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TRANSCRIPT
Dr. Harshinie Karunarathna Engineering from Clouds to Coast Research Group
College of Engineering
Swansea University
Recent Storms and the Coastlines of the UK
Outline
Introduction
Recent storms, coastal erosion and flooding
Impact of frequent storms
Quantifying the impact of frequent storms
FloodMEMORY Project
Wrap up
Introduction
• 2.5 million properties in England and Wales are at risk of river and coastal flooding
• 21000 properties in Scotland are at risk of coastal flooding alone
• A significant proportion of UK coastlines are eroding
• Approximately 700 properties in England are vulnerable to coastal erosion and there will be 2000 more by 2030
• Many coastal communities rely on beaches and sand dunes for defence against coastal erosion and flooding
Recent Storms, Coastal Erosion and Flooding
Recent Storms, Coastal Erosion and Flooding
Swansea Bay dunes before and after 2014 January/February storms
Spring tide level
Dawlish
(Mail Online 06 February 2014)
Recent Storms, Coastal Erosion and Flooding
Recent Storms, Coastal Erosion and Flooding
Dawlish
Waves at Dawlish - January/February 2014 (Channel Coastal Observatory)
Recent Storms, Coastal Erosion and Flooding
Wind speed and direction- January/February 2014 (Swanage Pier) (Channel Coastal Observatory)
Dawlish
Recent Storms, Coastal Erosion and Flooding
Pressure and water levels at Swanage Pier January/February 2014 (Channel Coastal Observatory)
Recent Storms, Coastal Erosion and Flooding
Dawlish - Storm Damage
Wave height and surge – April 2012 (Channel Coastal Observatory)
Impact of frequent storms Waves and surges in Dawlish
Five year monthly averaged wave heights and directions at Dawlish
(Channel Coastal Observatory)
Impact of frequent storms Waves and surges in Dawlish
What happened in Jan/Feb 2014?
Wave heights at Dawlish - January/February 2014 (Channel Coastal Observatory)
Seawall collapse
Impact of frequent storms
Waves and surges are not all….
Frequent storms reduce resilience of beach systems to coastal erosion
and flooding
Quantifying the Effects of Frequent Storms Narrabeen Beach Australia
y = 0.0974x - 173.49
0
10
20
30
40
50
1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001
To
tal
Num
ber
of
sto
rms
Year
Number of annual storm occurrences at Narrabeen Beach
(Karunarathna et al., 2014)
Storm clusters at Narrabeen Beach (Karunarathna et al., 2014)
Definition of a storm cluster at Narrabeen: • Offshore significant wave height of each single storm should exceed 3.0m
and remain higher than 3m for a minimum of 1 hour
• Time interval between consecutive storms in a cluster should be less than 9 days
(Challaghan et al., 2009)
0
2
4
6
8
6/6/88 5/8/88 4/10/88 3/12/88 1/2/89 2/4/89
Hs
max
(m
)
Date
Quantifying the Effects of Frequent Storms Narrabeen Beach Australia
0
2
4
6
8
15/11/94 30/11/94 15/12/94
Hs
(max
) (m
)
Date
TSP = 286
-600
-200
200
600
1000
0 50 100 150
h (
cm)
x (m)
16 11 94
02 01 95
0
2
4
6
8
09/06/84 24/06/84 09/07/84
Hs
(max
) (m
)
Date
TSP = 1567
-600
-200
200
600
1000
0 50 100 150
h (
cm)
x (m)
13 06 84
19 07 84
Storm clusters (left) and corresponding pre-and post-storm beach profiles at Profile 4 (right)
Quantifying the Effects of Frequent Storms Narrabeen Beach Australia
0
40
80
120
160
200
0 2000 4000 6000 8000 10000
Ero
sio
n V
olu
me
(m3/m
)
Storm power (m2hr)
(a)
0
40
80
120
160
200
0 2000 4000 6000 8000 10000
Ero
sio
n v
olu
me
(m3/m
)
Total Storm Power (m2hr)
(b)
Beach erosion volume against storm power for storm clusters.
Beach erosion volume against storm power for single storms
Solid diamonds – measured erosion volume, dotted line – linear trend line
(Karunarathna et al., 2014)
Quantifying the Effects of Frequent Storms Narrabeen Beach Australia
Storm Power 𝑃𝑠 = 𝐻𝑠𝑚𝑎𝑥2 𝐷
Hmax = maximum storm wave height, D = storm duration
FloodMEMORY Project (EPSRC Flood and Coastal Erosion Risk Sandpit)
Aim: To investigate the effects of temporal clustering of flood events on natural, built and socioeconomic systems with memory.
In relation to coastlines, we model impact of temporal clustering of storms and surges and the role of ‘memory’ of coastal systems in reducing
their resilience to erosion and flooding
FloodMEMORY Project
Study Area Sefton Coast Liverpool Bay
FloodMEMORY Project
- Model impact of storm clusters and inter-storm recovery using a combined DELFT3D/SWAN/XBeach modelling system
- Determine storm induced beach erosion, wave overtopping and coastal flooding
FloodMEMORY Project
Model application and comparisons with post-storm beach profiles
(Dissanayake, Brown and Karunarathna, in review)
FloodMEMORY Project
Modelled morphodynamic regime at Sefton Beach (Dissanayake, Brown and Karunarathna - in review)
FloodMEMORY Project
Waves at Liverpool Bay Dec 2013 - February 2014
FloodMEMORY Project
Pressure and wind at Liverpool Bay Dec 2013 - February 2014
FloodMEMORY Project
Tide and Surge at Liverpool Bay Dec 2013 - January 2014
• Combined storm waves and surge is responsible for coastal erosion and flooding
• Frequent storm occurrence weakens natural beaches and man made sea defences thus exposing them into greater risks
• Chronology and interval between storms in a storm cluster can have significant effect on the resilience of a beach to storm attack
• EPSERC funded FloodMEMORY project aims toward quantifying effects of storm clusters on resilience of flood and coastal erosion systems
Wrap Up