Erosion of dunes is in general associated with wind erosion. However, research shows that water
erosion also plays an important role in erosion of dunes. Water repellency plays an important role in
causing water erosion. A water repellent soil has major consequences as reduced infiltration, higher
runoff and therefore higher erosion rates. It is widely accepted among scientists that vegetation and
organic matter play a central role in causing water repellency. However, a lot is still unknown about
the relationship between water repellency and vegetation development. The overall objective of this
research is to develop a more comprehensive understanding of the occurrence, distribution and
hydrological consequences of water repellent soils along a vegetation gradient in the dunes of the
Dutch island Texel. This research is highly relevant, since water repellency has never been studied
before along a vegetation gradient on the Wadden Islands. For this research five different plots along
a vegetation gradient have been examined for the extent of water repellency, organic matter and
vegetation cover. Rain simulations were carried out to determine the hydrological parameters
(infiltration capacity, runoff and erosion). It was found that the strength of water repellency increases
along the vegetation gradient from young dunes with a low vegetation cover till old dunes with a high
vegetation cover. There was no clear indication that infiltration decreased and runoff increased along
the vegetation gradient. It was found that erosion is very variable and dependent on many factors.
The relationship between runoff and erosion seems to be very difficult. Moreover it was found that
vegetation and-/or litter cover limit soil erosion. Water erosion on older highly vegetated and
extremely repellent plots was therefore lower than expected. The highest erosion rates did occur on
a less vegetated and less repellent plot. In addition it was found that the loss of top soil due to
repeating high erosion rates after a high rain intensity has a negative effect on the strength of water
repellency. Lastly, a significant positive correlation between the runoff rate and the organic matter
content of the sediment was found.
Keywords: water repellency, (water) erosion, infiltration capacity, dunes, Texel.