Abstract
Light detection and ranging (LIDAR) technologies have been
in use over the last decades in the efforts to enhance the disaster management
platforms. Its coupling with the unmanned Aircraft systems (UAS) it has become
even cheaper, accurate and easier to use in the recent times. The two
technologies have been of great influence in the disaster management cycle with
their use being instrumental during the reduction, readiness, and response and
recovery phases of disaster management. The combination of the two technologies
has further enabled the stakeholders to achieve more efficient and accurate
geospatial information. The LIDAR mapping systems consist of
three very efficient components that make it stand out in all other remote
sensing technologies. It contains the laser ranging system, an inertial
measurement unit (IMU) and the global positioning system (GPS). Just like any
other systems and technological pieces, the LIDAR and the UAS systems are
marred with challenges and shortcomings of their own. However, the technologies
have witnessed growth in the recent times with more software and hardware
upgrade being adopted to increase the accuracy and efficiency of the system.
The effort to enhance the systems is as a result of identification of the
system as the leading technology in the survey and mapping industry
Acronyms used in the research
LIDAR- Light detection and ranging
UAS- Unmanned Aircraft systems
IMU- Inertial
measurement unit
GPS- Global
positioning system
NWS- National Weather
Service
DEM- Digital
elevation model
USGS- United States Geological Survey
NOAA- National Oceanic and Atmospheric
Administration
USA- United States of America
Introduction
In the United States alone, flooding
kills more people in the long-term than any other weather related disasters
witnessed in the country. Floods are capable of destroying buildings, roads,
schools, uproot trees, cause mudslides, destroy crops and further threaten
human life (NOAA/NWS, 2005). On a large scale floods are difficult to monitor and
have been sources of a head ache to many geological experts and disaster
management agencies around the world over the years. They are even more
sophisticated in monitoring due to their determination by some other local
conditions such as the slope of the terrain, drainage networks, protective
structures, land cover and even precipitation among other factors. There is,
therefore, the need to monitor every other coastal area and even the rivers at
different places along their course which can be difficult. Some floods happen
periodically whereas others happen on an annual basis with other happening at
random and unpredictable times (Harman et al., 2014).
According to the National Weather
Service (NWS), the flooding severity may also vary from minor flooding,
moderate flooding and major flooding (2005). The minor flooding results to
minimal damages to property but may pose a threat to the public or cause some
inconveniences. Moderate flooding causes some destruction on buildings, and
there may need to evacuate the residents in the event of its occurrence. Major
flooding, on the other hand, is very intense causing extensive damage to
infrastructure and may require major evacuate of the human population to higher
areas. In the case of seawater, the
disaster can be far more reaching (Webster et. al., 2006)
The flooding in coastal regions occurs
when the sea height exceeds the elevation of the land usually where there is a
form of a natural barrier such as dune system acting as the sea level. There
are also some human-constructed barriers such as levees may be overpowered by
swell conditions of the sea during storms or unusually high tides. The barriers
may also be breached especially on the open spaces along the coast. The steady
water flow may result in significant destruction and loss of life along the
coastal region. Horizontally, the water surge may fan out for hundreds of miles
along the coastline. The higher the intensity of a storm and the closer a
community lives to the coast, the bigger the impact of the flooding that
results from the upsurge of the waters (NOAA/NHC, 2014).
Coastal areas have always been at a
very high risk of flooding, but there is a likelihood of increased the risk of
flooding shortly due to the anticipated impacts of climate change. Such changes
may be the rise of the sea level and also the increased rainfall intensity
around the world. The changes will likely cause the areas that were previously
flooding to flood more frequently or the effects of the flooding felt more than
ever. It may also result in the witnessing of flooding in other areas that were
previously not experiencing the flooding. Hence, the need to employ more
technology and approaches that enable evaluation of the coastal flood risks in
an attempt to be prepared and also sufficiently address and manage the
inevitable disaster that comes with flooding (NOAA/NHC, 2014).
Since the acquisition of the aerial
photography from a hot air balloon in 1858 over Paris in France man has made
significant progress in the acquisition of remote sense data using platforms of
aircraft, satellite, space shuttles, model planes and the famous unmanned
aircraft systems (UAS). With the analysis of data from remote sensing data
obtained through methods such as Light Detection and Ranging (LIDAR), we can
now be in a position to parameterize the flood models, delineate the extent of
the floods and also estimate the damage of the flood. Coupling the UAS and the
LIDAR systems we can now not only act in a reactive manner during a flooding
event but can also is proactive through the flood risk analysis and mitigation
made possible by the technologies (NOAA/NHC, 2014). The flood hazards, exposure
as well as the vulnerability levels can be able to be motored and assesses
through remote sensing made possible by the LIDAR mounted on UAS. The flood
risk management, as well as disaster management strategies towards the flooding
menace, have been empowered and made possible through the technologies of the
drone as well as the advancement in remote sensing systems.
The UAS is a faster method of data
collection that fits between the vast areas satellite and smaller coverage.
Mounting a LIDAR on the UAS makes it possible to take to the skies virtually at
any point the experts feel like collecting the necessarily referenced images
required without the hassle of having to wait for manned aircraft or satellite
imagery. The UAS has offered the all necessary accurate aerial data that has
been in demand especially among the disaster management agencies (Klemas,
2013). The LIDAR system deployed through the UAS incorporates its remote
sensing method that uses light in the form of pulsed laser to measure the
ranges to the Earth. It is the light pulses coupled with other data recorded by
the airborne system that generates the precise, three-dimensional information
necessary for disaster management among them the evaluation of coastal flood
risk. Therefore, the UAS deployment of LIDAR is the most effective method of
assessing the coastal flood risk making flood risk management easier and more
efficient.
Usage of the UAS deployment of LIDAR to
evaluate Coastal flood Risk
The usage
of UAS deployment of LIDAR to evaluate Coastal flood risk has revolutionized
flood risk management in the world. The concept of flood risk management is
widely embraced over the past decade, and more and more nations are adopting
the idea. It has led to the deliberate changes in decision-making practice
highlighting the risk management as a potentially more complex but efficient
and dynamic model of addressing the problem of flooding. The requirements of
protection and belief in the people’s ability to control floods started
increasing in to dominate the attempts to deal with flooding. The emergence of
the flood risk management came with it the perception of the flood management
as not only an engineering pursuit but as a social endeavor (Klemas, 2015).
Throughout the 1960s, the attempts to address the flooding menace remained on
more physical flood control efforts such as the building of levees, dikes,
dams, diversion channels and other related structures. However, as the
population grew over the years, the impact of flooding continued to increase
and hence the need to do things in another approach. There was the need for an
approach to that would utilize the concept of risk management in the
decision-making process. It is this that encouraged the incorporation of
technology to the disaster management and risk management endeavor. It led to
the findings on the use of UAS and the LIDAR to be able to predict and mitigate
flooding. With the employment of the technologies, it has resulted in an
increased efficiency of risk management especially to flooding among other
disaster management endeavors (Webster et. al., 2006).
The LIDAR system as a remote sensing
method has played a significant role in the disaster management cycle.
Emergency management planning usually structured around the disaster management
cycle. The cycle is composed of 4 major stages namely the reduction, readiness,
response, and recovery. The remotely sensed data collected through the LIDAR
deployed through the UAS can provide the valuable source of information at each
stage helping one to understand the spatial phenomenon. It also provides the
scientists and the relevant authorities with the objective data sources
essential for decision making (Webster et. al., 2006). The major challenge
faced by disaster management is the inherent unpredictability and range of
hazards that does not allow for a single all-encompassing solution that needs
to be developed and also explored. However, it offers a variety of differing
remote sensing platforms and sensors employed for image acquisition.
The LIDAR remote sensing system can be
used to assist in reducing the risk through the identification of hazardous
zones associated with floods. It may also be used to verify the hazard models
by measuring the location as well as the magnitude of the actual events.
Imagery obtained through the LIDAR deployed by the UAS can be used by the
meteorologist for providing weather forecasting and also provide warnings of
potentially severe weather events providing the public and the emergency
responders with the right information that can assist in making decisions
around the short-term readiness. The imagery of disasters such as flooding is
widely shared in all forms of media as a way to offer warning and caution to
the affected persons. With the aid of the images, people that are at risk can
understand and acknowledge the severity or extremes of the lingering disaster
and therefore can take the relevant preparedness, mechanisms. For those that
respond to disasters, the images obtained may offer them the right form of
information necessary for preparing to mitigate and the impact of the disaster
including evacuation efforts if there is perceived an extensive threat to human
life. Remote sensing through the LIDAR can also be sued to provide the
indication of the rate of recovery in a given area post-disaster based on the
indicators such as vegetation re-growth and reconstruction which is crucial for
planning and emergency preparedness.
The LIDAR systems deployed by the UAS
can be very instrumental in the 4 phases of the disaster management cycle as
follows:
Phase 1: Reduction
Disasters have been proven to be social
constructs in that social driver have a role to play in the happening of such
catastrophes. Some of the social constructs include migration, conflict,
modification of natural systems, and overreliance on scarce resources, urban
pressure, artificial protection structures as well as economic and political
vulnerability. All these constructs are contributors to the people’s
vulnerability to the hazards. LIDAR as a remote sensing technology can be very
instrumental in addressing some of the disaster drivers through the proviso of
data required to assist the planners, and others tasked with emergency
management. The reduction or risk leads to the reduction of the probability of
a disaster to happen a very crucial part of disaster management cycle. The
LIDAR system can be paramount at a reduction of risk through identification and
the understanding of the hazards. It is the knowledge obtained that is used to
put in place some mitigation measures such as engineering structures, planning
and analyzing the consequences of the risks which is fundamental to reducing
vulnerability to such disasters (Webster et. al., 2006).
Understanding the magnitude, frequency,
duration, location, manifestation and range of a hazard is essential for all
disaster management endeavors. In as much as the social factors amplify the
occurrence of a catastrophe, improved knowledge of such hazards and their
potential consequences are essential to shaping up decision making about the
modification of hazardous characteristics. It can also be sued to derive
hazard-independent information that is critical to disaster reduction such as
baseline building and topographic mapping (Webster & Forbes, 2006). LIDAR
mapping for active fault location has been in use over time effectively.
Conventionally, fault location was conducted with stereo aerial photography
interpretation that was followed by intensive field survey. However, with the
use of LIDAR, there is horizontal and vertical resolution provided by the
airborne LIDAR imagery through its deployment in a UAS that provides the
capability for identifying the faulty traces and also extracting elevation
offsets with digital data in a very objective manner. The LIDAR technology has
been used over the course of time in useful ways. Such examples may range from
the Bridgewater Town LIDAR survey to assess the flood risk of the town in 2012
among other cities such as Lunenburg County in 2009. It is this evidence that
echoes the efficiency of the model (Webster & Forbes, 2006).
Phase 2: Readiness
With the realization that residual risk
from hazards has the potential to create emergencies and in some cases
disasters, some readiness planning and activities are embarked on. Readiness is
the process of the identification and also the development of the necessary
systems, resources and skills before the happening of a hazardous event. The
aim of readiness is to ensure that the response to the hazard is more
coordinated and efficient to make sure that the community experience lesser
trauma and recover on time (Webster & Forbes, 2006). Some of the readiness
attempt employed by a community or disaster preparedness agency are public
education, training and exercising, evacuation planning, developing hazard
monitoring strategies and public alerting systems as well as instituting state
and international plans and agreements for aid and assistance. It is such
readiness resulting that leads to the reduction of the impact of a disaster on
the community.
The information provided by the LIDAR
systems is essential and acts as asset information that makes the possibility
of readiness to the hazard attainable. Gaining familiarity with the most up to
date spatial information such as imagery as is provided for by the UAS deployed
LIDAR is crucial at assessing the damage during the response and recovery
phases. LIDAR is used to produce high-resolution hazard and risk maps to the
communities. It is the information provided by the remote sensing system that
enables individuals as well as disaster management agencies to have the
information about the location and range of hazards. If communities have the
crucial information on the risks, then readiness is possible hence mitigating
the impact and danger of such a happening.
Phase 3: Response
The response endeavors majorly focus on
protecting property as well as the lives of the people in case of a disaster.
Such activities include evacuations, sandbagging along the coastal lines,
search and rescue operations, evaluating the safety of buildings in the event
of flooding, establishing immediate emergency shelters as well as setting up
command post among other quick responses that come with response phase. LIDAR a
remote sensing technology may be very crucial in this phase at providing the
immediate damage assessment if the data is provided promptly. Incorporating the
UAS technology with the LIDAR system makes the assessment faster than ever
before since it is easier and quicker. The LIDAR systems contain information
and data that is crucial to enabling the making of evacuation plans through the
combination of observing the weather patterns and the hazard behavior.
Ideally, the recovery activities all
commence with the beginning of the response phase that is made possible by the
imagery and other data collected by the UAS deployment of LIDAR to evaluate the
flood risk. It is at this point that process of recovery is kick-started in a
holistic manner. It means that the assessment of damages undertaken through the
remote sensing during the response phase is integral to the recovery phase as
well. At the stage of recovery, the temporal relevancy of the LIDAR provided
information is very critical to allowing disaster managers to make effective
plans for mitigation on the dynamic solutions readily available to them. The
near real-time information from the system offers the coastal risk management
to plan how to address the flooding menace and as a result leads to the saving
of resources and time ultimately saving lives as well. The information that is
usually of sufficient spatial resolution also allows the detailed tactical
assessments and decision-making ion the flooding condition.
Phase 4: Recovery
The use of the remote sensing
technology such as LIDAR in the recovery efforts is the least developed
technology in this area. However, the remote sensing can make critical
contributions to the provision of objective time series over a large area that
have both high and medium levels of spatial detail. In other specialization,
the time series analysis of the remotely sensed data is a well-established
practice. In the disaster management and primarily the recovery phase, some
very clear indicators can be easily measured and also monitored with LIDAR
imaging made possible by its deployment by the use of a UAS. Some of the indicators
may include the construction and the following removal of the medium and
long-term emergency shelters, removal of debris, starting and-and completion of
construction or reconstruction of infrastructure such as buildings, roads and
bridges, re-growth of vegetation and also the reduction of siltation from the
waterways following a flooding event.
By the use of spatial resolution
provided b y the LIDAR systems, the amount of housing reconstruction can, at
least, be visually identified in the presence and also the absence of blue
tarpaulins covering the roofs following the devastating Hurricane Katrina event
(Webster & Forbes, 2006). The development of the UAS to deploy the LIDAR is
a step in the right direction at enabling an automated detection method that is
less time consuming to identify quickly and repeatedly in a series of data and
time set. Moreover, the analysis if time series imagery could also be crucial
at monitoring the efficiency of the various strategies. By extracting the
recovery rates from the data gathered at time intervals could help in
assessment and also assist in guiding future events of similar nature, it could
also contribute to identifying some of the areas of residual risk that may
require further monitoring until the physical recovery process is completed.
Advantages of UAS deployment of LIDAR
to disaster management