Transcript Flooding Changes around the Firth

Flooding:
Changes Around the Firth
Mark McLaughlin
Senior Hydrologist (Flood Map Manager)
Scottish Environment Protection Agency
Firth of Clyde Forum - 11 November 2008
Content
 Flood events around the Firth
 Climate change and the potential impacts
 SEPA’s role
• Flood Risk
• Mapping: Indicative River & Coastal Flood Map
(Scotland)
- Future development
• Flood Warning
 Future changes – European Directive on Assessment
and Management of Flood Risks
 Conclusions
Recent Flood Events Around the
Firth of Clyde
 January 1991 – result of a significant tidal
surge
• Flooding along the Ayrshire coast
(Saltcoats)
• Highest observed levels at Greenock,
Tarbert, Saltcoats, Millport & Rothesay
 January 1993 – tidal surge
 Significant surge levels in October 2008
(+1m) – no flooding though
Flood Events in the Firth of Clyde –
Stevenston/Saltcoats
Flood Events in the Firth of Clyde –
Helensburgh
Flood Events in Loch Fyne – Tarbert
Potential Impacts of Future
Climate Change
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More variation in weather patterns
Increased storminess
Increase in sea level
Increasing frequency of significant surge
events
 Increased rainfall/fluvial flooding (summer too)
Climate change and flooding –
UKCIP02 predictions
 20% increase in river flows by 2080
 1% probability event becomes a 2% event by
2080
 30cm increase in mean sea level by 2080
 Increased storminess - wave and storm
surges
 Daily mean temperature increase 4oC by
2080
Percentage Change in Wave Height
(winter periods 1985-89 and 1991-96)
Days of Heavy Rain - >10mm/day
(Change 1961 – 2004)
Changing River Flows
70
20
60
18
16
50
40
30
20
Winter
5 per. Mov. Avg. (Winter)
Linear (Winter)
10
Flow (cumecs)
0
14
12
10
8
6
Winter
5 per. Mov. Avg. (Winter)
Linear (Winter)
4
2
45
Annual winter flow
5 year moving average
Linear (Annual winter flow)
40
35
30
25
350
300
Flow (cumecs)
50
R.Teith at Bridge of Teith winter
flows (Oct-Mar),1957-1996.
R.Tay at Ballathie winter
flows (Oct-Mar),1958-1996
Annual winter flow
5 year moving average
Linear (Annual winter flow)
250
200
150
20
15
1957 1961 1965 1969 1973 1977 1981 1985 1989 1993
100
1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994
2000
1997
1994
1991
1988
1985
1982
1979
1976
1973
1970
1967
1964
1961
1958
1955
19
58
19
61
19
64
19
67
19
70
19
73
19
76
19
79
19
82
19
85
19
88
19
91
19
94
19
97
20
00
1949
0
55
Flow (cumecs)
Winter Flows, R Kelvin
at Killermont, 1949-2000
1952
Flow (cumecs)
Winter Flows - River Nith
at Friars Carse 1958-2000
Impacts of Climate Change
• Economic
• Social
• Environmental
SEPA’s Role in Managing Flood
Risk
Currently:
 Planning
• Advice
• Mapping
 Flood Warning
• Schemes (rivers and coastal)
In the (very near) future:
 European Directive on the Assessment and
Management of Flood Risks
SEPA’s Role – Flood Risk
Section 25 of Environment Act requires that SEPA provides
Local Planning Authorities, upon request, with advice on the
risk of flooding based on the information which it holds.
Town & Country Planning Act - SEPA is a statutory consultee
on developments at flood risk
Development of a Flood Map for Scotland
•
To support our role as a statutory consultee
•
To support planning policy and guidance
•
To raise public awareness
Borders 1977
Why do we need flood maps ?
Maps are the most effective way
of communicating information on
flood risk at a local, regional and
national level to planners,
developers and residents.
Development of the
Indicative River & Coastal Flood Map
(Scotland)
Summary of the Flood Map project:
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Funded by Scottish Executive - £1.3m
Contract awarded in 2004
Completed 2006
Public Launch on SEPA web site November
2006
Indicative River & Coastal Flood Map
(Scotland)
 To map 3 extreme flood
events (100yr, 200yr and
1000yr) in rivers and coastlines
around Scotland
 Utilised industry standard,
generic methodologies
 Utilised automated processes
to allow large amounts of
modelling to be done in a short
time
 Supplemented by detailed
model outputs where available
Creating the Maps
Fluvial Maps
Key datasets and methodologies have recently become
available which now allows us to use computer models to
amalgamate the data and allow us to generate a national
flood map cost effectively.
The NEXT MAP
digital terrain
model is a
detailed high
resolution map
of Scotland
Creating the Maps
Estimates of 100yr, 200yr and 1000 year flood flows at
every 50m grid point along 25,000km of river was used to
generate a water depth in the floodplain.
For the fluvial flood maps, the data was imported into
hydraulic modelling software linked to a GIS framework
Creating the Maps
Creating the Maps
Coastal Maps
Coastal flood outlines created using Proudman
Oceanographic Laboratory (POL) extreme sea level method
and projected inland over the Digital Terrain model
Coastal Flood Map - Projection Method
0.1% Design Water level
0.5 % Design Water level
1% Design Water level
DTM surface
Creating the Maps
Limitations of the Flood Map
 No specific consideration of flood defences
 No inclusion of hydraulic structures
 No specific inclusion of other types of
flooding
 Limitations of the methodology
 The Flood Map provides a strategic level of
information and is not suitable for individual
property assessment, but is a flood
management tool to support development
planning.
Future Map Development
 Improved topographic information (LiDAR)
• Particularly for urban areas
 Refinement of the estimation of the extreme
design flows
 Improved modelling (calibration against
recorded events)
 Coastal development
• Improved representation of bathymetry,
especially for sea lochs
 Development of Flood Risk & Hazard Maps in
line with current European Directives
SEPA’s Role - Flood Warning
 SEPA is the Flood Warning Authority in
Scotland (Environment Act 1995)
 FW relies on effective partnerships
 SEPA provide a 24/7 flood warning service.
 Hydrologists monitor flood events and issue
warnings to the public via the police, local
authorities and ‘Floodline’.
 Hydrologists maintain communication with
LA’s, emergency services and the Hydroelectric companies throughout the year.
SEPA’s coastal flood warning
strategy
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SEPA has developed a coastal flood warning
strategy
Includes a vision for a nationally integrated
flood warning service for coastal
communities
Has two phases:
1. A flood watch service for broad coastal
areas covering the entire Scottish coast
2. A flood warning service for specific at-risk
communities
The strategy is supported by the Scottish
Government
Key elements of the strategy
 Improving our understanding of risk
 Improving our understanding of coastal processes
 Identifying the resources required
 Working with partners
 Seeking funding
 Integrating with existing flood warning schemes – Firth
of Clyde
Coastal Flood Watch for Scotland
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Live February 2007
Uses alerts from the Met Office
Based on 9 Coastal Zones
28 forecast points
Issued through Floodline
Local Authorities/Police informed of flood
watch
Storm Tide Forecast Service
Forecast
points
CS 3 model
European ‘Floods’ Directive
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Directive 2007/60/EC on the Assessment
and Management of Flood Risks
Objective: ‘the establishment of a framework
for measures to reduce the risks of flood
damage’
Currently being transposed into Scots Law
European ‘Floods’ Directive
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Identification of Competent and Responsible
authorities
Scale – river basin districts
Three elements:
1. Preliminary Flood Risk Assessment by
December 2011
2. Development of Flood Hazard & Risk
Maps by December 2013
3. Flood Risk Management Plans by
December 2015
European ‘Floods’ Directive
 Recognises that floods are natural
phenomena which cannot be prevented but
that some human activities (including
increasing development on floodplains) and
climate change contribute to an increase in
the likelihood and adverse impacts of flood
events
 Integrated approach to managing flood risk on
river basin and sub-basin scale
 There are therefore clear links with SEPA’s
duties on Flood Risk and Flood Warning in
overall flood risk management
Conclusions
 With respect to flooding, there is a potential
for significant changes in the area of the Firth
of Clyde.
 Physical – potential increased risk as a result
of climate change
 Legislative – integrated approach to flood risk
management as a result of European
directions and Scots Law