Typhoon Neoguri

Super-typhoon Neoguri was just one of several large scale storm systems to develop in 2014. It was similar in size and characteristics to Hurricane Katrina that was discussed in the previous module. Figure 5.2 (courtesy of Ms. Katona Miller- Shippensburg University alum.), shows the conditions of the storm during its onset. The storm was fierce and led to intensive rain, high waves, and strong coastal currents, which, in addition to a strong storm surge, battered the coastline of Okinawa, Japan. Despite its immense size and intense winds, Neoguri produced significantly less damage and far fewer human losses than Hurricane Katrina. Why? The reality is that Japan sits in a geologic and geographic location that is susceptible to these large scale storms like the Gulf Coast, but which is also prone to tsunamis that have routinely devastated the coastlines of Japan and other Pacific island nations for 1000s of years. The very fact that the coastline is impacted so frequently has led to numerous rules and regulations to engineer the shoreline and coastal buildings to reduce the impact from such powerful coastal catastrophes.

In the Gulf Coast, the main engineering solution in a very different geologic setting has been the use of levees which were built to primarily reduce flooding in a low-lying city that exists primarily below sea level. These levees were engineered to different standards and for different purposes than those in Japan. More on this later in the course. Nevertheless, in Japan, the combination of breakwaters, like that shown in Figure 5.2, concrete seawalls, and block revetment structures on the shoreline (Figure 5.3) are among the engineering solutions utilized in Japan to protect land and property from intensive waves and strong erosive surges on a coastline that has significant topographic relief. Unfortunately, engineering the coastline also comes at a cost, i.e., the loss of the recreational shoreline and beach systems that are often removed or eroded as a consequence of building on the shore.

In this module, we will explore the science of coastal catastrophes in more detail. We will start with Katrina.

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Figure 5.2: Sunset Beach, Okinawa Japan. Photo taken by Katona Miller (Shippensburg University alumna) immediately following Typhoon Neoguri that crossed Okinawa Island on July 6, 2014. Neoguri was one of the largest typhoons to hit Japan in several decades. Sustained winds exceeded 100 miles per hour with gusts over 130 miles per hour reported as the storm came ashore. 600,000 people in Japan were advised to evacuate their homes, especially those located on or near the shoreline where 46 foot high waves and significant storm surge was predicted. Katona's image shows evidence of erosion in front of the seawall built to help protect the highway from storm waves along the shoreline.
Credit: Katona Miller

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Figure 5.3: Another view of the shoreline of Sunset Beach showing a number of breakwaters built parallel to the shoreline. These structures were engineered to reduce wave energy and help protect the beach behind them. Neoguri's storm waves inundated the coast and scoured beaches and stirred up sediment that muddied the pristine water for hours after the storm.
Credit: Katona Miller

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Figure 5.4: Constructed "tetrapod" seawall at Okinawa Japan. As Japan and other island nations in the western Pacific experience numerous coastal catastrophes, whether from storms or tsunamis, they have implemented a large number of coastal engineering projects to help reduce the severity of impacts of these events. This seawall in Okinawa took an intensive beating from storm waves and helped reduce erosion of the shoreline beyond the constructed wall.
Credit: Katona Miller

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Figure 5.5: View out to sea showing the exposed tidal flat during the low tide that occurred as the storm passed to the north. Storm waves are still observed crashing in the distance. In the foreground is a wide variety of debris eroded and deposited during the storm.
Credit: Katona Miller

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Figure 5.6: Storm deposit composed of fragments of marine organisms including fire coral and red calcareous algae. Many of these organisms were already dead and part of the sediment deposited on the sea floor, but waves from the typhoon eroded the fragments and redeposited them as a new sediment layer during the storm. The large clast sizes, and absence of fine-grained sediments, records how high the energy was during the storm.
Credit: Katona Miller

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Figure 5.7: View to the northwest of Sunset Beach area as Typhoon Neoguri moved to the north of the island. Muddy water in the foreground is from upland stream erosion from heavy rainfall. In the background, high waves are still crashing on the shoreline where rock revetments and breakwaters take the brunt of the energy from the high waves.
Credit: Katona Miller

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For more information about Typhoon Neoguri visit these websites

• NASA: Neoguri (Northwestern Pacific Ocean)
  
• NASA: Typhoon Neoguri images