Realistic Sedimentary Bedform Prediction: Incorporating Physical and Biological Cohesion (COHBED)

Lead Research Organisation: Bangor University
Department Name: Sch of Ocean Sciences

Abstract

The United Kingdom is a coastal nation with the majority of the population living within a few miles of an estuary or the sea. The nature of the coastline depends on the local conditions of geology and water flow. Rocky coastlines are found where the energy of the sea is high, while mud and sand are found where the energy is lower and these sediments can be deposited. These low energy muddy and sandy (depositional) habitats, are very important for the ecology and economy of the UK. They provide food for many species of birds and fish, but also protect the coastline from the erosive forces of the sea. In addition, they act as a "filter", where pollutants from the rivers are captured and eventually degraded. Because of the importance of these systems, their natural behaviour and stability is of increasing concern as sea levels rise and storm events increase in frequency with climate change. The movement of sediment around the coast of Britain has vast economic and ecological consequences, but surprisingly we have very little scientific information that helps us to predict how natural mudflats and beaches will respond to the changing forces of the tides, wind and waves. When water flows over the sea bottom, the energy of the flow shapes the sediment into wavy features called bedforms (such as ripples). These bedforms help control the erosion and transport of sand, mud, nutrients and pollutants. Information allowing us to predict the shape, size and movement of bedforms is essential for environmental management, hydraulic engineering, benthic habitat biology, computer modelling of particle transport, sedimentary geology, and many other scientific disciplines. However, there is an almost complete lack of knowledge concerning bedforms consisting of mixtures of sand and mud. Sandy sediments are known to be "non-cohesive", because the sand particles do not stick together, whereas muds are made up of smaller particles that do stick together and so are called "cohesive" sediments.

This project, COHBED, will take advantage of the latest developments in measurement technologies to produce information about the growth, movement and stability of bedforms that consist of natural mixtures of sands and muds, a natural condition that is very common but has rarely been studied before. In a new departure, this work includes a multidisciplinary team to combine the physics, mathematics, sedimentology, and biology of these systems, since we recognise that the organisms (from bacteria to sea grasses) that inhabit natural systems also change the erosional characteristics and bedform behaviour. This is why COHBED will include laboratory experiments and field surveys. A series of experiments in laboratory flow channels will investigate key factors that control the behaviour and properties of bedforms, such as:
- System energy: effects of flow velocity, bed friction and flow depth
- Bed properties: particle size, proportion of mud and sand, and biological effects
- Time: the speed of bedform growth and rate of change as flow energy changes
- Particle erosion: changes in the bedforms as smaller particles are eroded away

The results of the laboratory studies will be compared with the behaviour of natural systems. Field surveys will be conducted to validate the predictions derived from the laboratory studies, using new techniques that for the first time allow essential simultaneous measurements of flow, sediment and bedform properties. The COHBED project will maintain the UK at the forefront of this research area and will help us to manage our coasts in the face of climate change.

Planned Impact

The main beneficiaries of the timely knowledge on mixed cohesive bedform dynamics arising from COHBED are all users who depend on more accurate models for the transport of particulate and dissolved matter in aquatic environments. There is a unique opportunity to implement the results of COHBED into improved predictive tools for bedform development, equilibrium morphology and migration, as well as for bed roughness parameters and suspended load concentration profiles that are closely related to bedform properties. These models will be directly applicable, while also forming the basis for future regional sediment transport modelling efforts in complex natural environments.

Scientists will benefit as this project will spark collaborative research in the largely unexplored field of biology- and physics-controlled cohesive mixed sediment dynamics and the project outcomes will provide a vehicle for facilitating more reliable palaeo-environmental reconstructions and improving numerical models of sediment transport. A Numerical Modelling Advisory Committee will be an integral part of COHBED. This committee of independent experts will provide guidance how to ensure that the research outcomes of the laboratory and field experiments and, notably data requirements and data formats, are best obtained for future numerical modelling.

Engineers will benefit from the predictive outputs of modified bedform dynamics from cohesive forces in flows and bed surface sediments. These will help guarantee engineering success when extracting sediment or building structures in and on the sea bed (e.g. pipelines, wind turbines, tidal barrages, oil platforms).

Planning authorities and environmental advisers/managers will benefit from improved Environmental Impact Assessments (EIAs) to which the research outputs will contribute significantly, notably because the likely impacts of new sea bed developments need to be fully understood for engineering safety and habitat preservation. We will engage with these end users, and with engineers, through regular Progress Meetings and a Knowledge Exchange Workshop near the end of the project.

The hydrocarbon industry will benefit from improved architectural models of sedimentary facies and from more confidence in reconstructing and predicting the porosity and permeability of clastic sedimentary rocks in cores and outcrops. The results from this project will be disseminated through the industry-funded Turbidite Research Group (TRG), an internationally recognised leader in the study of deep marine clastic sedimentary systems, of which PI Baas is the Associate for Wales, and PI Parsons and Co-I Peakall are integral members.

Through national and international conference visits, a project website, popular science media and events, publications in international peer-reviewed journals, and a novel Travelling Exhibition "Shifting Seas, Shifting Sands" we will not only engage with our primary users, but we will also disseminate our project outcomes and their implications to the wider public.

The Centre for Catchment to Coastal research (CCCR), SEACAMS and the Society for Underwater Technology (SUT) will be used as vehicles to interact with academic partners, representatives of governmental bodies, and industry through regular seminars/workshops and small group discussion meetings. Our strong links with various branches of the offshore engineering industry will serve to refine experimental methodologies and identify optimal dissemination products. New knowledge will be exchanged with petroleum geologists at the bi-annular sponsor meetings of TRG, and potential users (including the members of the Advisory Committee) will be invited to attend regular Progress Meetings and the Knowledge Exchange Workshop .
 
Description Overview



The University of St Andrews are currently investigating the temporal variation in extracellular polymeric substances (EPS) content and sediment behaviour of different sediment types. These studies will complement the large scale flume studies at Bangor and Hull universities and provide information on the dissolution rate and loss of EPS from the sediment bed over time. Preliminary experiments have been carried out to develop improved protocols, including carbohydrate analysis for studies involving small quantities of xanthan gum and new equipment has been constructed for flume and benthic chamber studies.



Laboratory experiments are supported by a seasonal field campaign in the Eden Estuary, Scotland and these will add contextual information to the laboratory studies. The influence of biological and physical factors on sediment stability in various natural sediment types will be investigated by sampling various water column and sediment bed characteristics. One such characteristic is the presence and variation of natural biofilms within and between seasons and sites. The xanthan gum used in laboratory experiments will be used as a proxy for the EPS found in natural sediments.





Key findings



Laboratory studies



Laboratory studies aim to investigate the effects of natural and artificial EPS on bedform behaviour as well as continuing field studies. Findings to date, suggest that the artificial polymer is removed from the forming ripples throughout flume experiments. This also coincides with the level at which the clay is lost from the system, perhaps suggesting that the polymer and clay are more tightly associated, with the sand forming the ripples. The underlying substrate contains all three components of the mixtures; sand, clay and polymer. Water samples will be analysed to gauge whether the polymer is removed through dissolution from the bed.



An investigation into the erosion and transport of carbohydrate in biological and artificial mixes of cohesive sediments was carried out using mesocosms (artificial sediment and xanthum gum) and an 8m linear flume (natural sediment and EPS) by Louise Russell, a masters student.



Results from preliminary trials (flow resulting in no erosion of the surface) did not show any change in carbohydrate content with time. Very low concentrations of carbohydrates were found in the water samples. Following on from the preliminary trials the maximum achievable flow rate of 72 RPM was used and the sediment surface was artificially disturbed at the start of the experiment immediately prior to switching on the mesocosm motors. This artificial disturbance was designed to be representative of any natural disturbance event which causes erosion. The experiment was run for 3 hours with 3 sampling time points; T0 = the start of the run before the motors were turned on; T1 = 1.5 hours after the motors were turned on; and T2 = the end of the run 3 hours after the motors were turned on. All sampling at T0 was done prior to the disturbance event to provide baseline readings against which any changes in carbohydrate content could be measured. Water at all three time points, but sediment samples were taken at T0 and T2.



Total carbohydrate:

No significant differences in sediment total carbohydrate content (µg g-1) were found between the start and end of the experiment.

A statistically significant difference was found in the water samples (K-W p=0.000). It was determined that there was a significant difference between T0 & T1 (p=0.004) and T0 & T2 (p=0.000) but not between T1 & T2 (p>0.017). Although there is no statistically significant difference between T1 & T2 the mean and median total carbohydrate content (µg g-1) continues to increase with time.



Colloidal carbohydrate:

The colloidal carbohydrate content (ug g-1) was analysed from water samples. There were no significant differences found between time points within the control water samples (p>0.05), however a statistically significant difference was found between T0 & T1 for the experimental group (p=0.008). No significant differences were found between T0 & T2 or T1 & T2 (p>0.05)



A flume study was carried out in an 8m Armfield linear tilting flume to test the null hypothesis that EPS is lost from the surface of natural sediment under conditions of flow, and there is a detectable change in EPS concentration with depth. The flume study was run for 6 hours; T0 represents samples taken at the start to provide baseline readings and T1 samples were taken at the end of the 6 hour period. Sediment samples were taken using syringe cores (2cm diameter). The surface 1.5cm of each core was sectioned into 0.1cm segments which were analysed for total carbohydrate content. This produced a depth profile of bulk carbohydrate content within the surface layers of the sediment. Time constraints meant that only the top (surface) 1.0cm of sediment could be analysed. The remaining samples have been stored in a -80oC freezer for later analysis. No significant difference in total carbohydrate content was found between depths in experimental (flume) samples (p>0.05) at either time point



However when the top 1cm core was combined it was found that the total carbohydrate content in T1 was significantly lower than that of T0 (p=0.000) (Figure 3), suggesting that EPS was being lost from the surface layers of the sediment. Due to the scale of the flume set up we were unable to test whether the EPS was buried or lost to the water column.



Fieldwork



Preliminary results from the fieldwork in the Eden suggests that influence of biogenic stabilisation depends on the sediment type, and how the relative influence of biological and physical factors changes throughout the seasons in very different ways at each of these sites.



Soluble EPS (colloidal carbohydrates) correlates significantly with sediment stability measurements (p<0.001). Colloidal carbohydrate content was also significantly different at each site. The muddy site had significantly higher values for all biological measurements. This site also produces significantly higher erosion thresholds than the other two sites.



Results to date suggest that EPS content may significantly correlate with sediment stability across different sediment types. Granulometry for each time point is likely to reveal variation in the sediment types at each site throughout the year and follow any relationships between particle size distribution and biological characteristics. EPS may reduce the erosion from tidal immersion as well as impact on ripple formation and development in mixed sediments.



Current laboratory analysis is being carried out on samples collected from the Dee field campaign. This aspect of the work will determine where EPS is found in the surface sediments of different areas of the bed forms. A depth profile will be created indicating where EPS is concentrated in three different areas of the bedform (lee, crest and stoss). This data will be paired with data collected by the University of Bangor.
 
Description Manning, A.J. (Editor, 2013). Sediment Transport Processes and Their Modelling Applications. InTech (Rijeka, Croatia), ISBN 978-953-51-1039-2. N.B. 13,504 downloads of entire book (January 2014). 13,504 downloads of entire book (January 2014).
 
Description COHWAV
Amount £65,000 (GBP)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 08/2013 
End 05/2015
 
Description COHWAV
Amount £65,000 (GBP)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 08/2013 
End 05/2015
 
Description BAASI system development NOCL - Thorne 
Organisation European Commission
Department Seventh Framework Programme (FP7)
Country European Union (EU) 
Sector Public 
PI Contribution Under HYDRALAB4 NOC Liverpool has worked with French and Spanish partners on the development of the BASSI system to be used in COHBED
Start Year 2013
 
Description BASSI system development NOCL - Thorne 
Organisation European Commission
Department Seventh Framework Programme (FP7)
Country European Union (EU) 
Sector Public 
PI Contribution Under HYDRALAB4 NOC Liverpool has worked with French and Spanish partners on the development of the BASSI system to be used in COHBED
Start Year 2012
 
Description CBESS colaboration - Hope 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution COHBED mentioned to the Coastal Biodiversity and Ecosystem Service Sustainability (CBESS) programme where wider scale measurements of sediment erosion are being made. COHBED asked to cooperate with development prevision of new ?super? flume from salt marsh erosion studies within CBESS.
Start Year 2013
 
Description COHBED collaboration with HR Wallingford 
Organisation HR Wallingford Ltd
Country United Kingdom 
Sector Private 
PI Contribution Dr Andy Manning, as a Principal Scientist in the Coasts & Estuaries Group at HR Wallingford (HRW), has developed his links between COHBED and HR Wallingford. Two HRW colleagues are now able to assist during the May/June COHBED fieldwork in the Dee Estuary. Dr Tom Benson plans to bring his own floc sampler to the Dee and collect data. Dr Jon Taylor is an acoustics specialist in the Dredging Group at HRW. Jon has a wealth of fieldwork experience and will assist with both LabSFLOC and ADCP measurements (as required). Both Dr Benson and Dr Taylor are able to assist Dr Manning with data processing.
Start Year 2013
 
Description Collaboration with Prof. Decho - Hope 
Organisation University of South Carolina
Country United States 
Sector Academic/University 
PI Contribution Professor Alan Decho (University of South Carolina) is studying biofilm dynamics at COHBED sites as part of a MASTS visiting fellowship scheme.
Start Year 2013
 
Description Fife Coast and Countryside Trust Ranger 
Organisation Fife Coast and Countryside Trust
Country United Kingdom 
Sector Charity/Non Profit 
PI Contribution Regular updates are provided to the Fife Coast and Countryside Trust Ranger to maintain open communication and amicable collaboration.
Start Year 2014
 
Description MSc Plymouth for fieldwork 
Organisation University of Plymouth
Country United Kingdom 
Sector Academic/University 
PI Contribution MSc Applied Marine Science student Pernille Forsberg is assisting with the COHBED fieldwork and will also collect her own data for her MSc dissertation. Pernille?s supervisors are Dr Andy Manning and Dr Rob Schindler.
Start Year 2013
 
Description Plymouth - HR Wallingford - Schindler 
Organisation HR Wallingford Ltd
Country United Kingdom 
Sector Private 
PI Contribution Continuation of work with HR Wallingford from previous HEIF-funded research collaboration with UP on characterizing suspended sediments in mixed environments. Emphasis this time on linking ADCP backscatter to known particle characteristics derived from Labsfloc and particle grain sizing.
Start Year 2013
 
Description SIG Challenger Society for Marine Sciences 
Organisation Challenger Society for Marine Science
Country United Kingdom 
Sector Learned Society 
PI Contribution New Special Interest Group (Challenger Society for Marine Science) ?Marine particle fluxes and morphodynamics of the bed? (with Katrien van Landeghem); First meeting in autumn 2014 on mixed sediments (gravel,sand,clay)
Start Year 2014
 
Description BU press release 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact October 2011 - Bangor University press release: "Sticky Stuff: Ocean Sciences research grant to study ripples on mudflats and beaches"
Year(s) Of Engagement Activity 2011
 
Description Country Focus interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact November 2011 - Radio interview for Country Focus (BBC Wales)
Year(s) Of Engagement Activity 2011
 
Description Knowledge transfer to school groups 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience
Results and Impact A background to the sediment dynamics of the local estuary is provided to local school groups who come out into the field to see what research is being done and the importance of the work to local biology/ecology and management of the site.



Space School - school age visitors are introduced to coastal ecosystems and the influence of the tide on such ecosystems. They learn about sediment stability and the organisms which help shape/maintain the environment.



Royal Society Masterclass Series - school age visitors are introduced to coastal ecosystems and the influence of the tide on such ecosystems. They learn about sediment stability and the organisms which help shape/maintain the environment.



Science Discovery Day. Public open day, we will be sharing knowledge on coastal ecosystems with local residents and school groups, allowing hands on experience with some of the equipment we use.

No fixed start/end dates
Year(s) Of Engagement Activity 2014
 
Description Museum of Scotland science fair 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience
Results and Impact Introductions to the public in short talks at the Museum of Scotland annual science fair, March 2013.
Year(s) Of Engagement Activity 2013
 
Description Museum of Scotland science fair 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience Schools
Results and Impact Introductions to the public in short talks at the Museum of Scotland annual science fair, March 2013.
Year(s) Of Engagement Activity 2013
 
Description NOC Liverpool press release 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact January 2012 - NOC News: "A new project looking at estuarine sediment processes - COHBED"
Year(s) Of Engagement Activity 2012
 
Description NOC news article 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Thorne PD, Moate BD and Baas J. 2012 A new project looking at estuarine sediment processes COHBED. NOCnews21(a)2
Year(s) Of Engagement Activity 2012
 
Description NOC news article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Primary Audience
Results and Impact Moate BD and Thorne PD. 2012. Acoustic measurements enter a new dimension. NOCnews22b.
Year(s) Of Engagement Activity 2012
 
Description NOC news article 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Media (as a channel to the public)
Results and Impact Moate BD and Thorne PD. 2012. Acoustic measurements enter a new dimension. NOCnews22b.
Year(s) Of Engagement Activity 2012
 
Description NOCL presentation Manning 2012 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience Participants in your research or patient groups
Results and Impact Manning, A.J.: Invited seminar; presented SiTE research findings to Dr Alex Souza's BLAST Group (Boundary Layer And Sediment Transport) at the National Oceanography Centre - Liverpool (NOC-L), Joseph Proudman Building, Liverpool (December 2012).
Year(s) Of Engagement Activity 2012
 
Description Natur Cymru article 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact October 2011 - Natur Cymru: "Sticky Stuff "
Year(s) Of Engagement Activity 2011
 
Description Science Café interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact November 2011 - Radio interview for Science Café (BBC Wales)
Year(s) Of Engagement Activity 2011
 
Description Science Café interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience
Results and Impact November 2011 - Radio interview for Science Café (BBC Wales) in Hydrolab
Year(s) Of Engagement Activity 2011
 
Description St Andrews school visits 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience Schools
Results and Impact Information on COHBED is included in the University of St Andrews school visits.
Year(s) Of Engagement Activity 2013
 
Description THE announcement 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact October 2011 - Times Higher Education supplement: "Marine Particle Physics"
Year(s) Of Engagement Activity 2011
 
Description Uni Hull press release 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact November 2011 - University of Hull press release: "Stuck in the Mud? University researcher awarded grant to study mudflat, estuarine and coastal environments"
Year(s) Of Engagement Activity 2011