RECOGNITION OF HYDROLOGICAL DATA OF THE ASHIDA RIVER BASIN AND CONSIDERATION TO FLOOD-DAMAGES IN LOWER BASIN BY INTENSIVE RAIN AT JULY 2018

Abstract

 The Ashida River basin was suffered by intensive storm named as “West Japan Heavy Rain” from July the day 5th to 8th, 2018. The contents of this paper are constructed to two different aims. At the first part, the hydrological data such as rainfull, riverflow and dam pondage during the intensive storm were estimated. The rainfall intensity of every 1 hour and the cumulative values of rainfall at 4 observatorys in lower basin of the river were especially estimated. Considering to the rainfall depth of Fukuyama observatory, one day (187.0mm), two days (282.0mm) and three days (373.5mm) records were severally the past highest values. The probable rainfall intensity value of one day (the day 6th) was calculated about 1/130 years. The riverwater level and volume at Yamate observatory in the testfield area were the past highest values and exceeded the dangerous values during about 1 hour. At the secondary part, the 3-dimensional survey data used by UAV were analyzed in comparison with June and August. The damage of rivercourse way and shape over the test-filed area was made clear. And then from the viewpoint of vegetation, the damage due to intensive storm at July was made clear based on NDVI treatment.