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

The roles of floodplains restoration contributes to nature conservation
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Water is the source of life for humans, animals and
plants. A human being can survive without drinking
water for only a few days. Despite this need for water,
many water sources such as wetlands historically
have been associated with fever and poor health. This
perception lasted well into the 19th century when the
precise relation between infected water sources and
diseases such as cholera became known. Currently a
large group of major water and sanitation related diseases
are ascribed to microorganisms. In tropical
countries these microorganisms form by far the larg-
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est threat to health, although various waterborne
chemical pollutants (e.g. arsenic, lead etc.) can also
cause considerable health problems. While many
health benefits can arise from floodplain restoration
schemes (e.g. the use of recreational areas, improved
water quality etc.) it is important to consider that some
aspects of floodplain restoration can potentially be
deleterious to human health. Generally health threats
arise because of the association of water with waterborne
diseases. The nature of the threats varies depending
on the potential type of restoration scheme
proposed and the associated likely causes of poor
health. In addition, problems can arise from the encouragement
of ‘nuisance’ species to an area, such
as mosquitoes, which not only can be annoying to the
public but in some situations can be associated with
specific health risks (Boxes 33 and 34).
Mosquitoes are often regarded as a nuisance to people. They are, however, only a nuisance when they
bite and form large swarms. There are several species from which only a few are of a biting kind. In general
the Chironomidae (dancing mosquitoes), the Calucidae (stinging mosquitoes) and the Ceratopogonidae
(midges) are considered as annoying.
Figure 45. Mosquitoes can transfer diseases to humans
Photo: RIZA
Nuisance from Chironomidae?
Populations of these species vary from year to year. The mechanism behind this is unclear, but it is
known that in constructed lakes and ponds in which a transition from salt to fresh water exists, large
populations occur more frequently due to a lack of grazing by their natural predators. Preventing these
swarms is not easy. Currently no regulating measures have been developed. High quality, clear water
promotes greater species diversity and therefore more predators are likely to exist, and the occurrence
of swarms is likely to be reduced.
Nuisance from Calucidae?
These mosquitoes occur mostly in still, shallow water and are resistant to temporary drainage. In general
if the ecosystem is in balance the quantity of mosquitoes is low and hardly any nuisance occurs. By constructing
new wetlands this equilibrium often is temporarily disturbed and large swarms can occur. Simple
measures such as creating flow will decrease the occurrence of this species. Also creating woodlands
as a barrier between breeding places and urban areas is an easy and effective measure.
Nuisance from Ceratopognidae (midges)?
Midges occur in fresh and saltwater swamps and peatlands. Midge bites can be painful and cause considerable
itching. Effective measures to reduce the occurrence of midges associated with wetlands have
not yet been developed.
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