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Weather–November2014,Vol.69,No.11
The hydrological setting
of the 2013 floods in Mexico
Adrián Pedrozo-Acuña,
J. Agustín Breña-Naranjo
and Ramón
Domínguez-Mora
Universidad Nacional Autónoma de
México, Instituto de Ingeniería, Cd.
Universitaria, Coyoacán, México
Introduction
There is increasing evidence that more fre-
quent flooding, resulting from increases
in the frequency and intensity of storms,
is likely to be one consequence of anthro-
pogenic climate change in many parts of
the world (Feng et al., 2013; Kumar, 2013).
In recent years, large-scale floods have
been recorded in Australia, Brazil, Thailand
and the United Kingdom; not to mention
those associated with hurricanes Katrina
and Sandy, which generated combined
economic losses of hundreds of billions of
dollars in the USA (Michel-Kerjan, 2012).
In Mexico, flooding is currently the major
and most costly natural hazard; its geo-
graphical location makes the country highly
vulnerable to the strike of landfalling tropical
cyclones along both the Pacific and Atlantic
coasts. Indeed, this was recently observed
during September 2013, when the simulta-
neous occurrence of two tropical cyclones
affecting both basins of the country was
recorded (see Figure 1). Figure 1 shows the
tracks of both storms as they travelled over
the entire Mexican territory; the star repre-
sents the spatial location of both phenom-
ena at the time at which the picture was
taken. Tropical storm Manuel in the Pacific
and Hurricane Ingrid (category 1) in the Gulf
of Mexico made multiple landfalls between
13 and 20 September. Both systems affected
77% of Mexican territory, with heavy rain-
fall producing landslides and severe flood-
ing along many of the country’s rivers; as
a result, more than 45 000 homes were
damaged or destroyed and 192 lives were
lost (Aon Benfield, 2013). To give a specific
example of one of the recorded impacts:
in the tourist resort of Acapulco-Diamante
the overflowing of La Sabana river left sev-
eral residential and commercial properties
flooded, including the international airport.
Figure 1. Satellite image (NASA Worldview, 2013) taken on 15 September 2013 during the simultaneous occurrence of two tropical cyclones in Mexico,
along with the recorded tracks for Manuel (blue dots) and Ingrid (red dots); stars represents the spatial location of both phenomena at the time the
picture was taken.

296
Weather–November2014,Vol.69,No.11The2013floodsinMexico
Southern Pacific coast of Mexico, where
the tourist resort of Acapulco-Diamante is
located. By contrast, in the Gulf of Mexico,
towards the northeast of the country,
less intense precipitation was observed.
Particularly in this case, high cumulative
precipitation values on the Gulf of Mexico
watersheds are associated with the landfall
position of tropical storm Ingrid.
To further investigate the nature of the
highest registered rainfall during the inci-
dence of this hydrometeorological event,
we examined the weather stations located
in the Southern Pacific region. For this
purpose, we selected the stations that have
at least 30 years of data. These stations are
listed in Table 1, along with the number of
available years of data, the mean annual
precipitation at the station and the corre-
sponding cumulative precipitation recorded
for the period of 1–19 September 2013.
Each station also reported the ratio of the
cumulative precipitation for the event to its
annual mean. It was observed that, by aver-
aging across all stations in the region, the
cumulative precipitation value recorded for
this event was around 52% of the annual
mean value, thus quantifying the extreme
level of precipitation recorded in the region
as a whole. Indeed, for those stations close
to the tourist resort of Acapulco-Diamante,
from weather and gauging stations of
the Mexican Government we estimate the
rainfall return period associated with this
hydrometeorological event. Moreover, we
search for plausible expectations of future
probabilities of extreme floods by estimat-
ing the corresponding return periods of
riverflows at those locations at which large
rainfallreturnperiodswereidentified.Finally,
satellite-derived precipitation products from
the Tropical Rainfall Measurement Mission
(TRMM) (Huffman et al., 2007), are used to
determine, on a month by month basis, how
exceptional the 2013 rainfall was in relation
to previous years (1998–2012).
Precipitation in 2013
The simultaneous occurrence of tropical
storms Ingrid and Manuel provides a cru-
cial setting for the hydrological conditions
observed during September 2013 across
Mexico. Figure 2 shows a map of cumula-
tive rainfall recorded from 1–19 September
2013. The map was constructed using col-
lated data from 1000 rain gauge stations
owned by the National Weather Service
and the Federal Commission of Electricity
(shown as red dots). It reveals that the
most intense precipitation (due to tropical
storm Manuel) was concentrated along the
The incidence of both tropical storms left
anticipated insured losses, as estimated
by the Mexican Association of Insurance
Institutions, in excess of US $900 million,
while economic losses were valued at US
$5.7 billion. As a consequence of current
economic growth (i.e. increased building
on flood plains) and an increase in the fre-
quency and severity of storms, these costs
are set to rise further. It follows that an
improved ability to forecast, quantify and
manage flood risks is essential to protect
the public, property and infrastructure, and
to maintain a sustainable economy. This can
be achieved through the careful identifica-
tion of the causes of an extreme flood, in
combination with a better understanding
of the frequency, intensity and structural
behaviour of such hydrometeorological
events across several aspects of the earth
system sciences. Although the probability of
the simultaneous occurrence of two storms
on both coasts is low, it is necessary to carry
out a careful assessment of the observed
rainfall and river discharges during their
incidence (Figures S1–S3).
In this article we review the hydrological
setting of the 2013 Mexican floods through
examination of the rainfall totals and
anomalies across the whole country. Using
precipitation and riverflow data acquired
Figure 2. Precipitation map for the cumulative rainfall recorded from 1–19 September 2013. Pink dots indicate the locations of weather stations.

297
the ratio of the recorded rainfall in
September with respect to the annual mean
was greater than 70%, with individual ratios
of 75% in Arteaga, 79% in km21 and 79%
in Copala. For clarity, Figure 3 presents the
geographical locations of these stations,
which are colored red or green to identify
those with more than or less than a 40%
ratio of precipitation for the event with
respect to the annual mean, respectively.
It is clear that the majority of the intense
precipitation was located along the south-
ern coast of Guerrero.
The heaviest rain fell over the rain gauge
station known as Huitzuco, with a ratio of
precipitation for the event relative to the
annual mean reported as 186%. This may be
attributed to orographic enhancement due
to the complexity of the terrain.
In order to review the daily precipita-
tion during the event in more detail, three
weather stations with at least 30 years of
historical data were used. Their selection
was determined by their location relative
to the tourist resort of Acapulco-Diamante,
which was heavily flooded on the night of
15 September. They are: Arteaga, km21 and
Copala. Figure 4 shows, for these stations, a
comparison of the historical time series of
daily precipitation (left panels) with respect
to that recorded from the 1–19 September
Table 1
Weather stations in the area of highest precipitation rates during September 2013.
Station State in
Mexico
Years on
the record
Annual mean Rainfall Event Ratio
hp annual
(mm) hp event
(mm) hp event
/hp annual (%)
Caimanera Michoacán 35 974 205 21
Panches Michoacán 34 669 307 46
Pinzanes Michoacán 33 823 172 21
Piedras
Blancas
Michoacán 33 636 193 30
Uruapan Michoacán 33 1487 403 27
Arteaga Michoacán 38 892 673 75
San Cristóbal Guerrero 37 1000 226 23
San Juan
Tetelcingo
Guerrero 34 645 266 41
Huitzuco Guerrero 43 887 1652 186
Acapulco Guerrero 38 1340 782 58
Chilpancingo Guerrero 36 865 397 46
San Marcos Guerrero 45 1269 564 44
La Calera Guerrero 32 953 104 11
El Gallo Guerrero 44 895 86 10
Copala Guerrero 45 1407 1112 79
Ometepec Guerrero 30 1366 826 60
Zihuatanejo Guerrero 34 1027 659 64
Km21 Guerrero 33 1119 885 79
Quetzala Guerrero 41 1239 679 55
Figure 3. Geographical location of rain gauge stations in the Southern Pacific region of Mexico; the catchment of La Sabana river is highlighted
in orange.

298
Figure 4. Historical time series of daily precipitation hp
(left panels) vs. that recorded from 1–19
September 2013 (right panels).
2013 (right panels). The top row of Figure 4
illustrates the comparison for Arteaga sta-
tion, located to the west of Acapulco.
The plot shows that although the station
recorded high values for daily precipitation
during September, they are not above the
recorded historical maxima at this location.
By contrast, the middle row shows results
for the km21 station located closest to
Acapulco. In this case, the registered daily
precipitation is indeed the most exceptional
on record, with more than 400mm recorded
on 15 September. Finally, the bottom row
displays the results for Copala station,
located to the east of Acapulco, for which
the recorded daily rainfall for the period of
analysis is close to the maximum histori-
cal values on record. At all stations, abun-
dant precipitation was recorded between
14 and 16 September 2013, with individual
values as follows: in the region of Arteaga
~400mm, in the central coast of Guerrero (in
Acapulco) ~750mm, and in the eastern part
of Guerrero ~650mm, with highest totals
recorded on 15 September.
These results indicate that the heavy rain-
fall was concentrated in a region close to
Acapulco in the Mexican State of Guerrero.
With rainfall of this magnitude, and daily
precipitation exceeding 200mm within
a period of 2 days, widespread flooding
was inevitable. Indeed, most of the rivers
reported an overflow during the late night
of 15 September 2013, after 1 day of inten-
sive rainfall over the region.
Return period of the
precipitation
The hydrometeorological events recorded
in September 2013 produced record-break-
ing rainfalls across a number of stations on
the southern Pacific coast of Mexico, both
on a daily timescale and for the month of
September. Intense rainfall occurred over
eastern parts of the state of Guerrero,
whereas in the eastern part of the country
the rainfall was somewhat less intense.
In order to review the return periods of the
daily precipitation for this region, an extreme
value analysis based on annual maxima
was carried out for those stations with suf-
ficient historical data and in the proximity
of the Acapulco region. These stations were:
Arteaga (located to the west of Acapulco),
km21 (located at Acapulco), Copala (to the
east of Acapulco) and Huitzuco (to the north).
Figure 5 shows the estimated return periods
for these rain gauge stations. The blue dots
represent the historical annual maxima reg-
istered at each station, while the red stars
show the daily maximum associated with the
September 2013 event.
Figure 5(b) and Figure 5(d) show results for
stations Huitzuco and km21, located close
to Acapulco. Notably, in both cases, the
maximum daily precipitation recorded dur-
ing September 2013 represents an extraor-
dinary rainfall, relative to historical maxima.
Different rainfall patterns are depicted in
Figure 5(a) and Figure 5(c), corresponding
to the results at Arteaga and Copala sta-
tions, which are located to the west and to
the east of Acapulco, respectively. In both
cases, the precipitation associated with the
September 2013 event suggests a return
period of between 25 and 40 years. Figure 5,
therefore, clearly demonstrates a high spa-
tial variability of the return period associ-
ated with this hydrometeorological event.
Precipitation anomaly in 2013
As a complement to the precipitation analy-
sis, we used remotely sensed information
Figure 5. Return periods of daily rainfall
estimated with annual maxima at different
rain gauge stations within the Southern Pacific
region of Mexico (star represents 2013 event).
(a) Arteaga; (b) km21; (c) Copala; (d) Huitzuco.

299
In addition, the monthly variation of the
precipitation anomaly within the TRMM
measurement period (relative to the period
1998–2012) was also estimated for the
whole country and for the Pacific and Gulf
of Mexico regions. Results for the whole
country are reported in Figure 7(a), while
Figure 7(b) and Figure 7(c) illustrate results
for the Gulf of Mexico and Pacific regions,
respectively. It is clear that the precipitation
anomaly associated with September 2013
is indeed the second largest anomaly on
record for the three cases.
To further examine the temporal variability
of the TRMM derived rainfall, Figure 8 shows
the monthly average rainfall on a year-by-
year basis (blue lines) from 1998 to 2013,
spatially averaged for the whole country. The
monthly ensemble average precipitation is
also shown in dark red, spanning the stand-
ard deviation in light red (±σ). The results
indicate that one of the largest monthly
average precipitation measurements in the
last 15 years of observations in Mexico was
indeed recorded in September 2013.
Streamflow return period
Due to the exceptional nature of this
event, and given the impacts observed in
several cities of southern Mexico, especially
tive precipitation for the period 1999–2013.
The results are shown in Figure 6, where a
positive precipitation anomaly (relative to
the period 1998–2012) is identified in those
areas of the country in which the tropical
storms made their landfall. In particular, a
marked rise in precipitation is evident on
the Pacific coast.
as recorded by TRMM to estimate the reg-
istered precipitation anomaly in Mexico
for the year 2013, with respect to the total
measurement period of TRMM (1998–2012).
At each TRMM cell within the country
(25 × 25km), this anomaly was determined
by subtracting the recorded cumulative pre-
cipitation for 2013 from the average cumula-
Figure 6. 2013 annual precipitation anomaly (mm) in Mexico (relative to period 1998–2012).
Figure 7. Monthly variation of the precipitation anomaly in (a) Mexico (b) Atlantic region and (c) Pacific region, within the TRMM measurement period
(cf. 1998–2012).

300
occurrence of the peak flows. It is clear that
the estimated value for the peak flow during
the 2013 event is of the order of magnitude
of other maximum values observed at this
gauging station. Horizontal lines represent
the different return periods estimated from
the analysis, showing that the 2013 event cor-
responds to a return period ranging between
1 in 20 years and 1 in 50 years for this river.
The Acapulco flood
The results presented above show that the
precipitation observed at the Pacific coast
of Mexico in September 2013 was generally
associated with spatially-varied return peri-
ods of 25–70 years. Although these return
periods do not represent a low probabil-
as km21, where historical information on
the magnitude of the river discharge is
available. The Sabana River has a catchment
of 1074.4km2
with a concentration time of
6h, and the best estimate of discharge was
of the order of 1000–1300m3
s−1
.
A first-order estimation of the return
period for this event was established with
the support of an extreme value analysis
using historical data from a gauging sta-
tion located at the Sabana river watershed;
the measurements were available at daily
intervals for a period of 45 years from 1958
to 2003 (Figures S4–S6).
Figure 9 shows the time series of daily
streamflow measurements from January
1958 to January 2003. The seasonal varia-
tion in total discharge is evident from the
in Acapulco-Diamante, a post-flood sur-
vey was carried out by members of the
Hydraulic Department of the Institute of
Engineering at the National University of
Mexico. This activity involved the iden-
tification of watermarks in the region in
order to reconstruct the peak flow value
for the event. The flood peak discharge
was estimated from a stage-discharge rela-
tion, which is anchored at high discharges
by indirect discharge measurements. This
stage-discharge curve was applied to a
point of the river upstream of the zone of
the overflow. This estimate was carried out
following recommendations put forward
by Lumbroso and Gaume (2012). The loca-
tion at which the procedure was applied
corresponds to the gauging station known
Figure 8. Deconstruction of a monthly TRMM rainfall (hp) series on a year by year basis.
Figure 9. Time series of daily streamflow (Qinst
) at km21 station from January 1958 to January 2003. Horizontal lines represent the different return periods (Tr).

301
the impacts were destructive due to the
combination of an intense rainfall and the
vulnerability of man-made structures built
within flood-prone areas, thus showing
that economic change has had a profound
influence on the impacts of flooding in the
region, considerably increasing the risk.
In Mexico, this highlights the urgent need
for holistic approaches to flood risk manage-
ment, instead of the current focus on emer-
gency response and recovery. In particular,
this event points towards the necessity
for vulnerability monitoring. It is apparent
that, through the detection of changes in
exposure within floodplains and wetlands,
a disaster could be identified before it hap-
pens. This could be achieved through the
implementation of an adaptive approach to
flood risk reduction, as has been observed
in the Netherlands (Van Alphen, 2013) and
the United Kingdom (Hall and Solomatine,
2008), where coordination of planning and
decision making is key in the design of a
successful flood risk management strategy.
Summary
Recent events in Mexico and around the
world indicate that better communication
between researchers, decision makers and
society is pivotal for the generation of a
successful disaster risk reduction strategy.
ity for the event, it is very likely that the
2013 floods will rank as one of the coun-
try’s most damaging hydrometeorological
events to date. This may be ascribed to the
spatial coverage of intense precipitation
over a large area of the Mexican territory,
in contrast to a generalised low probability
of the precipitation itself.
In particular, the well-known coastal
resort of Acapulco-Diamante was heavily
damaged by flooding; the intense precipi-
tation recorded (~650mm/48h) gave rise to
extreme flood discharges in La Sabana river.
The impact of this flooding on property and
infrastructure was severe, widespread and,
in some cases, long-lasting. Figure 10 shows
a true color (RGB) version of the satellite
image of this region taken on 18 September
2013, and shows that by that date, after
the passage of the peak discharge, flood-
ing was severely affecting urban develop-
ments and hotels. In this image, floodwaters
are illustrated by the brown/pink colours
that visually represent the large amount of
sediment that was transported during the
event. Figure S7 shows an infrared version
of the same scene, where dark blue regions
illustrate floodwaters, red areas represent
vegetation, and white areas indicate the
presence of urban developments.
The severity of flooding is a consequence
of a combination of conditions; in this case,
Figure 10. Satellite image of the flooded area, recorded at Acapulco-Diamante on 18 September 2013.
Moreover, the size of registered damages
and losses reveals the urgency of doing so,
evenunderacontextoflimitedpredictability.
In the case of the hydrometeorological
eventrecordedinSeptember2013inMexico,
a consensus of different estimates suggests
a return period ranging from 20–50 years.
Recorded rainfall totals for September 2013
exceeded records by, on average, 52% of the
annual mean at several rain gauge stations,
with extraordinary cases reaching up to 70%
of the annual mean in 2 days. However, it
should be noted that the estimates may be
biased low owing to the limited 30–50 year
extent of the historical data used.
In view of the magnitude and ubiquity
of the hydro-climatic change now under
way, understanding the complexities of
the interrelationships of natural and social
domains is vital. There is ongoing work to
model the flooding that occurs as a result
of these hydrometeorological events, with
some success in recent times due to greater
model capability and access to high qual-
ity precipitation and topographic data (e.g.
LiDAR). Although results from models have
a certain level of uncertainty, a probabilistic
methodology is being developed in order
to produce an improved flood modelling
approach (Pedrozo-Acuña et al., 2013).
Although it is meteorological trends that
are important in the evaluation of global cli-
mate change, attention should also be paid
to vulnerability monitoring and its interac-
tion with extreme precipitation events that
result in disastrous floods. This analysis is
therefore important to those responsible for
flood control in their efforts to adopt effec-
tive preventive measures and to mitigate
the impact of the floods that do occur.
Acknowledgements
This paper was written with the support of
the Institute of Engineering, UNAM, through
an internal project. The authors would like
to thank the colleagues that participated in
the field campaign carried out in October
2013 at Acapulco-Diamante: Antonio
Capella Vizcaino, Judith Ramos Hernández,
José Luis Herrera and Iskra Mejía Estrada.
Miguel A. Laverde-Barajas and Juan P.
Rodríguez-Rincon are gratefully acknowl-
edged for their help with figure editing.
References
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Hall JW, Solomatine D. 2008. A frame-
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302
Figure S2. Flood impacts in recent urban
developments along the banks of La Sabana
River, Acapulco Diamante.
Figure S3. Overflow of La Sabana river
(flow is from left to right in the image).
Figure S4. Bank scouring erosion at
Chilpancingo city, Guerrero.
Figure S5. Impacts to urban infrastructure due
to bank scouring at Chilpancingo city, Guerrero.
Figure S6. Large flow velocities observed
at Río Huacapa, Chilpancingo, Guerrero.
Figure S7. Infrared satellite image of the 2013
flood in Acapulco-Diamante, Mexico.
Supporting information
The following material is available as part of
the online article.
Figure S1. Aerial overview of the flood impacts
registered in Acapulco Diamante, Guerrero,
due to the overflowing of La Sabana river
(September 2013).
Correspondence to: Adrián Pedrozo-Acuña
APedrozoA@ii.unam.mx
© 2014 Royal Meteorological Society
doi:10.1002/wea.2355
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is your country? Nature 491: 497.
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gov/1eTbpqi (accessed 17 July 2014).
Pedrozo-Acuña A, Rodríguez-Rincón JP,
Arganis-Juárez M et al. 2013. Estimation
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The weather of 2013
Helen Roberts
Met Office, Exeter
2013 was another year of interesting
weather, with extremes and records being
broken across the globe. This article follows
on from the Royal Meteorological Society
conference in February 2014: Understanding
the Weather of 2013.
January
The year stared with the coldest weather
in northern India for 44 years, with the
lowest maximum temperature on record
for New Delhi at 9.8°C. The remnants of
ex-cyclone Oswald made landfall in north-
ern Queensland, bringing extreme rainfall
and power outages. Meanwhile, it was the
hottest January on record for Australia as a
whole, with both average mean and aver-
age maximum temperatures exceeding
previous records (Bureau of Meteorology,
2014), resulting in large numbers of wild-
fires across the country. January also saw
one of Beijing’s worst spells of air pollution,
causing aviation problems and health con-
cerns. Lebanon had some rare snow, nearly
1.5m in some northern parts of the country,
with temperatures more than 5 degC below
normal. Closer to home, there was plenty of
snow for much of the United Kingdom too
in flooding in Angola. Meanwhile, back in
the United Kingdom it was still very cold,
with the coldest Easter Sunday on record at
−12.5°C overnight in Braemar, and the snow
continued as well, killing more than 20 000
sheep. It was not just the United Kingdom
shivering though, as Spain also saw some
unusual spring-time snow.
Figure 1. Snow covering much of the UK on
26 January 2013. (Image credit: NEODAAS/
University of Dundee.)
(Figure 1), with blizzards in some northern
areas.
February
In February, Australia confirmed their sum-
mer as the hottest on record and it was
locally named ‘The Angry Summer’. Saidu
Sharif in northern Pakistan experienced
nearly double the average monthly rainfall
in just 48h, and a powerful northeaster in
the USA, named Winter Storm Nemo, pro-
duced the all-time greatest snowstorm for
Portland (Maine) with 81cm.
March
In March, Mississippi sheltered from hail
the size of baseballs. Meanwhile, Virginia
declared a state of emergency after severe
blizzards hit the US east coast. The USA was
not the only place to experience blizzards
though, with parts of northern Japan buried
under feet of snow as well. It was rain rather
than snow causing problems in Mauritius,
with a day of national mourning after 11
people died in severe floods.
April
April saw some torrential rain of its own,
with deadly flash flooding in Argentina,
when La Plata had 400mm of rainfall in
just 2h. Yet more torrential rain also resulted

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