Evaluation of topographic and water runoff characteristics of mountainous watershed for securing water for domestic use during disasters

Abstract:

Disasters associated with earthquakes and torrential rains result in widespread and prolonged water outages due to damage to water supply facilities and power outages. In order to cope with long-term water outages in times of disaster, it is necessary to consider ways to secure water in accordance with local conditions. The Cabinet Office recommends that each household should stockpile 3 liters of water per person per day for three days. However, securing water for domestic use requires 20 L/person per day, which is more than the amount of drinking water that would be secured as a disaster stockpile or emergency water supply from local governments. As a source of water for domestic use, wells are being constructed in each region. However, in the 2007 Niigata Chuetsu-Oki earthquake, 20% of the wells in Kashiwazaki City were damaged and could not be used. In other words, in addition to wells, it is necessary to consider the use of river runoff and spring water as a source of water for domestic use during disasters in mountainous areas. However, it has been shown that the flow rate of runoff from mountainous areas varies depending on the location and time of year, so it is important to evaluate the stability of the water volume and the place where the necessary amount of water can be secured as a source of water for domestic use during a disaster. Therefore, in this study, we evaluated the flow rate and its distribution in mountainous watersheds in relation to the basin geomorphological characteristics of rivers flowing into the plains where settlements are located from mountainous areas with the same geology in order to secure a source of water for domestic use in times of disaster.