Changes in Urban Indices after the Great Fire Disaster Recovery in Itoigawa, Niigata

抄録

A huge fire occurred on December 22, 2016 in Itoigawa, Niigata. Records show that instantaneous wind speeds reached 27.2 m/s, whereas 120 houses were burnt down, 147 houses were damaged, and an area of approximately 4 ha was affected. The city has been promoting the recovery of infrastructure from September 2017. In this study, the recovery was evaluated based on the Landsat-8 time series data by using urban indices. By comparing the indices in damaged and non-damaged areas, the authors investigated the relationship between the recovery status and index values. The urban index (UI), built-up area (BA) and Grain Size Index (GSI) were used in this study. The UI is calculated based on the difference/sum of bands 7 and 5. The BA is determined by the difference between the Normalized Difference Built-up Index (NDBI) and the Normalized Difference Vegetation Index (NDVI), which are calculated by the difference/sum of bands 6 and 5, and by the difference/sum of bands 5 and 4, respectively. Changes in each index in the damaged and non-damaged areas were recognized from the Landsat data collected for two years. However, sufficient time is required to initiate a restoration plan, and, therefore, the present status is limited to the planning stage. This is one of the reasons why changes in the indices were not so clearly visible. Moreover, as indices are influenced by seasonality, it should be compared between the images observed during the same season.