The ISDR is an organization that works to reduce the impact of natural disasters by updating buildings, writing legislation, and increasing education and awareness about disasters. As a tool on the ISDR site, you can take control of a town or city's well being as a planner. Your job, as a player, is to ensure the safety of the people and structures while meeting requirements for education and medical assistance.
For this disaster, the tsunami option was chosen but other choices are: wildfire, flood, hurricane, or earthquake.
The strategy to prevent casualties was to buffer the coasts with natural barriers such as sand dunes and mangroves but the highest priority was to educate and implement the warning systems available from the city center. Regardless of how many barriers you have, if nobody knows what’s going on, more people will die. Next priority was to have ample housing to hold and protect as many people as possible while having the resources to educate and warn them of eminent disaster.
After running the simulation, you can see that anything in the first few rows along the ocean front was destroyed without question and unprotected buildings inland were destroyed. This shows how important it is to allow a buffer between the shore and buildings or other structures. If built too close and a tsunami was to hit, the damage costs would be devastating as well as the loss of life.
This time, the simulation will be created in a way to maximize damage as well as loss of life to demonstrate the previous discussed ideas. Here you will see how a dense population in the direct path of a tsunami would be damaged. To imitate a resort area, all natural barriers such as sand dunes and mangroves were also removed exposing even more of the shoreline to the wave.
The simulation clearly demonstrates the vulnerability of unprotected, poorly planned ocean front property. All large occupancy buildings located near shore were destroyed as well as the smaller, weaker homes built beyond those resorts.
Now this was just a simulation, but shows you perfectly how important it is to educate people and update structures against hazards. We can work together to help increase awareness about the risks environmental hazards and work to adequately respond when they occur.
For more information about disaster reduction and the ISDR, please visit:
Risk and Hazard Assessment using
ArcGIS software
Geospatial
information systems, or GIS, are one of the fastest growing fields in any
industry today. Since the digital age is upon us, government agencies as well
as private organizations are now using GIS software to organize and communicate
information. Using the Internet, ESRI ArcGIS is setting industry standards and
through the use of Arc software, spatial information is available around the
world with the click of a mouse.
GIS is a tool
that industry professionals can use in many applications, a couple being risk
assessment and hazard location. Using the ArcOnline data base, multiple layers
of information can be added to a map and analyzed to find “high risk” areas.
The map below is the start of what is possible through GIS technology and
resources.
This map roughly
depicts the geospatial relationships between frac sand mines, as well as
hydraulic fracking locations, to regional aquifers in the Midwest using data
available through the ArcOnline data base. Recently, the process of hydraulic
fracking has boomed creating a demand for silica sand or frac sand which just happens to be
nestled in western Wisconsin counties. The new industry has potential to cause
health risks from depleting air quality to tainted water sources. Studies thus
far have shown little detrimental effects from sand mining but long term
effects are still unknown. Rail networks which once lain dormant are now being
used once again to transport sand to the mining sites across the country
creating potential for accidents and increased operating/maintenance costs.
Water sources are under appreciated here in the Midwest due to the Great Lakes
in our backyard, but we can’t forget about the million dollar recreational
industry we have for lakes and rivers in the region. If a mining malfunction
were to “poison the waterhole” so to speak, millions
could be lost not only for the mining business directly but the environment and
states as well. The mining community has taken an engineering view on reducing
the risks of the mining operations as well as other environmental impacts
(although sometimes these are overlooked and disaster strikes such as the deep
water horizon rig explosion). Fracking uses reservoirs to hold liquid waste
from the mining process creating the possibility of leaks, or exposure flood
waters if not carefully planned and constructed.
Using ArcGIS, it
is easy to visually depict and locate higher risk areas to avoid or restructure
as well as perform analysis on how to respond if something were to go wrong.
GIS technology allows for the user to plan and test evacuation plans,
numerically find how many people a hazard could effect, or even help to prevent
a disaster in the first place. A government could use GIS if necessary data are
collected. Weather patterns, detailed regulation reviews, and relatively accurate
census records are a few data sets that are keys for disaster planning. If a
disaster would occur, the areas that were impacted the most should be cataloged
so proper mitigation could occur in the clean up and rebuilding. GIS is can be
one of the most effective tools for hazard planning and response.
Earthquake Damage Analysis using ArcGIS
As previously discussed, GIS technology can be an extremely helpful tool especially when working to understand natural hazards and disasters. In this section, historic earthquake data along with building information and geologic surveys are used to inspect areas that are prone or at high risk of being damaged.
The western region of the United States in which a high frequency of earthquakes occur, would benefit from the help of a GIS. The use of the geologic surveys allowed areas of quaternary deposits to be mapped over earthquake histories. Areas that show higher levels of shaking from earthquakes also hold some of the larger deposits revealing a useful relationship to planners. Now with urban all urban areas add to the US, a spatial relationship between the three is hard to decipher. Using the GIS technology, selecting only those urban areas that fall over a quaternary deposit or in an area that experiences high probability of shaking are selected and mapped. The limited selection allows those urban areas at a particularly higher risk to be highlighted allowing residents to be more informed as well as future builders.
In a more focused area of interest, overlay analysis is also helpful. The top map displays the areas that had the highest density of building damage were also the areas that had the highest number of buildings deemed unsafe. So we add to this information as we move to the center map. Area quake stations are scattered around the city but seem to be located away from the highest damaged areas. To improve response time and data collection for future analysis, new stations could be placed closer to the areas of high damage. These high damage areas also overlap those areas that experienced the highest levels of ground acceleration or movement. The high amounts of movement adds to the building damage, especially if you remember from the top map, that those buildings were unsafe to begin with. The bottom map echos the center only instead of acceleration, ground velocity is compared to damage density areas. Highest velocity areas were too located in those that experienced the highest levels of damage. Northridge had the trifecta of high risk: weak, unsafe buildings, high levels of acceleration and high velocities caused by aftershocks of the earthquake.
Monitoring Volcanic Risk with ArcMap and ArcScene
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World Countries leading in volcanic eruptions. The deeper
tone of red, the more eruptions have occurred since 79 A.D. Most of the
eruptions are located in those countries on active tectonic plate boundaries.
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Many volcanic eruptions are caused by movement of the Earth's tectonic plates. Being able to layer a map of countries of the world over the location of the plate boundaries, we can see which countries lie near or on those boundaries. Using historic records and geologic information, we can also use ArcMap to symbolize those countries that have experienced more eruptions than others. This information can be helpful in determining where in the world the highest risk is and where may need the most help in the future if not prepared for potential eruptions. Now to take the topic a little closer to home, we will look at the risks surrounding Mt. Rainier and Mt. St. Helens in Washington State.
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| These are digital elevation models (DEMs) for Mt. Rainier. A DEM gives a 2-dimensional representation of the elevation and topography of an area. The variation in values can be set in black and white, or with a color ramp as depicted below. In the top image, white areas are those at higher elevation where black are areas at low elevation. The bottom DEM shows high elevations in white, low elevations in light blue and intermediates in red and yellow. |
The digital elevation models (DEMs) shown above depict the elevation and topography of Mt. Rainier on a 2-dimensional scale. Low areas are vulnerable to the effects of an eruption since lahar flows will follow rivers and valleys in the terrain. Using ArcScene, we can show just exactly how those lahars have traveled in the past in both a 2-dimensional and 3-dimensional representation.
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| A triangular irregular network (TIN) is a 3-dimensional representation of the topography of an area. This TIN depicts the same view of Mt. Rainier as shown above in the DEMs. |
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| The scene above is a combination of the TIN layer and the DEM of Mt. Rainier. By using the TIN as a base for 3-dimensions for elevation, the DEM can be "draped" over the TIN creating one 3-D model. |
In ArcScene, a user can create triangular irregular networks or TINs. A TIN is a 3-D model of the topography of an area while the DEMs are only 2-D. By assigning the TIN values as default height for the DEM, a user can display a DEM in 3-D. Since elevation is not the only influence on the path of lahar flows, we can evaluate how and where a lahar would flow depending on land cover around Mt.Rainier.
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| This model using a land cover DEM and TIN of Mt. Rainer depicts where historically lahar deposits have been found and are likely to form again if an eruption were to occur. |
By using digital modeling to evaluate historic impacts of lahar around Mt. Rainier, residents of Seattle and Tacoma can better prepare and plan in case an eruption were to occur. Most of the lahar deposits have formed on the southern face of Mt. Rainier, opposite the cities. Not to say lahar flows aren't a danger to the cities, but the areas of highest risk are those on the southern face at low elevation or valleys. Around the face of the volcano, lahar is spread more evenly without the restriction of dense vegetation. The valleys of dense woodland forest and the low elevation help to corral and focus the flows. So now that we know a little about pre-event evaluation and mitigation, lets look at information about the 1980 eruption of Mt. St. Helens.
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| The aerial photo to the left depicts Mt. St. Helens before the eruption. The right photo shows the same area after the eruption in 1980. The north face and entire peak of the volcano blew causing a drastic change. |
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| The left image shows areas on and around Mt. St. Helens that experienced a change in volume, primarily a loss as a result of the eruption. The right depicts areas that were changed the most by the eruption. The peak and northern face of the volcano where the eruption was the most violent clearly are shown. |
The 1980 eruption resulted in a cloud of rock and ash miles and miles tall stretching into the stratosphere. As a result a large volume of rock was thrown down and away from the volcano creating large amounts of air-fall tephra to the surrounding area. Boulders were thrown through the air as part of the tephra, making anything within the fall-out zone vulnerable to damage. By reviewing areas that experienced volumetric changes, future development and safety zones can be established to eliminate some of the risk from air-fall tephra as well pyroclastic flows.
Mass Wastage Risk Assessment
Mass wastage events more commonly known as slope failures, rock falls, flows, slides, or subsides are when a large amount of earth is suddenly set in motion posing high risk to those in its path. Depending on geology of the soils and bedrock, slope, and rainfall, different areas are more susceptible to failures.
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| The mountain ranges are highlighted by the areas of high susceptibility to land failures. Areas with moderate to low risk are those along extensive river systems such as the Mississippi. Appalachia is especially prone to failures with the high rainfalls and topography of the landscape. |
Development of an area, high amounts of rainfall, areas with thick deposits of fine-grained materials, upland areas that are exposed to seismic shaking, and environments with high relief are all at a higher risk for a mass wastage event. California is subject to main different varieties of hazards both natural and anthropogenic. The next couple images will take a look at a community and surrounding area that has experienced several wasting events.
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| Forest Falls, California is nestled in the northern valley of the photo displayed above. The danger of a slope failure is increased since the slopes surrounding the valley are all classified as 30 degrees or higher (yellow to red). With the face of the slopes susceptible to these failures covering a large area and the valley relatively small, the material possibly released in a failure has little space to occupy in the valley. |
As the slopes of the terrain increase, the more friction is necessary to keep that material solid. If heavy rains or snow melt occur, the water saturates the soil in turn reducing the friction on the particles making failures more likely. Slopes that have an angle of inclination of 30 degrees or higher are at higher risk of collapsing and failing. The next image will assess how poor city zoning of Forest Falls impacted the extent of damage from a failure in 1999.
With the city being built in the valley at the base of steep slopes, the risk of a slope failure causing damage is inevitable but how much damage is actually caused can be limited. From the image you can tell that the stream that passes through the city was moved artificially. This created a false security that the water was controlled. The change in position provided rain water and debris a second path to follow through the city. The watershed pictured displays the drainage of the system that recharges that stream and with the elevation gradient shows how that water is funneled straight into the city. The city needs to use the information from events like these to properly zone the areas in the direct path of a flow to protect the residents of Forest Falls.
Flooding Assessment for Regional and Coastal Areas
There are several types of flood events that can pose risks to near by populations. Some of these types include: regional floods, flash floods, and coastal floods/surges. In this section, regional flooding caused by engorged rivers at inland locations and the risks posed by coastal tsunami surges will be evaluated.
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| Eau Claire, WI, USA 100 year flood plain. The areas highlighted in blue are those expected to be flooded by an event that has a 1% probability of occurring each year. Structures in yellow are buildings located on the University of Wisconsin-Eau Claire campus. |
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| The photo above is a 3-D model of UW-Eau Claire Campus (oblique looking towards south) in the event of a 100-year flood. The pink structures represent buildings on campus and the blue regions representing the flood plain. In the 3-D model elevation is able to be physically represented as the lower elevations are cream or light green around the river, the higher elevations are the darker greens and reds. |
Evaluation of a regional flood in Eau Claire, Wisconsin is displayed in the couple images above. The images display a region of the 100-year flood plain for the city. A 100-year flood isn't one that occurs once every 100 years like the name suggests, but a 100-year flood is an event that has a 1% chance of occurring every year. This is a common misconception which can create a false sense of security for some residents. From the images, it is easy to determine those areas at risk for flooding during a 100-year flooding event. The low elevations surrounding the river are very flat and gradual making any increase in water level of the Chippewa River noticeable around the community. Eau Claire, as a mitigation effort has purchase some area in the 100-year flood plan and rezoned it to public instead of residential districts. Having open parks flood is much less costly than having hundreds of homes. Using elevation data, a GIS savvy individual can locate other flood plains such as the following. By using raster calculator tools in ArcGIS, areas at different elevations can be isolated allowing the user to visualize, symbolize, and analyze different levels of flood plains. Areas highlighted in blue will be flooded by an event that exceeds 790ft sea level (Left) and 800ft sea level (Right).
The event of a river spilling over its banks would be termed a regional flood. In tsunami and other wave surges, coastal areas can be flooded causing major damage and casualties if proper warning and response strategies aren't in place. Two locations will be assessed for risks involving loss of life and property.
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| This figure compares population densities to flood water depths. Those tracts with higher population densities are darker gray to black in the display as with flood depths increase as the blues darken. Areas of dense populations are located in some flood areas that will experience 10-15ft flood depths and without proper evacuation have a high probability of injury or death. |
Dense populations of low-income residents are at a higher risk than those of higher socioeconomic status. With money comes the ability to prevent, reduce, or recover from a hazard event. Little or no funds to help support hazard mitigation in low-income neighborhoods leaves the door open for high casulaties not only directly from the event but from the lack of recovery and support following the event. Cities need to invest in all residents not just those lucky enough to afford luxuries.
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| City zoning and construction frequently tends to overlook the chances of hazard events. The figure above displays the facilities that would be damaged or destroyed by tsunami surges in Oxnard, California, USA. 3 Hospitals, 10 emergency posts, and 42 schools are in the direct path for a tsunami event. If an event were to occur during a time where these facilities were to be occupied, lossed could be catastrophic. By locating these facilities at risk, the city can take action in educating people and creating effective evacuation routes. |
Oxnard, California is on the a city located on the sunny beaches of the western US. Tsunami events are capable of impacting the west coast meaning that cities such as Oxnard need to be aware of potential risks. The location of key facilities such as hospitals or law enforcement centers are crucial to the community. If these were to be lossed, recovery and treatment for those injured would be delayed which could be the difference between life or death. Because the city is built in the valley on the shore, the low elevation makes the city vulnerable to such surges.
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