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EXECUTIVE SUMMARY
Introduction
This study has been commissioned by Scottish Executive
Environment Group, Air Climate and Engineering Division as
a short scoping study to identify and assess the financial
and non-financial impacts of extreme weather experienced in
Scotland during August 2004.
The objective of this report as outlined in the research
specification is to use the best available information and
where appropriate robust and credible assumptions to:
- Identify the full range of impacts of the extreme
weather event - financial and non-financial; and
- Estimate the cost of the recent extreme weather
event, and
- Propose a method to enable the costs of any such
future events to be captured with a greater degree of
accuracy.
August 2004
Only limited data was made available within the
timescale of the project and some of the estimates are made
on a very limited data set. August is traditionally a high
precipitation month although extensive flooding is less
common due largely to the river levels being fairly low and
higher rates of evapo-transpiration associated with summer
conditions. August 2004 was judged to be exceptionally wet
and reported rainfall and river flows well above the
monthly average.
Whilst the peak flows in the larger rivers in August
2004 are not large when assessed against the annual flood
series they would appear to be locally significant for
August. The rainfall is similarly distributed. This would
also suggest that for smaller catchment and the areas
affected by landslides where there are no gauges either
within the catchment that the event could be more
severe.
Assessing Future Flood Severity
In terms of quickly assessing the flood severity the
following steps could be taken:-
- The hydrological summary is rapidly available after
a flood event and could be used in assessing return
periods and event's severity. Data is summarised from
SEPA and
MET office gauges and compared using
standard methods and hydrometric areas.
SEPA use the hydrological summary to
ascertain return periods in publications such as their
bathing water report
1.
- The primary hydrometric data can be analysed in
detail, this could be undertaken by
SEPA and provided to the Executive
or undertaken by a third party on supply of the long
term records. There would appear to be resource issues
in providing the original data. Some data in key areas
affected by the August floods took 4 months to be made
available. If this analysis is likely to be a regular
requirement then resourcing issues may need to be
addressed. This could be achieved by increased staff or
placing data in the public domain through the web. The
data is currently held in a number of databases and
some of the analysis required could be via standard
query within these databases.
- A software tool to provide information on flood
severity could readily be written.
Flood reports
After the flood in August 2004, Scottish Executive
requested local authorities to provide information on the
flooding as it occurred. The information submitted is kept
in a file and varies in format. In order to improve the
establishment of future flooding information, producing a
standard proforma would allow timely and consistent data
collection. This could be easily completed, perhaps on line
by an agency to provide data and could be included in any
biennial return.
SEPA have recorded a number of
historical outlines. Scottish Water collects data reported
to its customer careline and is therefore often the best
dataset in urban areas; however it is property specific and
can be considered sensitive. Fire Brigade, Police and Local
Authorities also record flooding incidences. This
information is not collated centrally and therefore this
leaves an important gap in our understanding of flood risk,
particularly in economically important areas. The costs
associated with urban and sewer flooding are significant
and although often considered in isolation by the relevant
authorities the costs to the nation need to be aggregated
to determine an overall cost.
It is recognised that it is difficult to mobilise staff
to record areas of flooding in urban areas before wrack
marks or water marks are removed in clean up operations.
Therefore it is necessary to know which authority will be
responsible for collecting this data and how it will be
resourced in advance.
Economic costs
The overall damages have been estimated at between £7.2
million and £31 million. With the mid estimate at £18
million, this is equivalent to uncertainty (around the mid
estimate) of between 60% and 70%. The non-money impacts are
expected to be small and are unlikely to significantly
affect the damage estimates, such that it may be considered
that the 'true' damages fall within the above range. To
improve these cost estimates, much more quantitative data
is required on the extent and effects of flooding. In
particular, key information that should be recorded during
and after flood events includes;
- number of residential properties flooded (some
information was available, but this was not
complete);
- number and type of commercial properties flooded
(this is a key source of uncertainty and more research
may also be required into the damages that are
experienced by commercial properties);
- number of weeks that people have to move out of
their property while it is being repaired (no
information was available on this);
- area of land (agricultural and environmental)
affected by landslides and/or flooding (no quantitative
information was available on this);
- costs of emergency repairs to flood defence
structures and number/type of flood events that incur
this expense (no information was available on this
making the estimates highly uncertain);
- length of diversions following landslides/road
closures due to flooding (information was available on
the larger diversions, but not on smaller events which
could result in an under-estimation of total
costs);
- time over which disruption to train services was
experienced, particularly for major lines; and
- social impacts of flooding, some of which may not
become apparent until some time after the flood events.
This will assist in determining whether the non-money
impacts are likely to be small compared to the money
impacts or whether they are larger than predicted.
There are also a number of damage cost estimates that
are based on data for England and/or Wales. It is unclear
whether this damage data provides a good indication of the
costs faced in Scotland, suggesting that some work may be
required to obtain specific cost estimates for Scotland.
The cost estimates used are those that are routinely used
in the assessment of flood defence schemes in Scotland. It
would be possible to compare the figures with those in the
Dundee Flood Loss tables
2 or to check whether the estimates used in this study
are broadly applicable or not.
Environmental costs
Some of these can be quantified in the economic costs,
there are others that are less certain.
SEPA suggest that fluvial water quality
will decrease in a wet year due to disturbance and
increased diffuse run off, while estuarine water quality
may increase due to dilution. The increased categorisation
of water bodies underway as part of the Water Framework
Directive may provide a measure that enables a comparison
of water bodies before and after a flooding event.
Recommendation for further study
The costs indicate that flooding in August contributed a
significant cost to the economy. In addition publication of
this type of report may prompt further information to be
brought forward. Other bodies are still carrying out their
own investigations into the flooding including:
- severity of flooding in Glen Ogle -
SEPA and Universities
- Scottish Water -costs of sewer flooding
- Local authorities in terms of new works
It is likely that the costs and understanding of the
August 2004 event could be refined.
The costs of flooding in August were estimated on the
basis of data collected for this study and in many cases
this inadequacy has been highlighted.
In order to improve and enhance the collection of flood
event data, the key sources of information on flooding are
summarised below Table 6-1 with an indication of the data
type that each body may hold. In establishing accurate cost
for flooding it is necessary to identify the number and
type of properties affected. A number of organisations hold
this information, and in order to develop a clear picture
it is necessary to pool and compare this information. At
present there is not one body with an over arching
responsibility for undertaking this task or with
legislative powers to do so. Some organisations have
expressed concern on data protection issues in terms of
sharing data on properties affected. The information is
also held in a number of forms.
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