STRUCTURAL ADAPTATIONS
(Canada in a
Changing Climate)
In contemplating structural adaptations, one should consider whether the system will be capable of dealing with the projected hydrological changes, as well as the economic, social and ecological costs of the adaptation.
Physical infrastructure, such as dams, weirs and drainage
canals, has traditionally served as one of the most important adaptations for
water management in Canada.
There are conflicting opinions, however, on the potential of building new
structures for climate change adaptation.
Given the substantive environmental, economic and social costs
associated with these structures, many experts advocate avoiding or postponing
the
construction of large-scale infrastructure until there is
greater certainty regarding the magnitude of expected hydrological changes. On
the other side of the coin is the fact that water infrastructure improves the
flexibility of management operations, and increases a system’s capacity to
buffer the effects of hydrological variability. In the Peace
River, for example, stream regulation will allow operators to
potentially offset the effects of climate
change on freeze-up dates by reducing winter releases.
Similarly, communities in the southern Prairies can use small-scale water
infrastructure to increase water storage through snow management, and reduce
regional vulnerability to drought.
Most existing water management plans, as well as
water-supply and -drainage systems, are based upon historic climatic and
hydrological records, and assume that the future will resemble the past. Although these systems should be sufficient
to handle most changes in mean conditions associated with climate change over
the next couple of decades,
management problems are likely to arise if there is an
increase in climate variability and the occurrence of extreme events. Case studies
in Ontario
indicate that increases in the intensity of precipitation events have the
potential to increase future drainage infrastructure costs and decrease the
level of service provided by existing systems (Box 4).
BOX
4: How vulnerable is our
infrastructure?
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Since the majority of urban water drainage systems are
designed based upon historical climate records, a change in precipitation
patterns may cause these systems to fail.
More intense precipitation events are expected to decrease the level
of service that existing drains, sewers and culverts provide, and increase
future drainage infrastructure costs.
While making the necessary changes (e.g., increasing pipe sizes) would
be expensive, the overall costs are expected to be lower than the losses that
would result from not adapting. For
example, insufficient pipe sizes would lead to an increase in sewer backups,
basement flooding and associated health problems.
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Several studies suggest that the design of water management
systems should focus on thresholds, such as the point at which the storage
capacity of a reservoir is exceeded, rather than mean conditions. Thresholds
can induce nonlinear and therefore less predictable responses to climatic
change, which would significantly stress the adaptive capacity of water
resource systems.
In many cases, modification of existing infrastructure operations,
rather than the introduction of new structures, will be an effective adaptation
option. For example, models indicate
that the Grand River basin will be able to adapt to all
but the most severe climate change scenarios through modifications in operating
procedures and increases in reservoir capacity.
A drainage infrastructure study of North
Vancouver suggests that the system can be adapted to
more intense rainfall events by gradually upgrading key sections of pipe during
routine, scheduled infrastructure maintenance. Adaptations such as these can be
incorporated into long-term water management planning.
