Historical and 2023 LiDAR, Photogrammetry, and Multispectral Data of the Dike-in-Dune and Berkheide Dune in Katwijk, NL, in Geomorphological Study of Dune Development in the Netherlands

In the Netherlands, extratropical storm events in the North Sea can reach wind speeds that exceed the threshold speed that defines a hurricane, last a few days, cover a large area, and accompany large fluctuations in tide (mean tide range is 1.7 m in Hoek van Holland) (Ebersole et al., 2022). These storms and areas below sea level in the country are significant contributors to the country's increased flood risk. With extreme weather increasing precipitation, nature-based solutions to flood protection that are resilient to excessive rain, provide a defense to wave and tidal action, and increase slope stability along dikes and dunes, are often sought (Diaz, 2019). One climate-resilient solution is to vegetate dunes with plants and grasses that enhance the functions of the earthen infrastructure. This solution has been widely adopted in the Netherlands and in coastal communities in the United States, including those on the Gulf Coast (Figlus, 2022; Kothius et al., 2018). Like all infrastructure used in flood protection, earthen infrastructure must also be regularly monitored and maintained. Utilizing historical survey data and accounts from authorities responsible for managing the dunes, the current state of vegetated dunes can be assessed. Another method for determining the state of vegetated dunes is to conduct field monitoring and investigations. By utilizing a land-based Light Detection and Ranging (LiDAR) system, and an uncrewed aerial vehicle (UAV) with a multispectral lens, the current topography of the engineered dike-in-dune at Katwik was compared to the natural southern neighboring Berkheide dune, and the Normalized Difference Vegetation Indices (NDVI) of each dune were calculated to determine the health of the vegetation (Zdebski & Grilliot, 2023). Plants such as marram grass (Calamagrostis arenaria) are used to build and stabilize dune systems in the Netherlands. The dike-in-the dune received marram grass transplanted from other Natura 2000 dunes in the area. An analysis of the geomorphological changes to the dike-in-dune and Berkheide dune in Katwijk, since the completion of Kustwerk Katwijk, was conducted with an emphasis on the role of vegetation in these changes. Since there have been no coastal storms that have impacted the dike-in-dune since its construction, the article focuses on dune development for protection against future coastal storms. The research problem addresses the accretion and vegetation health of the dike-in-dune since its construction and how it compares to that of the Berkheide dune for the same period.

Researchers of nature-based solutions in coastal settings can benefit from this data, as can geospatial researchers who work with coastal infrastructure. This data can be used to generate new studies and investigate other aspects that contribute to dune development.