The Dutch coast is one of the most heavily nourished coasts globally. An average of 12 mln. m3 is annually added to the coastline of only 432 km for dynamic coastline conservation. This study provides an overview of the operational aspects of the more than 300 nourishments for coastline maintenance that have been performed since the 1990s and discusses the evolution of the nourishment approach and lessons learned with regard to the nourishment design. The first nourishments were beach and dune nourishments to repair local beach and dune erosion. In the 1990s the nourishment efforts increased when nourishing the coastline was set in policy as the formal strategy to dynamically preserve the coastline. Simultaneously shoreface nourishments emerged, which aim to feed the coast gradually over a longer period than beach nourishments. In 2001 the volume of sand used for nourishments increased from 6.4 to 12 mln. m3 per year, to enable the coastal zone to stay in equilibrium with sea level rise. Channel wall nourishments were introduced around that time because they can slow down the landward migration of tidal channels and can accommodate large volumes of sediment. Nowadays, underwater nourishments are preferred because of the lower costs associated, but the decision for a beach, shoreface, or channel wall nourishment also depends on the morphology, the local setting, and the purpose of the nourishment. All nourishments combined have succeeded in conserving the coastline at its desired position over the past 30 years.@en

Coastal areas world wide are highly dynamic areas, subject to continuous deformation processes. Both natural and anthropogenic processes constantly cause changes at various spatial scales. Sandy beaches in the Netherlands fall under a regulation, according to which moving sand is permitted, if the volume change remains below a certain threshold. The threshold holds for volume changes within a cross section of 1 m width of the beach. The enforcement of this rule is currently labor intensive, because monitoring generally happens only on a yearly basis, or incidental and non-quantitative. Improved observation capabilities with remote sensing are advancing the supporting technology for this kind of regulations. Permanent laser scanning is a potential tool for monitoring and quantifying volume changes of a section of the beach. We develop and implement methodology to extract time series of volume change with respect to a reference date of 01-01-2020 covering January 2020 until the end of April 2020. The method is applied on point cloud data from a permanent laser scanner on the coast of Noordwijk, The Netherlands. We analyse the time series for incidents, where the threshold in volume change is passed, and find all shortest intervals during which the threshold is passed. Then we analyse potential underlying cause in order to support not only enforcement, but also evaluation of the current regulation. This will ultimately help to work towards a better understanding of the influence of small scale human activities on coastal development.

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Sediment transport is a key element in intertidal beach morphodynamics, but measurements of sediment transport are often unreliable. The aim of this study is to quantify and investigate cross-shore sediment transport and the resulting topographic changes for a tide-dominated, sandy beach. Two fortnight-long field experiments were carried out during which hydrodynamics and sediment dynamics were measured with optical and acoustic sensors, while the beach topography was surveyed with a permanent terrestrial laser scanner. Suspended sediment was generally well-mixed and currents were largest at approximately 1.5 m above the bed, which resulted in a peak in sediment transport at 1/3 of the high tide level. The mean transport direction was onshore during calm conditions (wave height < 0.6 m) thanks to tidal currents and offshore during energetic conditions due to undertow. Oscillatory transport was always onshore because of wave asymmetry but it was subordinate to mean transport. The intertidal zone showed an alternation of erosion and accretion with formation of morphological features during energetic (no storm) conditions and smoothening of the morphology during calm conditions. A good qualitative and quantitative agreement was found between the daily cross-shore suspended load and beach volume changes, especially during calm conditions.@en