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