1953 North Kyushu flood

The 1953 North Kyushu flood was a flood which hit Northern Kyushu, Japan in June 1953. The flood was caused by cloudbursts and prolonged rain from the Meiyu rain front which dropped 1,000 mm of rain over Mount Aso and Mount Hiko; this downpour resulted in the overflow of many of the surrounding rivers, such as the Chikugo River. The flood was a major disaster with 1,001 people dead or missing, 450,000 houses flooded, about 1 million people affected. Due to the severity of the disaster, flood control measures along rivers in Northern Kyushu were fundamentally revised, with many of the changes still in place; the flood was not given an official name by the Japan Meteorological Agency which has resulted in it being referred to differently in a variety of sources. In Kumamoto Prefecture, Shirakawa Great Flood or 6.26 Flood are used. In Kitakyushu city, they tend to use North Kyushu Great Flood. In this article, 1953 North Kyushu Flood is used, based on the area of the flood; the flood was the result of a combination of meteorological and geological factors that contributed to large amounts of precipitation as well as topographical features which exacerbated the effects of the precipitation.

Early June the Meiyu rain front had come to a standstill over north-central Kyushu, raining over the city of Fukuoka and Nagasaki at the start before latter bringing rains over Kumamoto. The front moved south over Amami Ōshima before fluctuating between Amami Ōshima and Yakushima. Meanwhile from the south, the Pacific High in the area around the Philippines began to grow in strength and push the rain front into the Tsushima Strait. At the same time a mobile anticyclone from China began pushing the rain front back towards Yakushima. Trapped between these two competing forces the rain front became stabilized over Mount Aso around June 23. Moist, warm air from the high pressure areas stimulated the rain front while low pressure waves that would have passed through were instead redirected through the Tsushima Strait. Working in tandem these meteorological conditions generated the cloudbursts and prolonged rain that led to the unprecedented amount of precipitation over northern Kyushu. In addition to the heavy precipitation, geographical factors contributed to and exacerbated the flood.

Mount Aso, one of the largest active volcanoes in the world, has produced throughout the surrounding area a lava cap of andesite, poorly permeable to water. Additionally, deforestation during and after the Second Would War had decreased the local water retention capacity; these factors combined to allow the precipitation to flow unimpeded into nearby waterways which subsequently exceeded their capacities. Furthermore, just two months prior on April 27, Mt. Aso had erupted and deposited 5.16 metric tons of ash which combined with the rain water to produce a debris flow. Topographically, the rivers in northern Kyushu tend to follow steep grades which cause them to flow downstream. Additionally the river systems in the area have larger drainage basins upstream than middle- and downstream with the Shirakawa River and Chikugo River having drainage basin ratios of 80% and 70% between their upstream and downstream systems; these topographical features resulted in the upstream systems accumulating and transporting water in amounts that the lower stream systems couldn’t handle.

In Kumamoto Prefecture, the central river Shirakawa flooded most and people remember it by the name of 6.26 Suigai. The factors of the 6.26 flood were: heavy rain in the Aso district, the rainfall reached 888.4 mm in 5 days, another factor being the soil of the areas. A similar event was seen in 1993 Kagoshima Heavy Rain.. On April 27, Mount Aso erupted and a great amount of volcanic ash which fell was mixed with rain; the third factor was the Kumamoto city. These factors worsened the damage of the flood. 70% of the Kumamoto city was flooded, except the Kyomachi Hills and Kengun area. The central areas of Kumamoto City were 2.5 meters to 3 meters deep in muddy water. 15 bridges out of 17 in the city were carried away except Choroku Bridge. Kokaibashi was carried away with 40 inhabitants; the disposal of 60,000,000,000 tons of muddy soil presented big problems. The Kumamoto city gave subsidies to clean up the streets. A house for the aged was destroyed and 52 people were killed; the damage amounted to 17,300,000,000 yen Even in the southern part of Aso gun, the dead and missing amounted to 66.

Shirakawa Suigai in Japanese The Chikugo River flows through Kumamoto, Oita and Saga prefectures in Japan. With a total length of 143 kilometres, it is the longest river on Kyushu, it flows from empties into the Ariake Sea. The river is important to industry, with twenty electrical power plants located along its banks, as well as the major city of Kurume in Fukuoka Prefecture. 147 people were killed in the areas of Chikugo River. 80 percent of


Kräppladiket is one of the four inflow rivers of Lake Magelungen in southern Stockholm, Sweden. It empties into the lake in its northern end together with Magelungsdiket and Norrån while Djupån joins the lake on its southern end. In contrast to Magelungsdiket, Kräppladiket was not affected by the construction of the south-western suburbs in the early 1950s, but important part of the ditch was however guided through culverts limiting the open stream to the 1,4 km passing through the Rågsved Open-air Area south of Rågsved. A bit less than 50 per cent of the catchment area is occupied by green spaces; the upper reach of the ditch is thus affected by low levels of phosphorus and nitrogen, while samples by the lower reach, next to the Snösätra industrial area, showed a presence of high levels of metals. The mouth of Kräppladiket is located in a Reed bed and no defined outflow exists. In 2006 works were started to create a small stormwater dam to purify the water of the ditch before it reaches Lake Magelungen.

The initiative will attract birds and plants. The initiative is part of a project aiming at making Magelungen accessible to angling and canoeing by dredging selected portions of it. Geography of Stockholm Rivers of Sweden "Vattenprogram för Stockholm 2000 - Magelungen". Stockholm vatten. Archived from the original on 2007-09-27. Retrieved 2007-06-08. "Damm vid Kräppladiket". City of Stockholm. 2005-06-20. Retrieved 2007-06-09. "66 Magelungen och Kräppladiket". City of Stockholm - Miljömiljarden. 2005-04-14. Archived from the original on 2007-09-28. Retrieved 2007-06-09. "Kräppladiket". Stockholm vatten. 2007-02-23. Archived from the original on 2007-09-27. Retrieved 2007-06-09