NHESSNatural Hazards and Earth System SciencesNHESSNat. Hazards Earth Syst. Sci.1684-9981Copernicus PublicationsGöttingen, Germany10.5194/nhess-18-2027-2018Identification and classification of urban micro-vulnerabilities in tsunami evacuation routes for the city of Iquique, ChileUrban micro-vulnerabilities in tsunami evacuationÁlvarezGonzaloQuirozMarcohttps://orcid.org/0000-0003-2548-6265LeónJorgeCienfuegosRodrigoracienfu@ing.puc.clhttps://orcid.org/0000-0001-5768-2477Departamento de Ingeniería Hidráulica y Ambiental, Pontificia Universidad Católica de Chile, Santiago 7820436, ChileDepartamento de Arquitectura, Universidad Técnica Federico Santa María, Valparaíso 2390123, ChileCentro de Investigación para la Gestión Integrada del Riesgo de Desastres (CIGIDEN), CONICYT/FONDAP/15110017, Santiago 7820436, ChileRodrigo Cienfuegos (racienfu@ing.puc.cl)26July20181872027203928December201718January20182June201829June2018This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/This article is available from https://nhess.copernicus.org/articles/18/2027/2018/nhess-18-2027-2018.htmlThe full text article is available as a PDF file from https://nhess.copernicus.org/articles/18/2027/2018/nhess-18-2027-2018.pdf
Many coastal cities around the world are threatened by tsunamis;
some of these events have caused great impacts in recent times. The loss of
human lives during these events is the main cause of concern of the
authorities, and evacuation planning has been recognized as one of the best
tools for safeguarding the population. In this context, urban design appears
to be critical for the execution of prompt and efficient evacuation processes
to safe areas; however, evacuation assessment has been traditionally carried
out at a large urban scale, mostly taking into consideration urban morphology
and connectivity. In the present work, urban spaces available for tsunami
evacuation are explored in detail by developing a methodology to identify and
classify urban micro-vulnerabilities that may reduce the capacity of the
evacuation routes and hinder evacuees' safety. The method is applied to the
Chilean city of Iquique, affected by an earthquake and subsequent tsunami in
2014.
Introduction
Most of the world's commercial activity takes place in port cities, which are
important areas of resources exchange, tourism, and recreation. Coastal cities
have undergone major urban and population growth in recent decades, a trend
that is expected to continue in the future . Coastal growth
increases the exposure of people and property to natural hazards and thus has
a negative consequence on the risk level of urban settlements
.
Tsunamis are one of the most challenging coastal threats for communities
located in subduction zones where the rapid arrival of tsunami waves can
produce significant damage and loss of lives once they reach the coast.
Tsunami risk is determined by combining the probability of being reached by
these waves, the degree of exposure, and the vulnerability of the population
and the physical infrastructure. Mitigation of tsunami risks in coastal
cities requires the evaluation of each of these dimensions (hazard, exposure,
and vulnerability) , while improving their resilience requires
additionally to evaluate their capacity to absorb disturbances, reorganize,
and adapt, keeping its principal functions in operation .
Recent experiences and a better understanding of the tsunami hydrodynamics
have enhanced our ability to mitigate the consequences derived from this
natural hazard. This knowledge has led to the design of countermeasures,
which may be cataloged as structural and non-structural. The former are
long-term countermeasures such as relocation to elevated zones and the
construction of large civil engineering defences (i.e., sea walls,
breakwaters, or sea gates) which are conceived to reduce the energy of
tsunami waves prior to reaching populated areas. Among the non-structural
countermeasures, early warning systems, evacuation planning, and rapid
assistance in response to disasters are considered a priority to reduce the
potential impacts of tsunamis. In addition, other countermeasures have been
recognized, such as urban planning, building codes, and recovery plans
.
The 2011 Tōhoku tsunami showed that structural countermeasures can
be insufficient, due to design and historical data limitations, as the
magnitude of the tsunamigenic earthquake and the height of the tsunami can be
greater than expected. However, such countermeasures can help in reducing the
impact of the tsunami waves in terms of their heights and arrival times at
the coast . Global experiences have demonstrated that the
most effective method of saving lives against tsunamis is a prompt evacuation
. Therefore, the implementation of warning systems and
evacuation preparedness are very important as the combination of different
types of countermeasures is crucial in reducing the losses caused by
large-magnitude tsunamis . In this regard, it has been
recognized that it is important to promote constant investment in education,
planning, monitoring, and improvements of the urban infrastructure
. This is especially important in developing countries,
where the use of large structural countermeasures is uncommon due to their
high costs and slow implementation times.
Essential information for a better preparedness in case of future disasters
can be obtained from post-tsunami surveys where maximum run-up levels and
inland inundation are determined . Chile is among the countries
with the longest history of tsunamigenic earthquakes. Indeed, three
destructive tsunamis have hit the Chilean coast since 2010. In 2010 Chile
faced the most deadly tsunami in Latin America in recent decades, with a
death toll of 156 and 25 missing people , and a maximum run-up
that reached 29 m in the city of Constitución . In 2014, the
8.2 Mw Pisagua earthquake took place in northern Chile and produced a
tsunami with a maximum run-up of 4.63 m recorded in Caleta Camarones, but no
casualties were attributed to it . In 2015, the 8.3 Mw Illapel
earthquake shook north-central Chile with an ensuing tsunami whose maximum
run-up reached 13.6 m in La Cebada, causing 15 fatalities in total
.
Some structural countermeasures were implemented in the most affected zones
in the aftermath of the 2010 tsunami, specifically in the coastal area of the
Bío-Bío Region, including promenades, low sea walls, and, to a greater
extent, relocation of populated areas to higher elevations .
However, these measures are not necessarily representative of the tsunami
mitigation strategy adopted at the national level. In the Chilean case, most
of the efforts have been aimed at fostering tsunami risk awareness through
education, evacuation drills, and installation of signage along escape
routes.
The present study aims at developing a sound methodology to identify and
classify potential “micro-vulnerabilities” in the urban space that may
difficult pedestrian evacuation processes. Specifically, the analysis is
focused on the physical aspects of the built environment that can contribute
to urban vulnerability, in particular in the case of tsunamis and their
related evacuation processes. The criteria used for the identification of
these aspects are based on the literature, where the positive or negative
influence of physical characteristics of indoor and outdoor spaces on the
safety of people against tsunamis and other hazards is examined
e.g.,. We develop and apply a methodology
to assess the micro-vulnerabilities that may reduce the capacity of
evacuation routes in the city of Iquique, located in northern Chile. This
city is susceptible to large-magnitude earthquakes and their ensuing
tsunamis and currently exhibits significant urban vulnerability problems for
evacuation .
This article is structured in the following manner. First, a theoretical
background is provided about the role of appropriate urban forms in
mitigating tsunami-related vulnerability. Second, the study area in Iquique,
along with its coping strategies to mitigate the tsunami hazard, is
described. Third, the method for quantifying micro-vulnerabilities is
detailed in order to subsequently present the obtained results. Finally, the
possible consequences of the existence of micro-vulnerabilities on evacuation
routes and the measures proposed to decrease tsunami risk in coastal cities
are discussed.
Gaps in tsunami evacuation planning: linking urban macro- and microscales
Post-disaster reconstruction is an opportunity to use urban design in view of
obtaining a more resilient city without neglecting economic development and
the quality of life of the affected populations .
The need to implement measures in a short time in order to guarantee the
wellbeing of those affected is the source of a large part of the measures and
studies that focus on reconstruction and the development of post-disaster
recovery plans . However, only a few
of these address the rethinking of the cities' urban design .
describes the historical evolution of landscape planning aimed
at mitigating the risk of urban fires (as the result of large earthquakes);
she underlines the role of open spaces (e.g., parks and streets) and the
improvement of river banks to guarantee water access as planning actions to
achieve a safer city. analyze post-earthquake reconstruction,
showing how an appropriate arrangement of public spaces and design of a
network of open spaces and evacuation routes allows changing the urban form from a dense spatial structure to one that is more attractive, safe, and
resilient to disasters. The works of emphasize the
importance of urban design, especially the road network and public spaces, in
evacuation, the search for shelter, and access to basic and emergency services
in the event of a tsunami. Similarly, suggests that a design
that considers the capacity and accessibility of the road network and the
presence of evacuation routes can decrease urban vulnerability and have a
significant impact on the behavior and attitude of individuals in the face
of large seismic events.
Urban planning has the potential to facilitate the emergency response of
coastal communities against tsunamis when geophysical knowledge is properly
integrated. Planning can have positive effects throughout all the stages of
emergency management in case of an earthquake and tsunami event. During the
catastrophe it can provide safe routes for evacuation and sheltering of
evacuees and allowing emergency services to reach in-need populations, thus
allowing the city to rapidly begin recovery processes . Good
management of the urban form can reduce vulnerability and accentuate
resilient characteristics in a city by creating better conditions for coping
with alterations caused by events such as earthquakes and floods. To achieve
resilience in cities, it is necessary to generate redundancy degrees, which
can be accomplished through increased spatial and functional diversity, and
spatial integration of the ecosystem into urban planning .
Proper urban design not only enhances urban preparedness and safety, but also
promotes city development and tourism growth through a better use and
improvement of public spaces .
(a) Geographical location of the study area and a
selection of major earthquakes (red circles) that have affected north-central
Chile since 1868 (epicenters based on the records of the National
Seismological Center of the University of Chile and the United States
Geological Survey). (b) Downtown Iquique and its tsunami
evacuation routes (modified from ). (c) The Iquique
tide gauge tsunami signal for the 2014 event; the red star indicates the
moment of earthquake occurrence.
Most of the aforementioned studies focus on proper urban management on the
macroscale of urban configuration, i.e., the system of connected spatial
elements that should be available to foster a prompt evacuation of the
community at risk , mainly through modifications in road
connections, creation of open spaces, and guaranteeing the access to shelters
and availability of basic services. report on a gap in the
literature regarding risk reduction; they suggest that it is also necessary
to carry out analysis from a microscale perspective, i.e., at the pedestrian
experience level, of the public spaces available for evacuation and access to
safe areas in case of events such as tsunamis. In addition,
mention the importance of evaluating the susceptibility and reliability of
evacuation routes with a detailed focus. In the light of the exposed
literature, microscale urban vulnerabilities assessment and the
identification of their potential negative impacts in evacuation processes is
largely justified.
Tsunami hazard in Iquique
The Chile–Peru subduction zone, between the Nazca and South American plates,
has an extremely high seismic activity, producing large earthquakes
(Mw> 8) about every 10 years ; some of greater magnitude
have triggered tsunamis, causing loss of human life and substantial
infrastructure damage . Three large earthquakes have
occurred between years 2010 and 2015 in the Chilean territory: the 27
February 2010 Mw 8.8 Maule earthquake , the 1 April 2014
Mw 8.2 Pisagua earthquake , and the 16 September 2015
Mw 8.3 Illapel earthquake . They triggered tsunami waves
that resulted in great damage to ports, coastal cities, and fishermen's
coves.
Despite the magnitude of these earthquakes and their resulting tsunamis, the
death tolls were low in comparison to lower-magnitude events such as the 2010
Mw 7.7 Mentawai Islands earthquake and tsunami with a death toll around
500 people . The relative low number of casualties in Chile has
been attributed to the fast self-evacuation culture promoted among the local
coastal residents, demonstrating the importance of education and awareness
programs . Nevertheless, to develop a safe self-evacuation
process, the urban environment has to be well designed and maintained to
provide an appropriate support.
The Norte Grande region in Chile (an area around 1000 km long,
from the Arica Region to the south of the Antofagasta Region; Fig. )
has been the source of constant public and scientific
concern due to the existence of a seismic gap that has produced an
accumulation of elastic deformation (6–7 cm yr-1) of high seismic
hazard . The last reported destructive tsunamis in this
area occurred in 1868 (Mw∼ 8.8), 1877 (Mw∼ 8.8), and 2014 (Mw 8.2)
. Lower-magnitude earthquakes have also occurred in this
area, such as the 1967 Mw 7.4 and the 2007 Mw 7.7 events near the city of
Tocopilla; however, a large part of the shallow subduction zone did not
experience ruptures for a long period . Indeed, the release of
energy in 2014 proved to be less than expected, amounting to only around 20 %
of the total accumulated energy since the 1877 earthquake . This suggests the possibility that a larger-magnitude event could
occur in the future, the epicenter of which could be located either south or
north of Iquique .
The city of Iquique is located in the center of this seismic gap area
(20.53∘ S, 70.18∘ W). Iquique's territory is a narrow coastal
strip no wider than 3 km with a constant upward slope toward the east, where
it is surrounded by a mountain system. Iquique is an important port and
center of activity for the country's mining industry, with a population of
184 953 according to the last census . It plays an essential
role in the transport of goods to nearby countries, supported by a growing
duty-free zone (which has also led to a boom in the city's car market and the
subsequent high traffic levels).
Tsunami hazard has not been adequately recognized in the urban development of
Chilean cities. Only after the 2010 tsunami did the government amend the
ordinance of urbanism and construction by defining restricted areas to urban
development in tsunami flood zones , but there is still lack
of national policies to mitigate the impact of tsunamis .
Fortunately, as shown in Fig. , Iquique has adequate urban
morphological characteristics (on a macro level) for carrying out a fast
evacuation, thanks to the orthogonal arrangement of its streets
. This is a common factor in Latin American cities, which in
coastal areas might lead to straight and redundant evacuation route layouts
.
The 2014 earthquake triggered a moderate tsunami that resulted in minor
flooding of the Iquique coast and nearby fishing villages, mostly damaging
boats and small docks; no destruction of dwellings was reported and most
damage was a result of the earthquake . In interviews done
by , one of the stressed points was the importance of the drills
conducted prior to the tsunami, which proved to be effective for identifying
safe places and the closest evacuation routes at the time of the event. A
large part of the population started a prompt evacuation after the end of
seismic shake and demonstrated a good understanding of tsunami warning issued
by authorities , which are proof of the ongoing evacuation
education policies in the country. However, a range of problems were
identified during the emergency, including the use of cars (which led to
accidents and street blockages) and the lack of street lighting due to the
massive power failure caused by the earthquake .
Summary of the proposed methodology to identify and classify urban
micro-vulnerabilities.
Records from the Iquique tide gauge (Fig. ) indicate that the
first tsunami wave reached the coast at 20:56 LT (local time), 9 min from
the nucleation of the earthquake; the first peak, with a height of 1.6 m,
was recorded at 21:06, only 19 min after the initiation of the
seismic shaking . In addition, arrival times for the 2015
Illapel tsunami were found to be less than 12 min in the field survey
conducted by . This demonstrates that, depending on the location
of the tsunami generation area, little time may be available for evacuating
to safe areas; therefore, a rapid response and evacuation are essential as
protective measures against near-field tsunamis in Chilean coastal cities.
Material and methods
Public spaces (especially escape routes) play a critical role in the case of
near-field tsunamis by fostering the evacuation of pedestrians to safe
areas. Ideally, these spaces should remain clear and free of obstacles in
order to guarantee that the design capacity of the route is not altered
. In the fieldwork carried out by , a series of
vulnerable points on a microscale level were detected on evacuation routes
in Iquique, which were classified (according to their origin) into three
categories: (i) precarious physical conditions and inadequate maintenance,
(ii) problems related to the design of the public space, and (iii) inappropriate
use of sidewalks. Larger surveys should focus on a
quantitative analysis at this scale.
Following the prior guidelines and as a complement to the more qualitative
approach developed by , we conduct here a detailed microscale
analysis of the Iquique's urban context in an attempt to characterize
potential difficulties of carrying out effective evacuation processes. The
central part of Iquique (see Fig. ) is an urban area
characterized by a high population density and traffic flow, along with
intensive commercial, touristic, industrial, and educational activity; these
factors contribute to a high exposure to tsunami hazard and motivate the
development of the proposed methodology.
Our work was developed following sequential trajectories
of analysis along the evacuation routes proposed by the
municipality of Iquique in conjunction with the National Emergency Office in
its plan for civil protection against tsunamis . These routes
were defined as the shortest paths, oriented from west to east from the
coastline that lead to high ground areas (30 m a.s.l.). The
methods used in this study comprise three steps. First, extensive fieldwork
is conducted to perform a diagnosis of evacuation routes, following the path
of evacuees during their escape. Next, surveyed micro-vulnerabilities are
geo-referenced and classified according to their complexity and consequences
in evacuation, and, finally, a friction rate that accounts for velocity
reductions of pedestrians is proposed based on the literature review. A
summary of the methodology that is described in detail in the following
subsections is presented in Fig. .
Identification of micro-vulnerabilities along evacuation routes
During October 2015, a detailed diagnosis of the current state of evacuation
routes was carried out through a fieldwork in the central part of Iquique.
Specifically, the analyzed area is bounded from north to south by Sotomayor
and Libertad streets (see Fig. ), which includes the historic
district and the area of influence of the port, alongside residential,
educational, and commercial activities. More than 45 km of evacuation
routes were assessed with the aid of video footage and Global Positioning
System (GPS) devices, which were used to geo-reference existing urban
micro-vulnerabilities that pedestrians could experience during an emergency
evacuation.
During the fieldwork, the following types of micro-vulnerabilities were
observed as the most common elements capable of hindering evacuation: (i) presence
of parked cars on sidewalks, (ii) narrowing of sidewalks to make
space for parking, (iii) use of sidewalks to extend the service area of
restaurants (only during the day and evening), (iv) use of public spaces for
informal commerce, and (v) road works. The last is a temporary type of
vulnerability; therefore, it represents a specific, non-regular condition in
the city streets (see Fig. ). These observations give rise to
the micro-vulnerability classification that is described in the following
subsections.
Among the identified issues, that of greatest concern is the presence of
parked cars on sidewalks. Due to the large dimensions of these obstructions,
the useful walkable area is reduced and the capacity of the evacuation routes
is considerably affected; in some cases, the available width of the sidewalk
is reduced to less than a meter, which in the event of an evacuation might
lead to bottlenecks that could increase evacuation times. In addition, there
are built parking areas that decrease the sidewalk width, called
“narrowings” in this work. The presence of these elements is related to
the public need for parking spaces due to the high motorization rate in the
city, which is among the top 3 % of Chilean communes with the highest number
of vehicles (the value of which is comparable with communes in the capital of
the country; ). It was observed that a large portion of
households, mostly old buildings, do not have private parking spaces, forcing
the residents to park their vehicles in public spaces.
Still frames obtained from field recordings in the city Iquique: improperly parked vehicles (a), informal commerce (b), road
repairs (c), and restaurant tables on the sidewalk (d).
Micro-vulnerabilities representation and classification
During the post-processing stage, elements that represent an impediment or
delay to pedestrians movement along evacuation routes, thus contributing to
the vulnerability of public spaces, were characterized through a thorough
analysis of the fieldwork-collected data. This process consisted in the
identification of the elements within the studied urban spaces that could
decrease the speed of evacuees, considering the scientific evidence from the
literature on pedestrian dynamics .
After the micro-vulnerabilities were identified, they were drawn on the map
of the city using geographic information tools (ArcGIS) in a planar
projection system, attempting to faithfully reproduce their dimensions in
order to generate a map that includes the micro-vulnerabilities existing
along each of the evacuation routes in the study area. The mapping of
micro-vulnerabilities using geographic information systems delivers
information regarding the characteristics of the element, its location, and
the surface area it covers, facilitating the organization, manipulation, and
analysis of the large quantity of data obtained (Fig. ).
Mapping of identified micro-vulnerabilities, colored according to their
taxonomy.
In order to generate a taxonomy based on the origin of the observed problems,
following the guidelines proposed by , they were grouped into
three categories: (i) inappropriate use, (ii) inadequate maintenance, and
(iii) problems related to the design of evacuation routes, the descriptions of
which are found in Table . This classification follows a
representation of the micro-vulnerabilities in terms of their origin and
also provides an indication regarding policies or regulations that could be
implemented at the municipal level to decrease their effects during future
evacuation processes. While the inappropriate use and inadequate maintenance
of routes can be rectified through easy-to-implement strategies, the problems
related to design would need more invasive measures.
Classification based on micro-vulnerability origin (modified from
).
TaxonomyDescriptionInappropriate useUnsuitable use and appropriation of the sidewalk for multiple uses other than pedestrian traffic, e.g., parking, restaurants, gardens.Poor maintenanceLack of care and repair of public spaces on the part of the relevant authority or individuals, e.g., broken sidewalks and manhole covers.Design problemsDifficulties present on routes associated with their planning and construction, e.g., sidewalk narrowings and stairs.Evacuation route obstruction level
In the previous section, the types of difficulties that a pedestrian could
encounter while evacuating along the routes of Iquique were described
qualitatively. Our research also provides tools to evaluate quantitatively
the detected problems and compare between evacuation routes. The
quantification of the micro-vulnerabilities and the obstruction levels of the
evacuation routes is defined through a proposed friction rate, defined as
i[%]=∑jSmj⋅αjSr×100,αj=1-SCVj,
where Sm is the surface area of the micro-vulnerability associated with an
evacuation route, Sr is the surface area of the analyzed evacuation
route, and
α is the speed reduction factor associated with each micro-vulnerability.
This indicator represents the proportion of the area of an evacuation route
that is occupied by the micro-vulnerabilities existing on it. To distinguish
how pedestrians are affected when confronted with a given
micro-vulnerability, the factor α is defined to quantify their speed
reduction; therefore, the effect of each element is weighted differently in
the friction rate. The factor α is the complement of the magnitude
defined as speed conservation value (SCV)
, which represents the percentage of the maximum speed
that can be maintained on a given surface (Eq. ). To this end, each
micro-vulnerability was classified according to one of these categories: (i) blocking
or decrease in spaces available for evacuation, (ii) abrupt surface
level changes, and (iii) noticeable changes in surface roughness. Where the
maximum speed is reached on compacted and flat ground such as street pavement
and sidewalks , speed is completely conserved
and SCV is 1.
For each micro-vulnerability, a SCV value was assigned (see Table ).
For elements where passage through is not possible and
they thus represent a blockage of pedestrian movement, the value of SCV is null.
Among the observed micro-vulnerabilities, there are some which do allow
passage, but involve a change in the normal speed of movement, such as level
changes that require pedestrians to make an additional effort to continue
onward, and changes in surface material that translate into more difficult
movement. The chosen values were selected from literature regarding
pedestrian speed measurement in various situations; in the case of level
changes, the SCV was defined as around 50 %
and, for surface material changes, around 90 % .
Speed conservation of micro-vulnerabilities present on evacuation routes.
In summary, Eq. () represents the sum of all the areas of
micro-vulnerabilities on a particular evacuation route, individually weighted
by a speed reduction factor based on experimental literature review (Eq. ).
The friction rate is the quotient of this sum and the total
surface area of the evacuation route, which is then multiplied by 100 in
order to work in percentage terms. The analyzed area comprises evacuation
routes with similar road dimensions along its length; therefore, the total
evacuation route surface area is used, making it possible to analyze the
contribution to vulnerability of cars that are completely or partially parked
on the road. In cases in which the dimensions of the road's cross section
varies among the analyzed evacuation routes, separate analyses of the
sidewalk and street may be done.
Results and discussion
The purpose of calculating the friction rate at evacuation route level as
defined in the previous section is to have a measurement of the effect of
micro-vulnerabilities on the available space for the movement of evacuees
along each evacuation path, allowing a comparison of them and to determine
their relative degree of vulnerability. This provides a useful tool to prioritize
focus zones and develop more accurate evacuation models in these areas.
This index includes the sidewalk and street surfaces to represent the
obstruction level of the evacuation routes, but it removes the cars
circulating on the street from the identified micro-vulnerabilities due to
the variability of this condition. The high motorization rate in the city and
the history of vehicles used in previous evacuations pose
a negative precedent and undoubtedly increase the vulnerability of people
during an evacuation, as they restrict movement of pedestrians mostly to the
sidewalk (see Fig. ).
Preventive evacuation of 16 March 2014 .
Friction rates obtained for the evacuation routes in the study area.
In Fig. , the results of the friction rate calculations for
the streets analyzed in this study are presented graphically. It is shown
that the highest friction rates are concentrated in the central part of the
study area due to its status as the most active zone of Iquique's downtown,
which is the result of the high presence of educational institutions, office
buildings, and commercial facilities. The maximum friction rate value for
O'Higgins Street (an evacuation route that in some stretches at the moment
of the study was affected by road work) verges on 20 %. The second route with
a high friction rate, Latorre Street, is an area of concern due to the
quantity of people that would arrive during an evacuation, especially since
it provides the shortest means of access to the safe area for part of the
population that resides on the peninsula south of the port (around 530 people).
Continuing with this analysis, the rest of the population of the
peninsula (around 780 people; ) must evacuate by Zegers Street,
the third evacuation route, which has a large number of micro-vulnerabilities
along its entire length.
The port area deserves special attention due to its large distance to safe
areas. In this respect, representatives of the Iquique Port estimated that in
a worst case scenario there could be more than 1500 workers. Fortunately,
the evacuation routes accessible by the Iquique port's personnel, Esmeralda
and Bolívar streets, have low friction rates. However, the greatest problem
for workers is the time it takes to leave the port and reach the mainland
safe area. Considering the aforementioned observations, the major concern in
Iquique downtown is Zegers Street due to its high friction rate and nearness to
coast unlike Latorre Street; in contrast, O'Higgins Street must be
removed from this analysis due to the temporal elements contributing to its
friction rate during the fieldwork. The rest of the evacuation routes show
lower friction rates, but some speed reductions and flow capacity decreasing
of evacuation routes are to be expected. By gathering all the
micro-vulnerabilities and adding its contribution to the friction rates in
the study zone, it is possible to deduce that the main issue is the
inappropriate use of urban space to parking on either the sidewalk or street,
with around 74 % of the whole friction contribution. One of the most
illustrative outcomes of the developed methodology is to provide means to
assess the drawbacks of using sidewalk for parking, generally perpendicular
to the road, with the effective width of the sidewalk sometimes decreasing
from 4 to practically 1 m. Through the presented methodology of
micro-vulnerabilities identification is possible to pinpoint urban problems
related to evacuee displacement, quantify its impacts, and prioritize
solutions with different complexity levels.
In Chile the definition of threatened and tsunami safe areas, along with the
elaboration of evacuation plans, is the duty of National Emergency Office (ONEMI),
while the Ministry of Housing and Urbanism (MINVU) is responsible for urban planning and
development management and also defines the use of urban spaces. Nevertheless,
the execution and supervision of higher authorities plans is in the hands of
municipalities. This institutional fragmentation leads to different urban
risk reduction approaches. Despite this, efforts haven been made to
standardize the urban planning procedures related to tsunami evacuation
infrastructure .
An interview with personnel from the regional branch of the National
Emergency Office and the municipality of Iquique was conducted as part of the
field survey, where the plans related to evacuation improvement were
discussed. These authorities put forth ideas for improving evacuation plans
and infrastructure, among which was the creation of main routes intended
exclusively for pedestrian use during an evacuation. Internalization of
evacuation procedures among the population was highlighted and concerns about
the use of cars during the last evacuation process in 2014 were also mentioned
during the interview. As a result of this study a series of mitigation measures
that could be carried out at the municipal level in Iquique, is proposed in
order to improve the urban design for evacuation. The most direct is
the regulation of parking in public spaces by using city council
attributions like fines in areas near to the coast. Other measures like the
creation of additional parking spaces on streets perpendicular to evacuation
routes, installation of elements that impede the passage of cars onto the
sidewalk, and removal of abandoned vehicles are strongly recommended.
Likewise, temporary activities such as informal commerce and dining must take
place only on streets not meant to be used as evacuation routes. The
implementation of such modifications must take into account possible effects
on existing traffic and the local economy as well as sociopolitical
reactions.
The presented results demonstrate the existence of urban
micro-vulnerabilities in the study area and characterize their effect in
tsunami evacuation processes. However, the fieldwork was undertaken during a
specific time window and no time evolution analysis of the locations of the
micro-vulnerabilities on the streets of Iquique was carried out. Updating the
friction indexes would require a semi-continuous survey of the evacuation
streets, which could be performed using, for instance, closed-circuit
television (CCTV) systems available at the municipal level. Doing a temporal
analysis could be possible through automated micro-vulnerability mapping
processes using tools for object detection in images as well as satellite
images of extremely high resolution and capture frequency. However, it is worth
noting that the present study examines a situation as close as possible to
the everyday nature of the city, i.e., during a non-holiday time of the year
and day of great work, educational, and commercial activity.
Conclusions
Tsunamis are one of the natural hazards of greatest concern for coastal cities
and port areas, especially in Chile, whose maritime border is close to one of
the most active tectonic plates. To mitigate their potential impacts, joint
efforts and actions are needed, including political, technical, financial,
and cultural. Tsunami education and evacuation drills programs had good
results and were demonstrated to be effective during the 2014 and 2015 Chilean
tsunamis , but these events had lower magnitude
than the 2010 tsunami disaster. The last two events have allowed us to assess
the response of coastal cities against lower-magnitude events and to develop
new strategies for the continuous improvement of the evacuation response
against major tsunamis. Improving the environment and the ability of the
community to adequately react when confronted with a great disturbance is
fundamental, since limited preparedness gives rise to vulnerable environments
.
This article highlights the importance of evacuation routes, public spaces
intended to multiple uses that also support tsunami evacuation, and the
assessment of the built environment condition. The potential reduction in
evacuation capacity from urban micro-vulnerabilities associated with planning,
use and maintenance problems, and their influence in the displacement of
people to safe areas is evaluated. The decrease of the effectively available
pedestrian area in evacuation routes caused by the presence of sidewalk
obstructions was identified as the greatest problem in the city of Iquique,
which could worsen over time due to the higher activity and population growth
trend in coastal areas. When city planning is tackled considering urban
improvements aimed at increasing resilience at both the macro- and microscales, the built environment could improve the people response in case of
emergencies. The construction of high-rise buildings has increased lately;
the possibility of using them as vertical evacuation shelters must be
carefully analyzed, taking into account their seismic design, capacity, and
resistance to hydrodynamic forces. The availability of buildings for vertical
evacuation purposes would considerably decrease the flow of pedestrians,
prompting safer evacuations. In particular, their use is strongly recommended
for evacuating workers from the port of Iquique , which
is the district most exposed to tsunamis, due to its distance
to safe areas.
As mentioned in Sect. , the main issue in Iquique is
related to cars use. The contribution of other micro-vulnerabilities to the
friction rates and their effect in the decreasing of flow capacity of
evacuation routes is lower, with the presence of informal businesses,
restaurant expansions, and trees on the evacuation routes, which have values
between 2 and 3 % of the whole friction factor. For the purpose of decreasing the
existence of micro-vulnerabilities, measures can be taken at the local level
by municipal authorities. The inappropriate use of evacuation routes can be
rectified through restrictions and fines designated by the municipality.
Likewise, methods can be developed to monitor the possible public space
difficulties generated by inadequate route maintenance. Finally, problems
related to design are the most difficult to reverse and can be corrected
through the construction of new works or retrofitting of existing areas, with
evacuation efficiency taken into account as an important driver.
The road network and the critical infrastructure of a city play an important
role during an emergency and may be also vulnerable to earthquake damage.
For instance, the failure of power supply and debris from damaged buildings
could further reduce the routes' evacuation capacity, in addition to existing
micro-vulnerabilities. Generally, the identification of urban
micro-vulnerabilities is not been carried out on large scale, and investment
in mitigation measures is not a main concern in developing countries. In near-field tsunami-prone areas, where the available time to evacuate could be very
short, like Chilean coastal cities, urban micro-vulnerabilities could make
the difference in the evacuation process performance. If the evacuation
routes remain clear and free of obstacles, the evacuees' movements could be
faster and the overall tsunami evacuation time could decrease and potentially
save lives. The assessment of evacuation routes condition should be done
regularly, especially in South Pacific countries with high seismic and tsunami
risk, where the environment showed by maps and plans is commonly different
from the reality that pedestrians experience.
Efforts to create a more resilient city must not be undertaken only after a
disaster; they should be incorporated in the decision-making process of city
planning. The implementation of culturally sensitive education and awareness
programs to efficiently communicate potential risks associated with
inappropriate uses of public spaces should be considered in order to reduce the direct
impacts of natural hazards and improve the resilience of tsunami-prone
communities.
Video records are available upon request from the corresponding author.
Figures 1a, b, 4 and 6 were made using ArcGIS software, shapefiles data can be requested from corresponding author.
Figure 1c was obtained from a Python code, using the tide level data from http://ioc-sealevelmonitoring.org/ (last
access: 20 April 2018).
The study was conceived by JL and RC, and the methodology was
designed with the contribution of all authors. GA and MQ carried out the field
survey with the supervision of JL and RC. The video records postprocessing
stage was developed by GA and MQ. GA carried out the data analysis and prepared the first version of
the manuscript with the guidance of RC and JL. All authors contributed to
editing the final version of the article.
The authors declare that they have no conflict of
interest.
Acknowledgements
This research was supported by the Research Center for Integrated Disaster
Risk Management (CONICYT/FONDAP/15110017). The authors are grateful for the
information provided by the Iquique Municipality, the Tarapacá office of
Chilean Emergency Management Agency, ONEMI, and the Port of
Iquique. Edited by: Mauricio Gonzalez
Reviewed by: Harkunti P. Rahayu and Pino Gonzalez-Riancho
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