Illogical dam policy in Japan
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Illogical dam policy in Japan Yoshiyasu Takefuji1 Received: 28 March 2020 / Accepted: 22 May 2020 © Springer Nature B.V. 2020
Abstract Super typhoon Hagibis on October 12, 2019, in Japan revealed that the current dam control policy has the fatal defect. The current dam policy should be updated for saving humans. Human-induced flood should be avoided by the weather prediction. Keywords Typhoon · Human-induced flood · Weather information · Dam control policy
1 Introduction The Shiroyama Dam is a multi-purpose dam on the main stream Sagami River in Sagamihara, Kanagawa Prefecture in Japan. It was designed to provide flood control and industrial and drinking water to the cities of Yokohama, Kawasaki, Yokosuka, and the Shōnan area where the total capacity is 62,300,000 m3 and catchment area is 1201.3 km2. From October 12, 2019, super typhoon Hagibis has brought a record amount of rain in Japan which was, however, predicted by Japanese weather forecasts (Tonouchi et al. 2019; Natsuaki and Nagai 2020; Islam and Takagi 2020; Shimozono et al. 2020; Tay et al. 2020). The super typhoon had the highest winds (1-min sustained): 260 km/h, causing more than 36 billion USD damage which is the costliest Pacific typhoon in recorded history where 98 died and 7 were missing. The total size of flood areas is more than 185 km2. Although many papers discussed the importance of weather forecast information, this paper addresses the defect of the current illogical water stream dam policy in Japan. The problem of water streams control dam policy in Japan was discovered by the dataset of inflow and outflow, and reservoir level of Shiroyama Dam where the dataset was provided by the Ministry of Land, Infrastructure and Transport in Japan. Note that the lowest reservoir level of Shiroyama Dam is 95 m, while the maximum reservoir level is 125.5 m.
* Yoshiyasu Takefuji [email protected] 1
Faculty of Environment and Information Studies, Keio University, 5322 Endo, Fujisawa 252‑0882, Japan
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Natural Hazards
total_inflow, total_outflow [m3/s]
5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71
Oct.11
Oct.12
total_inflow
Oct.13
hours
total_outflow
Fig. 1 Total inflow and Total outflow of Shiroyama Dam for 72 h from October 11 to October 13, 2019
128 126
reservoir level [m]
124 122 120 118 116 114 112 110 108 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71
hours Fig. 2 Reservoir level of Shiroyama Dam for 72 h from October 11 to October 13, 2019
2 Methodology The open-source dataset of the Ministry of Land, Infrastructure and Transport in Japan is only available in the past 1 week. Therefore, the open-source dataset from October 11 to October 13, 2019, was downloaded during the super typhoon Hagibis period. The dataset includes total inflow, total outflow, and reservoir level of Shiroyama Dam, respectively. Using the dataset, the current dam policy
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