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Airflow and aeolian sediment transport patterns within a coastal trough blowout during lateral wind conditions

Smyth, T.A.G., Jackson, D.W.T. and Cooper, Andrew (2014) Airflow and aeolian sediment transport patterns within a coastal trough blowout during lateral wind conditions. EARTH SURFACE PROCESSES & LANDFORMS, 39 . pp. 1847-1854. [Journal article]

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DOI: 10.1002/esp.3572

Abstract

Blowouts are depressions that occur on coastal dunes, deserts and grasslands. The absence of vegetation in blowouts permits high speed winds to entrain and remove sediment. Whereas much research has examined patterns of wind flow and sediment transport on the stoss slopes and lee of sand dunes, no study has yet investigated the connections between secondary air-flow structures and sediment transport in a blowout where zones of streamline compression, expansion and steering are less clearly delineated. In this study we investigated the variability of sediment flux and its relation to near-surface wind speed and turbulence within a trough blowout during wind flow that was oblique to the axis of the blowout. Wind flow was measured using six, 3-D ultrasonic anemometers while sediment flux by eight sand traps, all operating at 25 Hz. Results demonstrated that sediment flux rates were highly variable throughout the blowout deflation basin, even over short distances (< 0.5 m). Where flow was steadiest, flux was greatest. Consequently the highest rates of sediment transport were recorded on the erosional wall crest where flow was compressed and accelerated. The strength of correlation between sediment flux and wind parameter improved with an increase in averaging interval, from 10 seconds to 1 minute. At an interval of 10 seconds, however, wind speed correlated best with flux at seven of eight traps, whereas at an interval of 1 minute Turbulent Kinetic Energy (TKE) provided the best correlation with flux at six of the eight traps. Correlation between sediment flux and wind parameters was best in the centre of the blowout and poorest on the erosional wall crest. The evidence from this paper suggests, for the first time, that TKE may be a better predictor of sediment transport at minute scale averaging intervals, particularly over landforms where wind flow is highly turbulent.

Item Type:Journal article
Faculties and Schools:Faculty of Life and Health Sciences > School of Geography and Environmental Sciences
Faculty of Life and Health Sciences
Research Institutes and Groups:Environmental Sciences Research Institute > Coastal Systems
Environmental Sciences Research Institute
ID Code:29118
Deposited By: Professor Derek Jackson
Deposited On:04 Apr 2014 12:15
Last Modified:24 Mar 2015 15:22

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