Pierre Julien on Bed Forms, High Concentration Flow, and Engineering Rules of Thumb

RSM River Mechanics Podcast

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