Climate Change: Defining Reference Conditions and Restoring Freshwater Ecosystems - Climate Change Impacts on Freshwater Ecosystems - page 228

Figure 9.9 Topographic maps of the study area in N.E. Twente, the Netherlands, with the
boundaries of the OLU. (a) Recent topographic map, 1 : 10,000 (source: Topografische
Dienst Kadaster, Emmen 2003). The topography is indicated through light grey shading.
Most of the area within the OLU is agricultural pasture, with some arable land and forest.
The Agelerbroek is a wetland nature reserve with forest and meadows. The main stream
system (Tilligterbeek-Hamburgerbeek-Hollandsegraven, actually one stream) connects the
Agerlerbroek area with the Ottershagen area (northern section of the OLU). Both areas are
low-lying plains and the connecting stream system flows through higher terrain. (b) The
boundaries of the OLU depicted on a historical map from 1900, 1 : 25,000 (source:
Topografische Dienst Kadaster, Emmen 1900). The purple areas are the extent of flooding
after extremely high rainfall in 1998. The delineation of the OLU follows the original outlines
of wetlands on the historical map and the extent of the 1998 flooding. (Reproduced with
permission from Journal of Applied Ecology (2008) Vol. 45, pp. 1496-1503.)
The plant communities in the Agelerbroek are typical for stream valleys with
regular flooding and are suitable as a source of species for the restoration areas.
The hydrological and spatial mechanisms to be restored are the natural
flooding frequency of the Ottershagen area and the hydrological connection of
the Agelerbroek reserve with the Hollandsegraven stream network. The
Ottershagen area can be turned into a floodplain again by a different regulation
of stream discharges in the Hollandsegraven sub-catchment, resulting in flooding
events with highest frequency and duration in the winter season. The Agelerbroek
nature reserve, which currently is only partly and rather indirectly connected to
the Tilligterbeek-Hollandsegraven stream system, should be fully connected
again, so that there will be a direct connection between the Agelerbroek and the
Ottershagen areas during periods of flooding. There is an elevation gradient