PhD defence: Long-term video monitoring of aeolian activity on a narrow beach

Pam Hage aims for her promotion to clarify the timing of aeolian (wind-blown) transport on a narrow beach and the associated key factors. Coastal dunes grow because of the influx of wind-blown (aeolian) beach sand. Correctly predicting the aeolian sand transport rate on beaches is difficult, as existing models often only use wind speed as a variable under ideal conditions, which are rarely found on sandy beaches. This can cause a mismatch between the existing models and reality.

To clarify the timing of aeolian transport, a video monitoring system was used to qualitatively detect aeolian activity in concert with weather data. Strong onshore wind usually causes limited sand transport, where the expected transport based on the wind speed is large but the video images show only weak signs of transport. Strong winds with unlimited transport happen only when the wind is alongshore. Unlimited transport with smaller wind speeds can have onshore winds, which mainly happens in summer. The effect of beach width and wind direction on the aeolian transport rate were built into a new sand transport model.

The model predicted the timing of (un)limited sand transport reasonably well. According to the model, limited transport is rare, but they can make a significant contribution in limiting the total transport to the dunes. The next step is to test the model for other locations and with in-situ measurements. This improves aeolian sand transport predictions towards the dunes, where it can contribute to protecting the land against marine flooding and to a diverse ecosystem.