Geographic Investigation

 

“The extraordinary growth of cities in the contemporary era, however, points to the need for land-change research using a vulnerability approach in rapidly urbanizing locations.

Coastal zones are important sites for research because many of them are urbanizing rapidly and will likely face impacts from climate change. Will rapid urbanization render coastal ecosystems particularly vulnerable to the effects of sea-level rise and tropical storms in the 21st century? How will people’s culturally driven preferences for certain types of urban vegetation, such as turf grass, affect urban coastal ecosystems? Most important, how will these coupled human-environment systems respond and adapt to shifting exposures and impacts?” (UCP, 45)

“Advances in our understanding are most likely to be achieved through investigations that examine issues of resilience, sustainability and adaptation at local scales, and their relationships to larger scale processes.” (UCP, 48)

Sendai Airport, Miyagi Prefecture, Japan

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Japanese Tsunami, March 2011: Part 1

The video in the introduction gives you a glimpse of the human impact of the major tsunami off the coast of Japan. To understand more fully the extent of the flooding in the Sendai area of Japan, click on the “flood map” below.

Flood Map

Zoom in until you can see the Miyagi Prefecture and the City of Sendai in the center of the map window. At the top of the page, click the Sea Level Rise menu and gradually increase the sea level rise. Start at one meter. Observe and increase the height until you attain the height of the tsunami wave as mentioned at the beginning of the video.

e. Can you imagine how many residents of that area lost their lives, their livelihoods or were permanently displaced from their homes? 

To study more about the vulnerability of coastal inhabitants, continue on to investigate Japanese Tsunami, March 2011: Part 2.

Japanese Tsunami, March 2011: Part 2

In this investigation, you will explore the inundation event that happened on the east coast of Japan near the city of Sendai in the Miyagi Prefecture. This event combined with the Queensland, Australia tsunami makes 2011 famous for extreme coastal flooding events. The Japanese tsunami occurred as a result of an 8.9 magnitude earthquake. 

Read the following exerpt  (from the NOAA tsunami physics website):

“As the tsunami crosses the deep ocean, its length from crest to crest may be a hundred miles or more, and its height from crest to trough will only be a few feet or less. They cannot be felt aboard ships nor can they be seen from the air in the open ocean. In the deepest oceans the waves will reach speeds exceeding 600 miles per hour (970 km/hr). When the tsunami enters the shoaling water of coastlines in its path, the velocity of its waves diminishes and the wave height increases. It is in these shallow waters that a large tsunami can crest to heights exceeding 100 feet (30 m) and strike with devastating force.”

  1. Click this link to the  Esri Terrain Online Profile tool to see the profile of the bottom of the ocean (bathymetry) as well as the coastal land near Sendai, Japan.
  2. In the search in the upper right, type in "sendai" to zoom the map to our area of study.
  3. Click the Measure tool, choose Distance and then select miles or kilometers to explore the distance and elevation profile. Click to begin the line, then drag and double-click to end the line. When you are ready to start a new profile, just click once in the starting position and repeat the steps.
  4. Explore: Draw a line just off of the coast to the east of the city of Sendai. Look at the change in the ocean floor just before it meets the land. Record the change in feet just as the ocean meets the coast. Do this two or three more times. 

             f. Approximately how many feet does the elevation change (underwater elevation is called bathymetry) as the ocean bottom meets the coast? 

 

              Hint: Be sure to look at the Elevation in Feet on the y axis of the graph.

g. How did the ocean floor near the coast of Sendai influence the height of the incoming tsunami wave?

h. Does the ocean floor off of Sendai help protect or enhance the destruction of an incoming tsunami wave?

i.  Usually the ocean level goes down by as much as the incoming tsunami will raise the ocean level. This results in an outgoing tide particularly in long shallow shore physical geographies. Would the community of Sendai have had much warning before the tsunami wave struck?

Read this second exerpt (from the NOAA tsunami physics website):

“Tsunamis are characterized as shallow-water waves. Shallow-water waves are different from wind-generated waves, the waves many of us have observed on a the beach. Wind-generated waves usually have a period (time between two sucessional waves) of five to twenty seconds and a wavelength (distance between two sucessional waves) of about 100 to 200 meters (300 to 600 ft). A tsunami can have a period in the range of ten minutes to two hours and a wavelength in excess of 300 miles (500 km). It is because of their long wavelengths that tsunamis behave as shallow-water waves. A wave is characterized as a shallow-water wave when the ratio between the water depth and its wavelength gets very small. The speed of a shallow-water wave is equal to the square root of the product of the acceleration of gravity (32ft/sec/sec or 980cm/sec/sec) and the depth of the water. The rate at which a wave loses its energy is inversely related to its wavelength. Since a tsunami has a very large wave length, it will lose little energy as it propagates. Hence in very deep water, a tsunami will travel at high speeds and travel great transoceanic distances with limited energy loss. For example, when the ocean is 20,000 feet (6100 m) deep, unnoticed tsunami travel about 550 miles per hour (890 km/hr), the speed of a jet airplane. And they can move from one side of the Pacific Ocean to the other side in less than one day.”

Tsunami waves generally travel proportional to the depth of the ocean it is traveling through. An estimate of wave speed can be calculated using the formula.  

v= √9.8m/sec2 x ocean depth

Using the Elevation Profile tool again, click in the middle of the bay to approximately 25 miles out from the coast and then double click on the city of Sendai. Do this several times in a few different places in the center of the bay to get an approximate depth of the ocean floor from the bottom of the bay.

j. Based on the depth of the middle of the bay to the east of Sendai, what was the speed of the wave? (Hint: insert your ocean depth into the velocity formula above.)

k.  What new vulnerabilities do the residents in Japan face following this catastrophic event?

Summary

“Since the 1980s, global environmental change has emerged as an important research area in many academic disciplines. Geographical scientists have played major roles in a variety of international and interdisciplinary environmental-change initiatives, and have taken a leading role in bringing vulnerability issues to the fore.”(UCP, 42)” Advances in our understanding are most likely to be achieved through investigations that examine issues of resilience, sustainability, and adaptation at local scales, and their relationships to larger scale processes.” (UCP, 48)

Japanese Tsunami & Remote Sensing: Part 3

Now that you have watched the tsunami waves approaching the Sendai Prefecture shoreline and move over the land, can you imagine what the area looked life after the tsunami wave hit land and then receded?

Explore the before and after aerial imagery of the areas in Japan hit by the tsunami wave. Click the link. "Swipe" back and forth on each image with your cursor to get a sense of what the landscape looked like before and what it looked like after. 

http://www.abc.net.au/news/specials/japan-quake-2011/

l. What is your overall impression of tsunami and the vulnerability of coastal regions?

Synonyms: region, area, state, county, zone, district

Japan Population Online Map

 

Article on La Nina weather patterns

A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge.

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