The influence of coastal morphology on wind dynamics

D Jarmalavičius,D Pupienis,G Žilinskas,J Satkūnas

doi:10.3176/earth.2012.2.04

Abstract

An analysis of the dynamics of wind velocity along the Baltic coast of Lithuania is presented, based on data collected during field experiments in the summer, fall and winter of 1999-2001 and 2007-2009 at several sites (Būtingė, Saipiai, Smiltynė, Juodkrantė, Pervalka and Nida). The locations were chosen in order to encompass a wide spectrum of beach and dune ridge morphology. The relationship between wind velocity dynamics and coastal morphology was established, based on measurements of the slope angle, height and shape of the dune crest, as well as measurements of the morphology of the area behind the foredune ridge. On the basis of a comparison of near-surface wind velocity patterns, shear velocity (U*) and surface roughness length (z0) were calculated. It was determined that U* decreases from the middle of the beach towards the foredune toe, then increases towards the crest of the foredune and decreases down the lee slope. A direct correlation exists between U* and the stoss slope inclination, and the relative height of the foredune. Surface roughness length also increases from the beach towards the foredune crest.

Highlights

The action of wind on exposed sediments and friable rock formations causes erosion and entrainment of sediment particles
Quite often the potential of sand transport is estimated on the basis of the characteristic of the wind recorded on the beach or at the nearest meteorological station, regardless of the transformation of the wind over dunes
Most of the existing studies are based on the measurements carried out in one coastal profile, reflecting the specific features of a particular coastal sector (Arens et al 1995; Van Boxel et al 1999; Hesp et al 2009) or investigating near-surface wind transformation in boundary layer conditions according to wind tunnel investigation (Wiggs et al 1996) and numerical modelling (Parsons et al 2004)

Summary

Introduction

The action of wind on exposed sediments and friable rock formations causes erosion (abrasion) and entrainment of sediment particles. Dune topography is one of the main factors affecting near-surface wind flow transformation and sand transport. The assessment of the dynamics of wind velocity in coastal areas has become an important research subject (Keevallik 2008) It allows estimation of the potential of sand transport (Svasek & Terwindt 1974; Kroon & Hoekstra 1990; Bauer et al 1996; Davidson-Arnott & Law 1996; Gares et al 1996; Nordstrom et al 1996; Žilinskas et al 2001), determination of the peculiarities of dune formation and development (Robertson-Rintoul 1990; Fraser et al 1998; Li et al 2004; Houser et al 2008) and assessment of variations in coastal processes (Orviku et al 2003). The main objective of the present study is to evaluate the influence of foredune morphology on wind flow transformation in different coastal sectors, covering the widest possible spectrum of foredune morphology

Objectives

Methods

Findings

Conclusion