Review of Research on Irrigation Pond Damage due to Heavy Rain and Related Disaster Prevention Countermeasures in Japan

There are about 170,000 irrigation ponds in Japan (May 2019) that serve a vital role as agricultural water resources in rural areas. However, these ponds are aging and the number of abandoned irrigation ponds has increased due to more farmland being abandoned and the aging of farmers. Many damaged irrigation ponds have been reported after heavy rains and earthquakes. During the past 10 years (2008-2017), 73% of all damaged irrigation ponds were damaged by heavy rainfall. About 64,000 ponds are specified as disaster-prevention-focused irrigation ponds (May 2019), which could pose a significant risk to downstream assets in case of a break. Thus, there has been rapidly growing social concern regarding disaster prevention and mitigation of the threat of such irrigation pond breaks. The prevention of irrigation pond failure due to heavy rain has consequently become a critical research topic. Accordingly, in this paper we review previous research on the damage to irrigation ponds due to heavy rain and the effects of various disaster prevention countermeasures relative to the following: 1) forms of damage and specific causes due to heavy rain; 2) flood analysis in case of a pond break, and flood control measures; and 3) methods of predicting potential damage due to an irrigation pond break.