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A field campaign was carried out at a sheltered sandy beach with the aim of gaining new insights into the driving processes behind sheltered beach morphodynamics. Detailed measurements of the local hydrodynamics, bed-level changes and sediment composition were collected at a man-made beach on the leeside of the barrier island Texel, bordering the Marsdiep basin that is part of the Dutch Wadden Sea. The dataset consists of (1) current, wave and turbidity measurements from a dense cross-shore array and a 3ĝ€¯km alongshore array; (2) sediment composition data from beach surface samples; (3) high-Temporal-resolution RTK-GNSS beach profile measurements; (4) a pre-campaign spatially covering topobathy map; and (5) meteorological data. This paper outlines how these measurements were set up and how the data have been processed, stored and can be accessed. The novelty of this dataset lies in the detailed approach to resolve forcing conditions on a sheltered beach, where morphological evolution is governed by a subtle interplay between tidal and wind-driven currents, waves and bed composition, primarily due to the low-energy (near-Threshold) forcing. The data are publicly available at 4TU Centre for Research Data at: 10.4121/19c5676c-9cea-49d0-b7a3-7c627e436541 .

Nature-based strategies, such as wave attenuation by tidal marshes, are increasingly proposed as a complement to mitigate the risks of failure of engineered flood defense structures such as levees. However, recent analysis of historic coastal storms revealed smaller dike breach dimensions if there were natural, high tidal marshes in front of the dikes. Since tidal marshes naturally only experience weak flow velocities (~0-0.3 ms-1 during normal spring tides), we lack direct observations on the stability of tidal marsh sediments and vegetation under extreme flow velocities (order of several ms-1) as may occur when a dike behind a marsh breaches. As a first approximation, the stability of a tidal marsh sediment bed and winter-state vegetation under high flow velocities were tested in a flume. Marsh monoliths were excavated from Phragmites australis marshes in front of a dike along the Scheldt estuary (Dutch-Belgian border area) and installed in a 10 m long flume test section. Both sediment bed and vegetation responses were quantified over 6 experimental runs under high flow velocities up to 1.75 ms-1 and water depth up to 0.35 m for 2 hours. These tests showed that even after a cumulative 12 hours exposure to high flow velocities, erosion was limited to as little as a few millimeters. Manual removal of the aboveground vegetation did not enhance the erosion either. Present findings may be related to the strongly consolidated, clay- and silt-rich sediment and P. australis root system in this experiment. During the flow exposure, the P. australis stems were strongly bent by the water flow, but the majority of all shoots recovered rapidly when the flow had stopped. Although present results may not be blindly extrapolated to all other marsh types, they do provide a strong first indication that marshes can remain stable under high flow conditions, and confirm the potential of well-developed tidal marshes as a valuable extra natural barrier reducing flood discharges towards

Het gebruik van natuur en natuurlijke processen is een innovatieve manier om de waterveiligheid te vergroten en meerwaarde te creëren door natuurontwikkeling en voor recreatie. In deze verkenning is een eerste inventarisatie gemaakt van de kosten en effecten van bestaande Bouwen met de Natuur-projecten in Nederland. Daarnaast is de besluitvorming rondom een aantal van deze projecten in kaart gebracht en zijn succesfactoren geïdentificeerd. Bouwen met de Natuur-projecten voor waterveiligheid leveren meerwaarde, maar dikwijls ook meerkosten ten opzichte van traditionele versterkingen (ca. 120 000 euro per hectare gerealiseerde natuur – met een flinke spreiding over de projecten).

The call for assessing the potential of ‘green’ alongside ‘grey’ solutions for disaster risk reduction is becoming stronger and stronger. With climate change as an important driver the potential for flexible and adaptive management strategies for e.g. flood risk reduction via Nature Based Solutions must be demonstrated in practice. Large Unique Natural Experiments, such as pilot scale implementation of these solutions are needed to show the functioning of these solutions in reality. These pilots are an important step towards a final implementation on the full scale. In this paper we show the importance of being aware of the need for a multi-disciplinary dialogue, and how pilots help to bridge the disciplinary divide that often exists between e.g. civil engineering and ecological sciences, or between decision makers on different government levels. We present the case of a Dutch pilot study on the implementation of natural sandy foreshores in front of an existing dike to improve the strength of this dike. The motto of this pilot was ‘learning by doing’, during the pilot this extended into ‘understanding by doing together’. This proved to be an essential part of how this pilot contributed to the final decision to upscale from this pilot to a full twelve kilometers of dike renovation using a nature based solution. At the same time we discuss other processes that influenced the implementation of this and additional projects using newly constructed sandy shorelines in the same general area.

Coastal zones constitute one of the most heavily populated and developed land zones in the world. Despite the utility and economic benefits that coasts provide, there is no reliable global-scale assessment of historical shoreline change trends. Here, via the use of freely available optical satellite images captured since 1984, in conjunction with sophisticated image interrogation and analysis methods, we present a global-scale assessment of the occurrence of sandy beaches and rates of shoreline change therein. Applying pixel-based supervised classification, we found that 31% of the world’s ice-free shoreline are sandy. The application of an automated shoreline detection method to the sandy shorelines thus identified resulted in a global dataset of shoreline change rates for the 33 year period 1984–2016. Analysis of the satellite derived shoreline data indicates that 24% of the world’s sandy beaches are eroding at rates exceeding 0.5 m/yr, while 28% are accreting and 48% are stable. The majority of the sandy shorelines in marine protected areas are eroding, raising cause for serious concern.

Erratum

Intreerede, uitgesproken bij de aanvaarding van het ambt van hoogleraar Kustwaterbouwkunde aan de Technische Universiteit Delft.

The Netherlands has adopted a new, proactive approach to developing its extensive coastal and river works called ‘building with nature’. Rather than simply minimising or mitigating the environmental impact of harbours, navigation channels, land reclamation and flood defences, the idea is to make use of the dynamics of the natural environment and provide opportunities for natural processes. Existing concepts and ideas have been further developed and tested in a number of full-scale pilot experiments, including sand engines, oyster reefs and waveattenuating forests. This paper describes a number of these experiments along with the preliminary results and lessons learned., Hydraulic Engineering, Civil Engineering and Geosciences

The Netherlands’ strategy to combat coastal erosion since 1990 has been through nourishment, initially as beach nourishments but more and more as shoreface nourishments. In the light of sea level rise projections the yearly nourishment magnitudes continue to increase. In view of this an innovative soft engineering intervention, comprising an unprecedented 21 Mm3 sand nourishment known as the Sand Engine, has recently been implemented in the Netherlands. The Sand Engine nourishment is a pilot project to test the effectiveness and efficiency of a local mega-nourishment as a measure to account for the anticipated increased coastal recession in this century. The proposed concept, a single mega-nourishment, once every 20 years, is expected to be more efficient and effective in the long term than traditional beach and shoreface nourishments, presently being used at the Dutch coast with typically a three to five year interval. While the judgement is still out on this globally unique intervention, if proven successful, it may well become a generic solution for combating sea level rise driven coastal recession on open and vulnerable coasts., Hydraulic Engineering, Civil Engineering and Geosciences

The Netherlands’ strategy to combat coastal erosion since 1990 has been through nourishment, initially as beach nourishments but more and more as shoreface nourishments. In the light of sea level rise projections the yearly nourishment magnitudes continue to increase. In view of this an innovative soft engineering intervention, comprising an unprecedented 21 Mm3 sand nourishment known as the Sand Engine, has recently been implemented in the Netherlands. The Sand Engine nourishment is a pilot project to test the effectiveness and efficiency of a local meganourishment as a measure to account for the anticipated increased coastal recession in this century. The proposed concept, a single mega-nourishment, once every 20 years, is expected to be more efficient and effective in the long term than traditional beach and shoreface nourishments, presently being used at the Dutch coast with typically a three to five year interval. While the judgement is still out on this globally unique intervention, if proven successful, it may well become a generic solution for combating sea level rise driven coastal recession on open and vulnerable coasts., Hydraulic Engineering, Civil Engineering and Geosciences