Environmental Sciences Research Institute

Secondary airflow patterns under offshore winds over coastal foredunes

Principle Investigator: Prof. Derek Jackson

Co-Investigators: Prof. Andrew Cooper (Ulster); Dr Andreas Baas (Kings College London)

Post-Doctoral Researcher: Dr Irene Delgado-Fernandez (Ulster)

Research Partners: Dr Kevin Lynch (National University of Ireland, Galway); Dr Meiring Beyers (Klimaat Consulting, Canada)

Funder: UK Natural Environment Research Council (NERC)

Amount: £468K FEC

JPEG - 214.4 kb
Project team at the 2011 EGU meeting, Vienna. From left, Andrew Cooper, Kevin Lynch, Meiring Beyers, Irene Delgado-Fernandez, Derek Jackson and Andreas Baas.

Coastal dunes contain vast amounts of information on past climatic and oceanographic changes and act as important buffers fronting vulnerable low-lying regions of the world. By virtue of their location at the land-ocean interface, they are highly susceptible to environmental change, helping to store sediment which in turn responds rapidly to storms, sea level rise, climatic shifts and human activity. Future predictions of sea-level rise and increased frequency and magnitude of coastal storms do not bode well for communities and ecosystems within, or in proximity to, such systems. Therefore understanding how coastal dunes actually form is crucial in assessing their likely future behaviour.

JPEG - 187.5 kb
CFD modelling output of airflow over coastal foredunes

One of the known criteria for the formation of coastal sand dunes is onshore wind. The presence of large sand dune systems on coasts where the predominant wind blows offshore is therefore difficult to explain and usually they are attributed to the past occurrence of onshore winds and, by implication, subsequent changes in climate. Recent studies at Ulster have however, shown that offshore winds can be deflected or ’steered’ by existing dunes so that their direction changes. This can occur to such an extent that a process known as ’flow reversal’ can arise, whereby the initially offshore wind actually flows onshore at the beach. This can cause sand to be blown from the beach and into the dunes, causing them to grow. Processes such as this may be central in explaining the presence of extensive dunes on coasts where the dominant wind is offshore, but is also important in how dunes recover after periods of wave erosion during storms.

The Natural Environment Research Council (NERC) UK has awarded a £470K project to Ulster to embark on one of the largest projects of its kind to investigate the phenomenon and how it may be crucial in natural recovery of coastlines impacted by storm erosion. Traditionally excluded from calculations of how much sediment enters the coastline, offshore winds may be the ‘forgotten winds’ in beach and dune behaviour. For the first time, Ulster researchers have been able to quantify (rather than simply infer) landward aeolian (wind-blown) sediment transport associated with local steering of offshore directed airflow.

JPEG - 53.5 kb
Cross-shore array of mast-mounted anemometry at Magilligan

The project has assembled an internationally-recognised team of researchers from to use a combination of field measurement of wind and sediment transport coupled with state-of-the-art aerodynamic modelling. The field site, at Magilligan Strand, Northern Ireland, is a coast dominated by offshore winds and contains a variety of coastal dune landforms. Our research methodology involves the application, for the first time, of 3-D computational fluid dynamics (CFD) modelling to natural coastal dunes, coupled with an array of high frequency sediment transport and airflow measurements.

RESEARCH OUTPUT TO DATE:

Journal Articles

Jackson, D.W.T., Beyers, J.H.M., Lynch, K., Cooper, J.A.G., Baas, A.C.W., Delgado-Fernandez, I. (2011) Three-dimensional wind flow behaviour over coastal dune morphology under offshore winds using Computational Fluid Dynamics (CFD) and ultrasonic anemometry. Earth Surface Processes and Landforms, 36, 1113-1134.

Delgado-Fernandez, I., Jackson, D.W.T., Cooper, J.A.G., Beyers, M. Lynch, K., and Baas, A.C.W. (2011) Re-attachment zone characterisation under offshore winds blowing over complex foredune topography. Journal of Coastal Research, SI 64, 273-277.

Beyers, M., Jackson, D.W.T., Lynch, K., Cooper, J.A.G., Baas, A.C.W., Delgado-Fernandez, I. and Dallaire, Pierre-Olivier (2010) Field testing and CFD LES simulation of offshore wind flows over coastal dune terrain in Northern Ireland. In: The Fifth International Symposium on Computational Wind Engineering (CWE2010), Chapel Hill, North Carolina, USA. International Association for Wind Engineering.

Delgado-Fernandez, I., Jackson, D.W.T., Cooper, J.A.G., Baas, A.C.W., Beyers, M. and Lynch, K. (submitted). Field characterization of lee-side flow patterns under offshore winds at a beach-dune system. Journal of Geophysical Research – Earth Surface.

Conference presentations

Jackson, D.W.T., Cooper, J.A.G., Baas, A.C.W., Lynch, K., Delgado-Fernandez, I. and Beyers, M. (2011) Offshore airflow over coastal foredunes: new approaches and methodology. European Geophysical Union, vol. 13, Vienna, 2011 - Oral - Session GM8.2 Beach and Dune.

Beyers, M., Jackson, D.W.T., Cooper, J.A.G., Baas, A.C.W., Lynch, K., Delgado-Fernandez, I. (2011) Comparison of field measurements and CFD simulation of spatial offshore windflow patterns across a foredune system. European Geophysical Union, vol. 13, Vienna, 2011 – Oral – Session GM8.2 Beach and Dune

Delgado-Fernandez, I., Jackson, D.W.T., Cooper, J.A.G., Baas, A.C.W., Lynch, K., and Beyers, M. (2011) Characterization of airflow turbulent zones across a foredune and beach surface under offshore winds: implications for aeolian sediment transport – European Geophysical Union, vol. 13, Vienna, 2011 - Oral - Session GM8.2 Beach and Dune

Delgado-Fernandez, I., Jackson, D.W.T., Cooper, J.A.G., Baas, A.C.W., Lynch, K., and Beyers, M. (2011) Sediment input to lee-side coastal foredunes: preliminary description of frequency and magnitude of potential transport events at Magilligan Strand, Northern Ireland – European Geophysical Union, vol. 13, Vienna, 2011. Poster - GM9.3 Aeolian processes and landforms

Lynch, K., Jackson, D.W.T., Cooper, J.A.G., Baas, A., Delgado-Fernandez, I. and Beyers, M. (2011) Leeside aeolian sediment transport on a sandy beach under offshore winds. European Geophysical Union, vol. 13, Vienna, 2011. Poster – session GM 8.2

Baas, A.C.W., Jackson, D.W.T., Cooper, J.A.G., Delgado-Fernandez, I., Beyers, M. And Lee, Z. (2011) A field study of flow turbulence and sediment transport dynamics on a beach surface in the lee of a coastal foredune under offshore winds. Geophysical Union, vol. 13, Vienna, 2011. Poster – session GM 8.2

Beyers, M., Jackson, D.W.T., Cooper, J.A.G., Baas, A. and Lynch, K. (2010) Field testing and CFD simulation of offshore wind flows over coastal dune terrain in Northern Ireland. The Fifth International Symposium on Computational Wind Engineering (CWE2010), Chapel Hill, North Carolina, USA, May 23-27, 2010.

Jackson, D.W.T., Cooper, J.A.G., Delgado-Fernandez, I., Lynch, K., Baas, A.C.W. and Beyers, M. (2010) Surface wind flow characteristics over foredune and beach topography: 3-D model and high resolution field investigations. Global Sand Seas meeting, Royal Geographical Society, London. 18th October 2010.

Lynch, K., Jackson, D.W.T., Delgado-Fernandez, I., Cooper, J. A.G., Baas, A. C., Beyers, M. (2010) Beach-dune dynamics: Spatio-temporal patterns of aeolian sediment transport under complex offshore airflow. American Geophysical Union, Fall meeting, 13-17 December 2010, Session B33B - Eolian Processes: Biophysical Drivers and Biogeochemical Implications II.

Jackson, D.W.T., Delgado-Fernandez, I., Lynch, K., Baas, A.C., Cooper, J.A.G. & Beyers, M. (2010) Spatial and temporal patterns of airflow across a foredune and beach surface under offshore winds: implications for aeolian sediment transport. American Geophysical Union, Fall meeting, 13-17 December 2010, Session EP21A. Earth and Planetary Surface Processes I: Planetary, Eolian, Remote Sensing.

Baas, A.C., Jackson, D.W.T., Cooper, J.A.G., Lynch, K., Delgado-Fernandez, I., Beyers, M. & Lee, Z.S. (2010) A field study of flow turbulence and sediment transport dynamics on a beach surface in the lee of a coastal foredune under offshore winds. American Geophysical Union, Fall meeting, 13-17 December 2010, Session B22B - Eolian Processes: Biophysical Drivers and Biogeochemical Implications.

Delgado-Fernandez, I., Jackson, D.W.T., Cooper, J.A.G., Baas, A.C., Lynch, K. & Beyers, M. (2010) Reattachment Zone Characterisation under Offshore Winds with Flow Separation on the Lee Side of Coastal Dunes. American Geophysical Union, Fall meeting, 13-17 December 2010, Session B33B - Eolian Processes: Biophysical Drivers and Biogeochemical Implications II.

Lee, Z. S., Baas, A.C., Jackson, D.W.T., Cooper, J.A.G., Lynch, K., Delgado-Fernandez, I. & Beyers, M. (2010) The vertical structure of airflow turbulence characteristics within a boundary layer during wind-blown sand transport over a beach. American Geophysical Union, Fall meeting, 13-17 December 2010, Session B33B - Eolian Processes: Biophysical Drivers and Biogeochemical Implications II.

Delgado-Fernandez, I., Jackson, D.W.T., Cooper, J.A.G., Beyers, M. Lynch, K., and Baas, A.C.W. (2010) CFD Modelling and Field Measuring of Offshore Wind Flows over Coastal Dune Fields at Magilligan Point, Northern Ireland. Young Coastal Science and Engineering Conference, London. March 2010.

Jackson, D.W.T., Cooper, J.A.G., Delgado-Fernandez, I., Lynch, K., Baas, A.C.W. and Beyers, M. (2010) Surface wind flow characteristics over foredune and beach topography: 3-D model and high resolution field investigations. Session No. 120: Dunes, Loess, and Dust: Paleo- and Modern Perspectives on Activation, Stratigraphy, and Processes. Portland Geological Society of America Annual Meeting (31 October - 03 Nov 2010).

Jackson, D.W.T., Cooper, J.A.G., Lynch, K., Baas, A. and Beyers, M. (2009) 3-D Airflow Patterns Over Coastal Foredunes: Implications For Aeolian Sediment Transport. Portland Geological Society of America Annual Meeting (18-21 October 2009).

Jackson, D.W.T., Cooper, J.A.G., Lynch, K., Baas, A. and Beyers, M. (2009) 3D Airflow over coastal foredunes and aeolian sediment transport. Windy Day conference, Department of Geography, University of Loughborough, Department of Geography, Loughborough University, 23rd October 2009.

Jackson, D.W.T., Cooper, J.A.G., Lynch, K., Baas, A.C.W. and Beyers, M. (2009) 3-D Airflow Patterns Over Coastal Foredunes: Implications for Aeolian Sediment Transport. European Geophysical Union, Vienna, Austria