Investigating sediment transport in the USA’s aquatic environments

The beginning of a research journey

When I was undertaking an MSc in Applied Marine Science at the University of Plymouth, I was introduced to Professor Keith Dyer (the Course Director) and the wonderful world of cohesive sediment dynamics.

CSOMIO oil floc experiments being conducted at University of Delaware coastal research laboratory

What is flocculation and why is it important?

Clay mineral particles, biological matter and natural biofilm coatings (from marine microorganisms) comprise the fabric of natural muddy sediments and make them sticky.

When these sediments are resuspended in a marine environment and mixed in a turbulent flow, the individual particles stick together and form aggregates (flocs) that are larger in size, settle quicker dynamically, but are overall less dense - due to the trapping of pore water in their structural fabric. This is the process of flocculation.

Flocculation has a large impact on how sediments behave when resuspended and transported within a marine environment, and on the resultant sediment dynamics within a particular location.


Clay minerals have the ability to adsorb pollutants and contaminants to their surface, and the pore water trapped within a floc also can contain pollutants and nutrients. The latter can lead to problems with an excessive growth of algae (eutrophication), such as the negative effects of cyanobacterial algae contamination, arising from climate warming.

This growth of harmful algae has potential human health impacts as, for many Americans, lakes and reservoirs are drinking water sources. It is important to understand how flocs work as they have the ability to mobilise and transport these contaminants within a marine environment.

I'm currently part of a consortium (CSOMIO) which looks at how the 2010 Deepwater Horizon oil spill affected the ecology of the Gulf of Mexico, filling critical gaps in our ability to numerically model the transport and fate of oil in coastal waters.

Measuring water column turbidity in Lake Apopka, Florida

From the UK to the USA

Dr Manning developed the LabSFLOC suite of high-resolution underwater video camera systems; for the past 20 years these have been regarded internationally as a benchmark device for sedimentary particle and floc population dynamical sampling.

I met Professor Ashish Mehta (University of Florida) and Professor David Schoellhamer (US Geological Survey) at international conferences and in 2006 they both invited me to bring LabSFLOC to the USA to look at flocs in Lake Apopka in Florida and in San Francisco Bay.

This went really well and led to me participating in regular surveys in those locations, plus all around the USA including the Northern Californian River Delta, Upper Klamath Lake in Oregon, and Georgia marshes.

Before embarking on the research cruise at Lake Tahoe, I saw a bear walk past me when I was getting a coffee at a Starbucks at Incline Village, Nevada. That doesn’t (often) happen in Plymouth!

Lifesaving while researching

Andrew was returning by boat in rough water from a survey in the southernmost part of San Francisco Bay on the evening of 17 April 2014, when he and three colleagues (Kurt Weidich, David Schoellhamer and William Chan) saw a sailboat entangled in one of the Port of Redwood City channel markers. When a nearby vessel signalled and requested assistance, the survey team stepped in and transported five injured people to shore.

For his decisive and immediate action in the rescue operation, Dr Manning was granted the Exemplary Act Award of the Department of the Interior. Usually only granted to US Federal employees, it is very rare for a UK citizen to be granted such an award, Andrew was the only UK citizen to receive such an award during 2015.

Being awarded the EAA by Prof. David Schoellhamer on the shores of South San Francisco Bay, California

Kaolin clay oil flocs

Communicating the science of cohesive sediments

In December, as I have for the past four years, I will be convening two sessions on cohesive sediment dynamics at the American Geophysical Union (AGU) Fall Meeting in San Francisco – which is the world's largest geophysical & space exploration conference, with typically 25,000-27,000 scientists attending.

In my role as a lecturer at the University of Plymouth, my research forms an important part of my teaching and outreach activities as it provides excellent case studies and alternative approaches to sedimentary science. I include numerous aspects of my North American research in the Marine Sciences, Coastal Surveying and Acoustic and Oceanographic Surveying modules that I lead.