientists both of those awards are named after.

He is well know for his work on ice and scour; the former we talked about at length and the latter we barely touched. But Dr. Ettema, is also one of those researchers, that has multiple self-contained, bodies of work, which have each influenced me enough, that I would have invited him on the podcast for either topic.

So in the second half of the conversation, we explore Dr Ettema’s interest in the history of the hydraulic and sediment disciplines, and a genre of literature in which he is second to none: sediment science biography.

We talk about lessons from the characters he has written about, including names like Rouse, Einstein, and Radkivi.

This will wrap up our Colorado State trilogy.
Kind of…we are also releasing some remarkable bonus content with this episode.

Jennifer Bountry (Bureau of Reclamation) invited Dr. Ettema and Dr Julien down to the Bureau’s technical service center to teach a short course together. She provided the zoom footage.

So I edited a little bit and we are releasing the whole short course on the HEC sediment Youtube channel. If you found the last two episodes interesting, we have about 8 hours, of formal technical content for you to dig into.

We’ll link

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248

Dr. Pierre Julien joined the Colorado State faculty almost 40 years ago, where he worked at CSU’s Engineering Research Center and Hydraulics laboratory.

His book, Erosion and Sedimentation, is one of my most common references, and several of the algorithms we have in HEC-RAS (particularly for mud and debris flows) come directly from this text. But while Dr. Julien’s textbook includes as many partial differential equations and tensors as any other hydraulics text – maybe more – it also includes “rules of thumb” scattered throughout.

I have integrated several of these nuggets of actionable, river mechanics wisdom into my field toolbox. They are heuristics I use regularly to quickly triage river processes and engineering proposals while standing next to a river or sitting in a meeting.

So I was curious if these rules of thumb would make an appearance in our conversation…and I was not disappointed. We do talk some theory. He shared a couple great metaphors that helped me visualize some of the complex theoretical principles of fluid mechanics better than I had going into the conversation.

But Dr. Julien does, also, intentionally develop these decision heuristics and rules of thumb, to help practitioners quickly rule in or rule out alternatives and they popped up throughout our conversation.

Dr Julien won the Einstein award in 2004 and the Hunter Rouse award in 2015 the American Society of Civil Engineers lifetime achievement awards for sediment and hydraulics respectively (which is apt as we ended up talking about both the men those awards were named after). He was also named a Distinguished Member of the American Society of Civil Engineers - their highest honor - in 2022.

Dr. Julien has completed projects world-wide with 50 different agencies including world bank and UNESCO and has guided at least 120 masters students and 44 PhDs from 16 different countries.

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248

We’re kicking this season off with one of the most prolific researchers in River Science.

Dr. Ellen Wohl is a Fluvial Geomorphologist at Colorado State’s Warner College of Natural Resources.

As we will discuss, Dr. Wohl has explored and studied rivers on 6 continents (so far). But she has also focused on river processes in the Colorado front range for more than 20 years, Turning up some important insights from both these scales.

I’m not sure if Dr. Wohl leads the fluvial research community in annual words published…But she has to be in the conversation. In addition to countless peer-review papers she is also prolific in short-form and long-form science communication, publishing frequent blog posts and more than a dozen books.

We managed to talk about a pretty wide range of topics, including large river processes, the flood pulse model, the history and current state of restoration research and practice, and a big idea we haven’t interacted with much on this podcast yet: fluvial connectivity.

I first connected with her work through the multi-author review papers she led on the state of river restoration science and practice. These papers came out twenty years apart, and the second one came out twenty years ago, so I was interested to check in on the state of restoration research and what we’ve learned about this no-longer novel field.

But because of her body of work, an interview with Ellen can only touch on a small fraction of her work. Since I was asking the questions, our conversations mainly followed my interests, and some of her most cited work. But this link provides a gateway to a broader range of her work:

https://sites.warnercnr.colostate.edu/ellenwohl/

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248

The peer review process can feel like hazing to a new (or not-so-new) river scientist. Many excellent practitioners are learning from their rivers every day, but it can feel like if it doesn't get into peer review, it doesn't "count."

So we separated this short segment from my conversation with Dr. Amy East, the Editor-in-Chief of AGU's Journal of Geophysical Research: Earth Surface (and >10 years experience editing high impact journals) to provide a little primmer on how to negotiate the peer review process. Amy has some really helpful thoughts on how to move from a "Report on a River" to a "Scientific Contribution" that will land well in a journal.

...and look for the first episode of Season 4 in a few weeks.

This series was funded by the Regional Sediment Management (RSM) program.

Mike Loretto edited the first three seasons and created the theme music.
Tessa Hall is editing most of Season 4.

Stanford Gibson (HEC Sediment Specialist) hosts.

Video shorts and other bonus content are available at the podcast website:
https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/the-rsm-river-mechanics-podcast

...but most of the supplementary videos are available on the HEC Sediment YouTube channel:
https://www.youtube.com/user/stanfordgibson

If you have guest recommendations or feedback you can reach out to me on LinkedIn or ResearchGate or fill out this recommendation and feedback form: https://forms.gle/wWJLVSEYe7S8Cd248