Flood Simulations in Mid-Latitude Agricultural Land Using Regional Current and Future Extreme Weathers

Nobuaki Kimura,Hirohide Kiri,Iwao Kitagawa,Ikuo Yoshinaga,Hidenori Aiki,Sachie Kanada

doi:10.3390/w11112421

Abstract

Recent extreme weather events like the August 2016 flood disaster have significantly affected farmland in mid-latitude regions like the Tokachi River (TR) watershed, the most productive farmland in Japan. The August 2016 flood disaster was caused by multiple typhoons that occurred in the span of two weeks and dealt catastrophic damage to agricultural land. This disaster was the focus of our flood model simulations. For the hydrological model input, the rainfall data with 0.04° grid space and an hourly interval were provided by a regional climate model (RCM) during the period of multiple typhoon occurrences. The high-resolution data can take account of the geographic effects, hardly reproduced by ordinary RCMs. The rainfall data drove a conceptual, distributed rainfall–runoff model, embedded in the integrated flood analysis system. The rainfall–runoff model provided discharges along rivers over the TR watershed. The RCM also provided future rainfall data with pseudo-global warming climate, assuming that the August 2016 disaster could reoccur again in the late 21st century. The future rainfall data were used to conduct a future flood simulation. With bias corrections, current and future flood simulations showed the potential inundated areas along riverbanks based on flood risk levels. The crop field-based agricultural losses in both simulations were estimated. The future cost may be two to three times higher as indicated by slightly higher simulated future discharge peaks in tributaries.

Highlights

Future climate changes may significantly affect the mid-latitude region worldwide according to reports by the Intergovernmental Panel on Climate Change (IPCC) [1,2]
Note that severe overflows occurred in several tributaries in the west and southwest portions of the Tokachi River (TR) watershed such as the Pekerebetsu River and Memuro River
We estimated the possible agricultural damage losses in the southwest portion of the TR watershed, where a severe flood disaster occurred during late August 2016, by using the reproduction-current and future climate data

Summary

Introduction

Future climate changes may significantly affect the mid-latitude region worldwide according to reports by the Intergovernmental Panel on Climate Change (IPCC) [1,2]. The typhoon-affected areas in the North Pacific have been potentially extended to the mid-latitude region. Past studies related to typhoon-impact on flood disasters in the mid-latitude region are relatively few as flood events are rare in the region. Academic reports and articles in English on typhoon-induced flood disasters have seldom been published in the northern East Asian regions such as Northeast China and the northern Korean Peninsula (e.g., Myeong et al [3]). We focused on a mid-latitude area in the North. Hokkaido has recently experienced several severe flood events due to typhoon-included heavy rainfall, typhoons were rare between 1961 and 2016, according to the Japan Meteorological Agency

Methods

Results

Discussion

Conclusion