Increasing risk of compound flooding from storm surge and rainfall for major US cities
Thomas Wahl1,2*, Shaleen Jain3, Jens Bender2,4, Steven D. Meyers1, Mark E. Luther1
1College of Marine Science, University of South Florida, St. Petersburg, USA.
2Research Centre Siegen, University of Siegen, Siegen, Germany.
3Civil and Environmental Engineering, Climate Change Institute & Mitchell Center for Sustainability
Solutions, University of Maine, USA.
4Research Institute for Water and Environment, University of Siegen, Siegen, Germany.
*Corresponding author. Email: thomas.wahl@uni‐siegen.de
Increasing risk of compound flooding from storm surge and rainfall for major US cities
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NCLIMATE2736
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Supplementary Figure 1 | a–b, Observed data pairs of storm surge (s) and precipitation (p) in real
units. c–d, Comparison of simulated (grey; 1000 events) and observed pairs of ranks. Results are
shown for Chesapeake Bay in Case I (a, c) and Grand Isle in Case II (b, d); the Gumbel copula was used
for the simulations (see Figs. 1b–c).
p (scaled ranks)0.4 0.6 0.8
s (s
cale
d ra
nks)
0.0
0.2
0.4
0.6
0.8
1
p (scaled ranks)0.4 0.6 0.8 1
p (mm)0 50 100 150
s (c
m)
40
60
80
100
120
140
p (mm)0 50 100 150 200 250
1
s (s
cale
d ra
nks)
0.2
0.4
0.6
0.8
1
s (c
m)
40
60
80
100
120
140
20
0
0.2 0.20.0 0.00.0
a b
c d
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SUPPLEMENTARY INFORMATION DOI: 10.1038/NCLIMATE2736
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Supplementary Figure 2 | Case I (a) and Case II (b) τ values for the 30 TGs when precipitation
stations are selected in a 25 km radius (red) and a 50 km radius (blue); grey bars are bootstrapped
standard errors associated with the values derived with the 25 km radius.
−0.2
−0.1
0
0.1
0.2
0.3
0.4
0.5τ
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
−0.2
−0.1
0
0.1
0.2
0.3
0.4
0.5
Tide gauge
a
b
Rank
cor
rela
tion
Kend
all‘s
τRa
nk c
orre
latio
n Ke
ndal
l‘s
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Supplementary Figure 3 | TDCs for a threshold of 0.6 derived from the first (blue) and second (red)
halves of Case I (a) and Case II (b) data sets at sites with at least 55 overlapping years of data
(covering at least 65 years) and at least one significant positive trend in Fig. 2g.
Supplementary Figure 4 | Scatter plots of storm surge (s) and precipitation (p) for NYC in real units;
frames highlight the selected compound and non‐compound events in the same way as in Figs. 3a–b
for Case I (a) and Case II (b).
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
2 5 6 9 10 13 15 16 21 25 26 29 30Tide gauge
Tail
depe
nden
ce c
oeffi
cien
t
a
b
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Tail
depe
nden
ce c
oeffi
cien
t
0 50 100 15050
100
150
200
250
300
p (mm)
s (c
m)
0 50 100 150 2000
50
100
150
200
250
p (mm)
Year
1920
1940
1960
1980
2000
a b
s (c
m)
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Supplementary Figure 5 | Composite plots of PWC (unit is kg m‐1) and wind for events with high
storm surge and high precipitation (a–b; derived from events with circle frames in Figs. 3a–b) and
high storm surge and low precipitation (c–d; derived from events with square frames in Figs. 3a–b);
the NYC TG location is indicated by the red dot. Case I (a, c), Case II (b, d).
Latit
ude
0
20°N
40°N
60°N
20 40
a b
c d
Longitude
120°W 80°W 40°W
Latit
ude
0
20°N
40°N
60°N
Latit
ude
0
20°N
40°N
60°N
Latit
ude
0
20°N
40°N
60°N
Longitude
120°W 80°W 40°W
Longitude
120°W 80°W 40°W
Longitude
120°W 80°W 40°W
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Supplementary Figure 6 | Composite plots of SLP (unit is Pa ∙ 105) (a–b) and PWC (unit is kg m‐1) (c–d)
for events with high storm surge and high precipitation (a, c) and high storm surge and low
precipitation (b, d); the Boston TG location is indicated by the red dot.
1 1.01 1.02
1 1.01 1.02
20 40
20 40
Latit
ude
0
20°N
40°N
60°N
a
c
Latit
ude
0
20°N
40°N
60°N
b
d
Latit
ude
0
20°N
40°N
60°N
Latit
ude
0
20°N
40°N
60°N
Longitude
120°W 80°W 40°W
Longitude
120°W 80°W 40°W
Longitude
120°W 80°W 40°W
Longitude
120°W 80°W 40°W
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