Beach-dune sediment Exchange and airflow dynamics at a blowout throat during oblique onshore winds

Nicholas O'Keefe, Irene Delgado-Fernandez, Derek Jackson, Paul Aplin

Research output: Contribution to conferencePoster

Abstract

Coastal blowouts are acknowledged as highly effective transport pathways on dune-fringed coasts. Their morphological form is indicative of aeolian transport and the propensity of their topography to modify airflow sufficiently to support transport has been extensively researched [1, 2]. As the evolution of sandy coastlines is governed by sediment exchanges between sub-units of the cross shore profile, blowouts located at the beach-dune interface may play a significant role in dune evolution through enhancing the landward transfer of sediment into the dune field. Although there is a growing number of studies detailing blowout transport, those which encompass synchronous measurement of flow and sediment exchange from the beach into the dune field are rare [3]. Detailed measurements of airflow and sediment transport dynamics at the beach-dune interface of a trough blowout were conducted at Sefton dunes, northwest England. An array of 3D sonic anemometers, co-located with transport sensors were deployed during an oblique onshore wind event. Instantaneous flow and transport dynamics were measured on the back beach, the adjacent upwind foredune and within the throat of the blowout. The resulting morphological response of the blowout surface was captured via pre-and post-event TLS surveys. The importance of alongshore deflected airflow in delivering sediment to the blowout throat area from the beach was highlighted by a linear trend of high magnitude transport intensity across the upwind foredune. Within the throat, levels of transport intensity displayed extremely high spatial and temporal variability across a relatively confined area. Multiple topographically-forced flow modifications were observed. Although incident wind speed remained relatively constant, a sharp 15° onshore directional shift during the experiment resulted in a step change (increase) in transport intensity within the blowout, providing insight into how sediment is first delivered to the throat area and then driven landwards through topographical funnelling (flow compression) of local winds.
Original languageEnglish
Publication statusAccepted/In press - 15 Mar 2018
EventInternational Conference on Aeolian Research - Bordeaux, France
Duration: 25 Jun 201829 Jun 2018

Conference

ConferenceInternational Conference on Aeolian Research
CountryFrance
CityBordeaux
Period25/06/1829/06/18

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blowout
airflow
dune
beach
sediment
dune field
anemometer
coast
sediment transport
trough
wind velocity
compression
topography
sensor
experiment

Cite this

O'Keefe, N., Delgado-Fernandez, I., Jackson, D., & Aplin, P. (Accepted/In press). Beach-dune sediment Exchange and airflow dynamics at a blowout throat during oblique onshore winds. Poster session presented at International Conference on Aeolian Research, Bordeaux, France.
O'Keefe, Nicholas ; Delgado-Fernandez, Irene ; Jackson, Derek ; Aplin, Paul. / Beach-dune sediment Exchange and airflow dynamics at a blowout throat during oblique onshore winds. Poster session presented at International Conference on Aeolian Research, Bordeaux, France.
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abstract = "Coastal blowouts are acknowledged as highly effective transport pathways on dune-fringed coasts. Their morphological form is indicative of aeolian transport and the propensity of their topography to modify airflow sufficiently to support transport has been extensively researched [1, 2]. As the evolution of sandy coastlines is governed by sediment exchanges between sub-units of the cross shore profile, blowouts located at the beach-dune interface may play a significant role in dune evolution through enhancing the landward transfer of sediment into the dune field. Although there is a growing number of studies detailing blowout transport, those which encompass synchronous measurement of flow and sediment exchange from the beach into the dune field are rare [3]. Detailed measurements of airflow and sediment transport dynamics at the beach-dune interface of a trough blowout were conducted at Sefton dunes, northwest England. An array of 3D sonic anemometers, co-located with transport sensors were deployed during an oblique onshore wind event. Instantaneous flow and transport dynamics were measured on the back beach, the adjacent upwind foredune and within the throat of the blowout. The resulting morphological response of the blowout surface was captured via pre-and post-event TLS surveys. The importance of alongshore deflected airflow in delivering sediment to the blowout throat area from the beach was highlighted by a linear trend of high magnitude transport intensity across the upwind foredune. Within the throat, levels of transport intensity displayed extremely high spatial and temporal variability across a relatively confined area. Multiple topographically-forced flow modifications were observed. Although incident wind speed remained relatively constant, a sharp 15° onshore directional shift during the experiment resulted in a step change (increase) in transport intensity within the blowout, providing insight into how sediment is first delivered to the throat area and then driven landwards through topographical funnelling (flow compression) of local winds.",
author = "Nicholas O'Keefe and Irene Delgado-Fernandez and Derek Jackson and Paul Aplin",
year = "2018",
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language = "English",
note = "International Conference on Aeolian Research ; Conference date: 25-06-2018 Through 29-06-2018",

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O'Keefe, N, Delgado-Fernandez, I, Jackson, D & Aplin, P 2018, 'Beach-dune sediment Exchange and airflow dynamics at a blowout throat during oblique onshore winds' International Conference on Aeolian Research, Bordeaux, France, 25/06/18 - 29/06/18, .

Beach-dune sediment Exchange and airflow dynamics at a blowout throat during oblique onshore winds. / O'Keefe, Nicholas; Delgado-Fernandez, Irene; Jackson, Derek; Aplin, Paul.

2018. Poster session presented at International Conference on Aeolian Research, Bordeaux, France.

Research output: Contribution to conferencePoster

TY - CONF

T1 - Beach-dune sediment Exchange and airflow dynamics at a blowout throat during oblique onshore winds

AU - O'Keefe, Nicholas

AU - Delgado-Fernandez, Irene

AU - Jackson, Derek

AU - Aplin, Paul

PY - 2018/3/15

Y1 - 2018/3/15

N2 - Coastal blowouts are acknowledged as highly effective transport pathways on dune-fringed coasts. Their morphological form is indicative of aeolian transport and the propensity of their topography to modify airflow sufficiently to support transport has been extensively researched [1, 2]. As the evolution of sandy coastlines is governed by sediment exchanges between sub-units of the cross shore profile, blowouts located at the beach-dune interface may play a significant role in dune evolution through enhancing the landward transfer of sediment into the dune field. Although there is a growing number of studies detailing blowout transport, those which encompass synchronous measurement of flow and sediment exchange from the beach into the dune field are rare [3]. Detailed measurements of airflow and sediment transport dynamics at the beach-dune interface of a trough blowout were conducted at Sefton dunes, northwest England. An array of 3D sonic anemometers, co-located with transport sensors were deployed during an oblique onshore wind event. Instantaneous flow and transport dynamics were measured on the back beach, the adjacent upwind foredune and within the throat of the blowout. The resulting morphological response of the blowout surface was captured via pre-and post-event TLS surveys. The importance of alongshore deflected airflow in delivering sediment to the blowout throat area from the beach was highlighted by a linear trend of high magnitude transport intensity across the upwind foredune. Within the throat, levels of transport intensity displayed extremely high spatial and temporal variability across a relatively confined area. Multiple topographically-forced flow modifications were observed. Although incident wind speed remained relatively constant, a sharp 15° onshore directional shift during the experiment resulted in a step change (increase) in transport intensity within the blowout, providing insight into how sediment is first delivered to the throat area and then driven landwards through topographical funnelling (flow compression) of local winds.

AB - Coastal blowouts are acknowledged as highly effective transport pathways on dune-fringed coasts. Their morphological form is indicative of aeolian transport and the propensity of their topography to modify airflow sufficiently to support transport has been extensively researched [1, 2]. As the evolution of sandy coastlines is governed by sediment exchanges between sub-units of the cross shore profile, blowouts located at the beach-dune interface may play a significant role in dune evolution through enhancing the landward transfer of sediment into the dune field. Although there is a growing number of studies detailing blowout transport, those which encompass synchronous measurement of flow and sediment exchange from the beach into the dune field are rare [3]. Detailed measurements of airflow and sediment transport dynamics at the beach-dune interface of a trough blowout were conducted at Sefton dunes, northwest England. An array of 3D sonic anemometers, co-located with transport sensors were deployed during an oblique onshore wind event. Instantaneous flow and transport dynamics were measured on the back beach, the adjacent upwind foredune and within the throat of the blowout. The resulting morphological response of the blowout surface was captured via pre-and post-event TLS surveys. The importance of alongshore deflected airflow in delivering sediment to the blowout throat area from the beach was highlighted by a linear trend of high magnitude transport intensity across the upwind foredune. Within the throat, levels of transport intensity displayed extremely high spatial and temporal variability across a relatively confined area. Multiple topographically-forced flow modifications were observed. Although incident wind speed remained relatively constant, a sharp 15° onshore directional shift during the experiment resulted in a step change (increase) in transport intensity within the blowout, providing insight into how sediment is first delivered to the throat area and then driven landwards through topographical funnelling (flow compression) of local winds.

M3 - Poster

ER -

O'Keefe N, Delgado-Fernandez I, Jackson D, Aplin P. Beach-dune sediment Exchange and airflow dynamics at a blowout throat during oblique onshore winds. 2018. Poster session presented at International Conference on Aeolian Research, Bordeaux, France.