S.Vos1*, C van Ijzendoorn2, R. Lindenbergh1 and A. de Wulf3
1 Delft, University of Technology, The Netherlands; 2 Oregon State University, The United States; 3 Ghent University, Belgium
* Corresponding author: s.e.vos@tudelft.nl
Introduction
Coastal dunes provide an important role to Dutch society by fulfilling various ecosystem functions. These functions are under pressure because of climate change and urbanization. Dunes are mostly fed by shoreward aeolian sand transport. Increasing urbanization of the beaches in the last decades result in long term asynchronous dune development at certain locations due to the blockage of shoreward sand transport.
Objective and Methods
Three topographic datasets (vos et al., 2023) at various spatio-temporal scales were analyzed to study the effect of beach pavilions on local dune development at Noordwijk beach. First, on the smallest scale (order 100 meters and weeks) topographic changes around two sea containers at Noordwijk beach were studied with terrestrial laser scans. Second, the effect of a full size beach pavilion on the development of about 400 meters of dune was studied with a two year topographic dataset of (bi) monthly permanent laser scans (Kuschnerus et al., 2022). Third, 15 years of annual airborne lidar data along a 2.7-kilometer stretch of the beach/dune system in Noordwijk was used to evaluate the effect of 17 (semi)permanent beach pavilions on decadal dune development
Results
The sea containers experiment showed horseshoe-shaped deposition patterns developing on the leeside of the containers. These depositions followed daily wind changes and over the whole experiment left deposits corresponding to the mean wind direction over the measuring period. Similar patterns were found around the full size beach pavilion, but deposits caused by the wind are harder to distinguish from sand movements due to anthropogenic influences like bulldozing and beach shaping.
The evaluation of the longer termed dataset reveals large variations in dune height and volume in the neighborhood of beach pavilions. Changes in height/volume (Figure 1) vary between 1-8 meter in dune height increase and vary between 0-200 m3 in dune volume increase after 15 years along 2.7 km of coast. An autocorrelation analysis shows that the alongshore variability length scale in dune volume of urbanized dunes can be 10 times smaller than for natural dunes. For about half the beach pavilions, variations in dune height and volume are significantly correlated to the location of the beach pavilion. Here the growth behind the buildings is lower than in the surrounding area which can have consequences for long-term resilience.
Figure 1: Dune development along the Noordwijk coast with (A) the alongshore locations of (semi) permanent beach pavilions, (B) the dune top height development from 2008 until 2023 with the locations of the beach pavilions as red/blue lines and (C) the dune volume development during the same period.
References
Vos, S., van IJzendoorn, C., Lindenbergh, R., de Wulf, A. (2023), Combined datasets for the article "Asynchronous dune development on a Dutch urbanized beach due to buildings and other anthropogenic influences". 4TU.ResearchData. https://data.4tu.nl/datasets/05477395-f4fe-46dc-bed9-89da04c0
Kuschnerus, M., Lindenbergh, R., Lodder, Q., Brand, E., and Vos, S. (2022) Detecting antrophogenic volume changes in cross sections of a seandy beach with permanent laser scanning, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLIII-B2-2022, 1055-1061, https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-1055-2022, 20
