Biogeomorphic evolution of wetland and sea level rise: storm and tide interaction with dynamic vegetation patches

Overview

Coastal wetlands are vital natural defences against severe storms, flooding and coastal erosions (Nepf, 2012). They increase coastal resilience and also offer other ecosystem services such as carbon storage and biohabitat (Barbier et al., 2011; Hansen & Reidenbach,).

Past studies of flow-vegetation interaction have been largely focused on homogeneous static vegetation. Studies of dynamics patches are mainly for unidirectional and uniform steady flow (Vandenbruwaene et al., 2011). There is a lack of understanding of the dynamic feedbacks between biological, ecological and physical processes of coastal vegetation in real world setting, which is critical to better manage and protect this disturbance-driven ecosystems in changing climate and accelerated sea-level rise. The marsh vegetation is relatively short in Scotland compared to Spartina anglica dominated marshes further South. With the expected range expansion of clonally spreading Spartina anglica, bio-physical feedbacks in Scottish marshes are likely to change too. In this study, a field observation and sophisticated hydro- and morphodynamic model will be use to investigate the temporal and spatial variation of flow and morphological change within and around dynamic vegetation patches subject to combined wave, tide and current actions. Growth rates and plant traits of Spartina and hydrodynamics at the field sites will be collected by UAV (Unmanned Aerial Vehicle), ADV (Acoustic Doppler Velocimeter), ADCP (Acoustic Doppler Current Profiler) and remote sensing data and used to validate the model predictions. The model hydro- and morphodynamic results will be fed into a colonization model of dynamic vegetation patches to predict the growth in patch size and time evolution of patch configurations which will in turn be incorporated in the updated hydro- and morphodynamic model. The two way coupled flow and vegetation patch dynamics model will be applied to field sites with different tide and wave conditions and current dominance and spread of Spartina anglica in Scotland. The model will be applied to scenarios with various expansion rates of Spartina anglica. The influence of Spartina patch expansion and coalescence on the interplay of biological, ecological and physical processes and the collective performance of vegetation patches as natural coastal defence during storms and in response to sea level rise will also be investigated. The outcome of the proposed bio-physical modelling and field study will provide new insight for the fundamental coupling mechanisms between biological and physical processes of dynamic vegetation patches and biogeomorphic evolution of wetland in response to storms, tide and sea level rise and with relevance to the current spread of Spartina anglica. Further insights into coastal protection function and resilience of contrasting salt marsh vegetation to storm attacks and sea level rise will be provided.

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Image Captions

Figure 1 (a) Scale‐dependent feedback around a vegetation patch is an important factor of plant developments. (b) Aerial photographs showing the time evolution of an intertidal landscape in SW Netherlands from 1989 to 1993 (Figure 1b of Vandenbruwaene et al., 2011). The lateral expansion of patches increase the patch size and decrease the interpatch distance (see patches within ellipse in 1989 and 1993). Flow acceleration and erosion in between the growing patches may then initiate channels and stop the lateral patch expansion (Vandenbruwaene et al., 2011).

Methodology

The growth and evolution of vegetation patches and hydrodynamics at the field sites will be measured by UAV (Unmanned Aerial Vehicle) and ADV (Acoustic Doppler Velocimeter) and ADCP (Acoustic Doppler Current Profiler) and remote sensing techniques. Open source and in-house hydrodynamic and morphodynamic model for vegetation flow developed by the supervisory team will be implemented to simulate the complex flow-vegetation-morphology interactions. The field observations will be used to validate the model predictions.

Project Timeline

Year 1

Literature survey and learning hydrodynamic and morphodynamic models and model setup and executions in first year

Year 2

Field site selection, field observations, data analysis, model applications and validations with existing physical tests and field data, journal and conference paper writing in the second year.

Year 3

Further model-data interpretations for different scenarios to pinpoint mechanisms of bio-physical interaction, thesis writing and journal publications dissemination of research outcomes and public engagement in the third year and after.

Year 3.5

Thesis writing and journal publications and dissemination of research outcomes and public engagement

Training
& Skills

The student will benefit from working with supervisors with different expertise on an interdisciplinary project, develop modelling and field observation skills, and interactions with faculty and students and postdocs at The Lyell Centre for Earth and Marine Science and Technology, Heriot-Watt University, School of Geographical and Earth Sciences, University of Glasgow and the IAPETUS community from 9 institutions and organizations.

The student will be a member of The Lyell Centre, participating in weekly research seminars and meetings. Lyell Centre currently comprises of 11 academic staff, 4 postdocs and 17 PhD students. All students in IAPETUS2 will be enrolled to receive a Postgraduate Certificate in Environmental Methods to demonstrate and recognize the importance of VITAE training. Working in the diverse scientific, geographical and socio-political settings of IAPETUS2 Partner institutions, the student will be trained to become an expert in communicating his/her research within and across disciplines, and to policy makers and the public.

References & further reading

Barbier, E. B., Hacker, S. D., Kennedy, C., Koch, E. W., Stier, A. C., & Silliman, B. R. (2011). The value of estuarine and coastal ecosystem services. Ecological monographs, 81(2), 169-193.
Nepf, H. M. (2012). Flow and transport in regions with aquatic vegetation. Annual Review of Fluid Mechanics, 44, 123-142.
Hansen, J. C., & Reidenbach, M. A. (2012). Wave and tidally driven flows in eelgrass beds and their effect on sediment suspension. Marine Ecology Progress Series, 448, 271-288.
Vandenbruwaene, W., S. Temmerman T. J. Bouma P. C. Klaassen M. B. de Vries D. P. Callaghan P. van Steeg F. Dekker L. A. van Duren E. Martini T. Balke G. Biermans J. Schoelynck P. Meire et al. (2011), Flow interaction with dynamic vegetation patches: Implications for biogeomorphic evolution of a tidal landscape, J. Geophys. Res., 116, F01008, doi: 10.1029/2010JF001788

Further Information

Please contact Professor Qingping Zou at q.zou@hw.ac.uk or Dr. Thorsten Balke at thorsten.balke@glasgow.ac.uk

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