Participating High Schools

Workshops Theme 2 Group D

Japan(Niigata) Niigata Minami High School

School Introduction Video

Presentation Summary

Title Safe Place In The Rias Coast
Survey Introduction The rias coast is a complex terrain that contains mountains, and valley, as well as a raising sea level due to climate changes. While the Rias coast gives us rich fishing grounds, it also experiences abnormally large tsunamis(Sato, 2005). The tsunamis are the largest at the tip of the cape as well as between rock formations (Mizutani, 2005). When disasters happen, evacuation by car is dangerous due to traffic. Also, evacuation on foot is difficult for elderly people because they can't more fast enough. We wanted to find the safest place to evacuate to. Our hypothesis is that "being at the base of the cape is the safest place on the rias coast.
Method A V-shaped rias coast model was created using Styrofoam and installed in an acrylic tank (tsunami experiment device) with an inner diameter of 100cm in length, 10cm in width, and 20cm in height. A plastic cylindrical model was installed at the four points of land on the rias coast (1 cape tip, 2 left cape base, 3 bay base, 4 right cape base). The depth of the water was set 6cm at the deepest part. We inserted a plastic puddle into the water all the way to the bottom of the tank. The paddle was pulled back 10cm and quickly removed, creating a wave. This struck the Styrofoam and the travel distance of the cylindrical model was measured with a digital caliper. We conducted a similar experiment at a depth of 7cm and 8cm. In addition, video was recorded from the top and right side of the tsunami experiment device and the movement of the water was observed in detail.
Results At a water depth of 6cun, the cylindrical model didn't move at the tip of the cape due to the tsunami impact, whereas it did move at the base of the bay, and cape on both sides. At the tip of the cape, the mean distance the cylindrical model moved was 0cm, whereas the base of the bay was 89.14mm. At depth of 7 and 8cm, the cylindrical models didn't move at the tip of the cape due to tsunami impact, whereas the base of the bay and capes all moved beyond the range of measurement. Detailed video observations showed that the water flow was vigorously reached the base of the bay first, and then the water from the base of the bay overflowed onto the base of the cape, moving the cylindrical model.
Issues The hypothesis that the base of the cape is the safest place in the rias coast was not supported. Water reached behind the bay and overflowed to the cape. According to our experiment, the cape tip is the safest place. But, marine topography of some cape tips are shallow and narrow. In this shallow sea area, waves turn toward the cape and increase in size (Mizutani, 2002). Due to the submarine topography, this makes these cape tips dangerous. Most of the rias coast has many sudden underwater drop offs. These drop offs cause the waves to not be affected by the cape. Therefore, cape tips with sudden drop offs are the safest zone.
Action Plan We will research marine topography of the rias coast that have been badly damaged before, and experiment in detail.