Land conditional analysis for flood disaster combining raster / vector data
Masahiro Setojima, Yukio Akamatsu and Yoko Hirose
Kokusai Kogyo Co. Ltd. 3-6-1, Asahigaoka,
Hino-city, Tokyo 191 Nippon
Tokumaru Kimiaki
Nissho Iwai Corp., 4-5, Akasaka 2-chome,
Minato-ku, Tokyo 107 Nippon
Abstract
As Japan has steep topographic features and rivers are so short, there exist high risks for flood disaster when heavy rain attacks. Thanks to river works, great disasters scarcely happen, however big flood disaster does happen every several years.
The study area is Kokai River where flood covered its basin in August 1986. Combining Lands at TM data and various Geographic Information on the system which enable us to process both RASTER AND VECTOR information, we analyzed Land Conditions for larger area.
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Analyze land conditions for flood covered area in Kokai River basin, using Lands at data and various geographic information regarding land conditions, adjusting them into raster information, and overlaying them each other pixel by pixel.
- Based on the above analysis, extract highly worried area for future flood and collect necessary geographic information.
- Land-conditional analysis operating Raster/Vector Geographic Information System.
We expect that the above methodology would give us a holistic approach for worried areas utilizing limited variety of geographic information.
Introduction
Taiphoon # 10 of 1986 passed through Kanto district (Metropolitan Tokyo included) in the night of 4-5 August 1986, and caused Kokai River flood disaster with enormous damages.
(Fig. 1)
Fig. 1
Landsat data can effectively be used in these cases, which require macroscopic point of view and urgent processing/analysis. While Landsats bring us broad, simultaneous and periodical information, it has a restriction as it depends on earth surface reflection and emission.
If one want to grasp the realities of the flood and use them for prevention of future disaster, correlation among flooded area, land conditions and land use conditions should be considered.
This study tried (1) to grasp realities of flooded area and extract worried areas in flooded zone, utilizing land sat data and several geographic information, then,(2) to collect more detailed information for the above worried areas for the analysis of land conditions for analysis of entire basin for future floods.
Realities of Kokai River Flood Disaster
Heavy rain, caused by a low pressure derived from Taiphoon .# 10, in the night of 4-5 August 1986 made many rivers in Kanto/Tohoku district overflow. Banks of Kokai River collapsed, and broad areas are covered by water, which was confirmed by Landsat TM in the morning of 6 August1986.
Kokai River has another experience of flood in August 1981, construction of river facilities had been imminent. As, at Kokao River, half of its works have not yet completed, flood disaster may occur again in future heavy rain.
We can point out, as the features of this flood, that (1) bank collapsed near artificial structures (i.e. water induction gate) and that (2)flood water flowed into former river channel and rice field.
