Title

Short communication: High-frequency bed elevation measurements using ultrasonic distance sensors

Document Type

Article

Publication Date

2012

Publication Title

Aeolian Research

Volume

6

First Page

75

Last Page

81

DOI

10.1016/j.aeolia.2012.08.005

Keywords

Accretion, Bed elevation, Erosion, Methodology

Abstract

Ultrasonic distance sensors can be used to measure changes in bed elevation at high-resolution and frequency. These non-contact sensors have a conservative resolution of ∼0.1. mm and are sufficiently ruggedized to be placed within the saltation layer, without affecting the flow or causing scour. A cross-shore transect of ultrasonic distance sensors was deployed across the backshore and seaward face of a recovering blowout and foredune at Padre Island National Seashore, Texas to demonstrate the ability of these sensors to measure bed elevation change in aeolian environments. Measuring bed elevation at 1. min intervals over 500. h reveals episodic and dramatic changes in bed elevation in response to both onshore and offshore winds. Consistent with pre- and post-surveys, the change in bed elevation ranged from a couple of centimeters at the majority of station to over 26. cm near the foredune crest. Bed elevation change exhibited a weak covariance along the instrumented transect and wavelet analysis reveals a transition from high-frequency changes (every 12-40. h) in the backshore to low-frequency changes (every 120. h) along the seaward face of the foredune. The ability to measure bed elevation at high-frequency and resolution provides an opportunity to improve sediment transport estimates and ultimately relate erosion and deposition to specific transport events. © 2012 Elsevier B.V.