Can sand nourishment material affect dune vegetation through nutrient addition?

In the Netherlands it is common to nourish the coastline with sand from the seabed. Foredunes are replenished with sand from the beach and can be transported further into the dune area. We investigated whether nourishment material alters the phosphorus (P) content of dune soil and the nitrogen (N):P ratio of dune vegetation in two areas: a mega sand nourishment with fixed foredunes (SE) and a traditional sand nourishment with dynamic foredunes (NWC). Four zones were considered: beach (zone 1), frontal foredunes (zone 2), foredunes crest (zone 3) and inner dunes (zone 4). We estimated the characteristics of fine (< 250-μm) and coarse (250–2000 μm) sand. Total P, P speciation and available P of SE and NWC were similar until zone 4. Zone 1–3 consisted mainly of coarse sand, whereas the sand in zone 4 was finer with higher amounts at NWC. Iron (Fe) bound P was comparable for fine and coarse sand in zone 1–3, but high contents were present in zone 4. In zone 1–3, calcium (Ca) bound P was mainly found in the fine fraction, which was abundant in the coarse fraction of zone 4. After a period of 4 years, the effect of dynamic dunes on P fractions and dune plant species was not apparent yet, although inblowing sand mainly consisted of fine sand with high contents of Ca-bound P. This may change over time, especially in dynamic dunes with higher eolian activity of fine sand. Consequently, pH buffering of the soil may increase because of a higher Ca‑carbonate content, which leads to decreased solubility of Ca-bound P and low P availability for the vegetation. Both low P availability and high buffering capacity are known environmental factors that facilitate endangered dune plant species

Can sand nourishment material affect dune vegetation through nutrient addition?

In the Netherlands it is common to nourish the coastline with sand from the seabed. Foredunes are replenished with sand from the beach and can be transported further into the dune area. We investigated whether nourishment material alters the phosphorus (P) content of dune soil and the nitrogen (N):P ratio of dune vegetation in two areas: a mega sand nourishment with fixed foredunes (SE) and a traditional sand nourishment with dynamic foredunes (NWC). Four zones were considered: beach (zone 1), frontal foredunes (zone 2), foredunes crest (zone 3) and inner dunes (zone 4). We estimated the characteristics of fine (< 250-μm) and coarse (250–2000 μm) sand. Total P, P speciation and available P of SE and NWC were similar until zone 4. Zone 1–3 consisted mainly of coarse sand, whereas the sand in zone 4 was finer with higher amounts at NWC. Iron (Fe) bound P was comparable for fine and coarse sand in zone 1–3, but high contents were present in zone 4. In zone 1–3, calcium (Ca) bound P was mainly found in the fine fraction, which was abundant in the coarse fraction of zone 4. After a period of 4 years, the effect of dynamic dunes on P fractions and dune plant species was not apparent yet, although inblowing sand mainly consisted of fine sand with high contents of Ca-bound P. This may change over time, especially in dynamic dunes with higher eolian activity of fine sand. Consequently, pH buffering of the soil may increase because of a higher Ca‑carbonate content, which leads to decreased solubility of Ca-bound P and low P availability for the vegetation. Both low P availability and high buffering capacity are known environmental factors that facilitate endangered dune plant species

Predicting monthly to multi-annual foredune growth at a narrow beach

An open-source quantitative model for predicting coastal foredune growth at monthly to multi-annual (meso)temporal scales is developed. The model builds on the established fetch framework as a surrogate for the complex micro-scale aeolian processes on the beach, to which rain and groundwater-induced spatiotemporal surface moisture dynamics are added as factors limiting aeolian sand supply to foredunes. The model shows great skill in an application at Egmond aan Zee, The Netherlands, with a predicted growth of 16.5 m3/m/yr comparing favourably to the observed growth of 17.3 m3/m/yr. Rain, surface moisture dynamics as well as beach width reduction by storm-induced elevated sea levels are shown to be important factors that jointly reduce meso-scale sand supply below the potential (i.e., unlimited) maximum, in our case study by almost 5 m3/m/yr. These factors are most relevant for strong (here, above 15.5 m/s) onshore winds. Consistent with expectations from the literature, meso-scale foredune growth results primarily from moderately strong (9.5–12.5 m/s) shore-oblique winds, which are frequent and do not result in supply-limited conditions. At the study site these winds are most common in winter and hence foredune growth is predicted to vary seasonally, consistent with the observations. Because of the promising results we believe that our model has potential for quantifying how quickly a foredune can recover after an episodic erosion event because of storm waves

Predicting monthly to multi-annual foredune growth at a narrow beach

An open-source quantitative model for predicting coastal foredune growth at monthly to multi-annual (meso)temporal scales is developed. The model builds on the established fetch framework as a surrogate for the complex micro-scale aeolian processes on the beach, to which rain and groundwater-induced spatiotemporal surface moisture dynamics are added as factors limiting aeolian sand supply to foredunes. The model shows great skill in an application at Egmond aan Zee, The Netherlands, with a predicted growth of 16.5 m3/m/yr comparing favourably to the observed growth of 17.3 m3/m/yr. Rain, surface moisture dynamics as well as beach width reduction by storm-induced elevated sea levels are shown to be important factors that jointly reduce meso-scale sand supply below the potential (i.e., unlimited) maximum, in our case study by almost 5 m3/m/yr. These factors are most relevant for strong (here, above 15.5 m/s) onshore winds. Consistent with expectations from the literature, meso-scale foredune growth results primarily from moderately strong (9.5–12.5 m/s) shore-oblique winds, which are frequent and do not result in supply-limited conditions. At the study site these winds are most common in winter and hence foredune growth is predicted to vary seasonally, consistent with the observations. Because of the promising results we believe that our model has potential for quantifying how quickly a foredune can recover after an episodic erosion event because of storm waves

Comment on ‘Is ‘re-mobilisation’ nature restoration or nature destruction? A commentary’ by I. Delgado-Fernandez, R.G.D. Davidson-Arnott &amp; P.A. Hesp

In their recently published paper, Delgado-Fernandez et al. (2019) critically review the limitations and dangers of the relatively recent shift towards dune rejuvenation management in North-western Europe. We would like to comment on the paper from the Dutch perspective.Coastal Engineerin