Paper Example. Hiroshima Landslide as a Geo-hazard

Flash flooding and landslides occurred in the early morning of 20th August, 2014 in Hiroshima prefecture located in West Japan. The debris flows and shallow slides were provoked on the northern side of Hiroshima City in Asaminami and Asakita wards. The City experienced a high-intensity rainfall that was more than 200 mm that is a month's equivalent rainfall fell within twenty-four hours. The heavy rain prompted one hundred and seven debris flows and fifty-nine slides that led to seventy-four deaths and forty-four injuries. The landslides destroyed 133 houses and damaged more than 296 homes (Wang, Fawu, et al. para 1).

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Additionally, the landslide forces damaged infrastructures and roads along the mountainous regions. Part of the hills was swept down to people's residence washing away the individuals living there. The landslides caused many deaths because of various reasons such as occurring at night, the slides were muddy, and the floodwater carried down broken trees and debris that smashed down the housed down the hills. Japanese Red Cross Society instantly responded to the hazard, mobilized relief items, and deployed medical personnel in areas affected. It was hard accessing the affected areas by vehicles to offer to relieve because the roads were destroyed. Thus, the red-cross society used helicopters to take rescuers to the affected areas. The geo-hazard led to significant distress to the community that was severely affected.

Causes of Hiroshima Landslides

The landslides were primarily caused by extreme and unusual rainfall events that left the slopes unstable. The torrential rain that occurred within a short duration triggered debris flow in more steep inclines. In the beginning, a thin mass slide was stimulated in weathered rough-grained sandstone that turned into two distinctive kinds of debris flow after flowing down the slopes. The movement behavior of the debris flows was regulated by the debris size, gully's cross-section, and the angle of the hill. Many homes in Japan are built near steep fragile slopes; hence, the place is vulnerable to landslides. Most of the affected people lived in wooden houses that were built in front of the floods exit; thus making them vulnerable.

Debris flows were directed to an area whose elevation was 700m. The mountain region is founded on Hiroshima granite. The lower slope of the mountain contains weathered fine and coarse granite deposits. The mountain is also made of hornfels, which is an intact metamorphic rock that overlays the rough granite. Comparatively, Hiroshima coarse granite weathers more rapidly than hornfels and fine granites; so, the hornfels and fine granite slopes are steeper than coarse granite slopes. The soil in Hiroshima slopes is granitic soil, which wreaths intensely and heavy rainfall leads to its collapse and loss of structure. The fine granitic soil made the debris flow to move in long distances. The drainage and absorbency feature regulated the movement of the debris flow.

Preventive Measures

The climate monitoring system should be practical and accurate. Japan's climate observation system did not predict the rainfall's impacts of stimulating landslides. A monitoring system should have well developed technical equipment for monitoring probable effects and ensure accuracy when interpreting weather behavior. At Hiroshima, the weather department issued a warning in late hours when people were already asleep (Ray-Bennett, Nibedita, and Hideyuki, pg. 17). If the predictions were timely, the number of deaths could be less. A core information system is vital to enable coordination and effective disaster response method.

Organized efforts to evacuate the young and the elderly should be developed to ensure the effective rescue of vulnerable individuals. Timely preparedness and evacuation is essential to avoid the destruction of the landslide disaster (Ge et al., 2014). Early warnings help people evacuate because debris flow is rapid. Human mining errors enhance the promotion of progressive world opinion through the development of disaster preparedness culture and advancement of knowledge on the evacuation process.

The government should identify probable dangerous areas such as unstable slopes and locations prone to landslide to prevent and control hazards. This can be achieved by implementing field investigation and interpreting remote sensing images prior to rain seasons. The results should be used to group the sites either safe, dangerous, and more hazardous for reconstruction and mitigation. For the most dangerous area of flash floods and debris flows, relocation should be recommended (Ge et al., 2014). Additionally, storage dams should be constructed to control debris flow and regulate sediment transportation. Hiroshima had only one dam, which was not enough to reduce debris flow and transport of sediments (Ray-Bennett, Nibedita, and Hideyuki, pg. 20). Also, the channels used by debris flows should be directed to areas of deposition or areas away from residential homes.

Additionally, it is vital to maintain enough distance between the residential locations and debris flow deposition area. Residential houses should be built on higher grounds. In the source location, loose soil should be fixed through natural vegetation recovery by planting trees. Soil should be conserved by inhibiting human activities such as deforestation, agricultural activities, and construction of buildings, which provoke soil erosion (Ge et al., 2014). Taking care of soil at the source minimizes the chances of landslides and stops initiation or formation of slope debris flow.

Work Cited

Ge, Yonggang, Jianqiang Zhang, and Xiaojun Guo. "Characteristics and prevention of the debris flow following the Wenchuan Earthquake in Jushui River Basin, an County, China." Journal of earthquakes 2014 (2014). http://dx.doi.org/10.1155/2014/519865

Ray-Bennett, Nibedita S., and Hideyuki Shiroshita. "Disasters, Deaths and the Sendai Framework's Target One: A Case of Systems Failure in Hiroshima Landslide 2014, Japan." https://www.unisdr.org/files/66627_f424finalnibeditas.raybennettdisast.pdf

Wang, Fawu, et al. "Preliminary investigation of the 20th August 2014 debris flows triggered by a severe rainstorm in Hiroshima City, Japan." Geoenvironmental Disasters, 2.1 (2015): 17. https://link.springer.com/article/10.1186/s40677-015-0025-6#Abs1