Sanders, Marlies 
  
REMOTELY SENSED HYDROLOGICAL ISOLATION TO SUPPORT SUSTAINABLE USE OF 
FENS IN THE NETHERLANDS 
Marlies Sanders 
Alterra, Green World Research 
m.e.sanders@alterra.wag-ur.nl 
Technical Commission VII-3 
KEY WORDS: Ecosystems, Integration, Modelling, GIS, Remote sensing, Hydrology, Nature conservation, Wetlands 
ABSTRACT 
In the twentieth century many fens in The Netherlands were reclaimed for agriculture. The few fens left have a large 
biodiversity, which make them valuable nature reserves. Land use influences largely the vegetation structure, plant 
species composition and hydrology. Careless use of fens is a huge tread to their biodiversity. Aim of this study was to 
investigate the possibilities of remote sensing and GIS to define a hydrological model that supports sustainable land use 
and management practices. Remote sensing supplied hydrological parameters. A combination of aerial photo 
interpretation and digital image analyses of scanned false colour aerial photographs was applied. The results were input 
of a geographical model for hydrological isolation defined in GIS. The modelled hydrological isolation pattern was 
evaluated by comparing it to distribution patterns of plant species. The species represent a certain plant community, 
management practice and level of hydrological isolation. Statistical tests explored the relationship between observed 
plant species sites and the hydrological and management variables. Hydrological isolation and management turned out 
to be significant in explaining plant species habitat. Hence, the influence of management practices and land use on 
species habitat was succesfully assessed with remote sensing and GIS. This implied the model’s suitability to consider 
the pros and cons of land use changes and management practices regarding biodiversity. The method should be refined 
and applied to more plant species to become a more general applicable instrument. 
1 INTRODUCTION 
Dutch inland wetlands are characterized by peat 
formation under specific geomorphological (floodplain) 
and climatic settings (mean temperature and 
s De Weerribber precipitation) and human impacts (Verhoeven et al., 
1992). Human impact, specifically the peat cutting and 
dredging in the 18th and 19th centuries formed a 
landscape of extensive rectangular peat ponds (ca. 30 by 
1000 m) called petgaten (Figure 2). Narrow strips of the 
original peat, used for making the turves, separate the 
petgaten. After the petgaten were abandoned, a process 
of terrestrialization from open water to reed fen began: 
the vegetation formed a floating raft (Haans & 
Hamming, 1962). During the 20th century most of the 
Figure 1. Location of De Weerribben in The fens were drained and reclaimed for agricultural use. De 
Netherlands Weerribben (3600 ha, Figure 1), now a nature reserve, is 
one of the remaining fen areas in the north of The 
Netherlands (6? 0 E and 52° 45 N). 
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In fens plant species composition is determined by land use and hydrology, particularly by water chemistry such as nutrient 
status (Verhoeven et al., 1988; Van Diggelen, 1996). Present land use comprises nature conservation, water retention, 
recreation and the harvesting of natural resources such as reeds and fish. Awareness raising and restricted access are the 
most important measures applied to control disturbance and pollution from visitors. Fishery and reed cutting is subject to 
strict regulations, to ensure sustainable use within the reserve. If harvested in summer, the vegetation is able to develop 
into a species-rich fen meadow. It is considered important to remove the hay, to reduce nutrient availability. Cutting reeds 
in winter (Figure 3) benefits reed production. Much water in De Weerribben is seeped away because of the low water level 
of the surrounding polders. This induced a water deficit for reed cultivation. To keep reed production profitable, dikes were 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 1309