HOW TO USE FLOODPLAINS FOR FLOOD RISK ... - SGGW

Executive summary
processes such as erosion, transportation (usually by
water but sometimes by wind) and deposition or
sedimentation. The main benefits that arise as a result
of these various processes are water quality improvement
and nutrient regulation. The restoration of
wet floodplain soils as opposed to dry floodplain soils
is most significant with regard to biogeochemical functions.
The key functions performed by floodplain wetlands
are:
– nutrient export
– nutrient retention
– carbon retention
– dissolved organic carbon regulation
– trace element storage
– trace element export
When a floodplain habitat located between upland and
a river acts to improve the quality of water draining the
upland and discharging into the river, it is often referred
to as a buffer zone. These can be highly significant
ecotones for the maintenance of good water
quality in a catchment.
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The dynamics of natural river systems strongly influence
floodplain habitats, resulting in very specific
complexes of ecosystems and habitats. The biodiversity
of any given area depends upon the diversity of
the physical and chemical environment and is thus
enhanced by the presence of as many gradients as
possible. The differentiation of the landscape by naturally
functioning river systems enhances biodiversity
on both the landscape and the local scale. Along
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physical gradients (e.g. altitude and soil composition),
specialised communities and species of plants and
animals have evolved through close interaction with
physical factors.
In a European context, up to 80 percent of all the existing
species of wild plants and animals are, at least
in part, associated with river-influenced landscapes.
River regulation has resulted in the widespread loss of
many of these important and now rare habitats. Also,
the fragmented occurrence of these habitats means
that natural riverine corridors for migration of various
species have been lost. Restoration of natural flooding
on floodplains can result in the restoration of diverse
habitats and migration corridors.
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In today’s European market economy, the fact that
flooding is a vital part of a natural river system is usually
ignored and floodplains are used for economic
functions ranging from intensive agriculture to industrial
development and housing. Flooding is often not
acceptable or at best regarded as a severe hazard or
nuisance, limiting human activities in an area. It is important
to distinguish between flood management in
floodplains that are not used intensively and flood
management in highly developed floodplains because
the socio-economic aspects of these two extremes
are quite different. In floodplains with minimal human
uses ((semi-) natural systems), the likelihood that
costly damage will occur is much lower than in highly
populated areas, while flooding in intensively used
floodplains is likely to result in much greater damage
and economic loss.
Figure 4. Diverse habitats along the Sauga River, Estonia
Photo: E. de Bruin/Grontmij
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