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
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