contraction and local government makes plans
SABO PLANNING for debris flow,landslide and
SABO
PLANNING,however, depend on past experi-
other natural hazard:
ences and intuition of sk.lled worker. Extraction
of watershed, decision of place and plan for soil
saving dam is very difficult work especially. Be-
sides plan, it 1s more difficult to consider reserve
areas for wild animals,buried cultural
properties,many other natural environment.
In this paper we made GIS system to evaluate
the place where the soil saving dam will constract
in the near future. The system can estimate the
influence of soil saving dam for environmental
conditions by using only digital elevation map.
2. TOPOGRAPHIC FEATURE, LAND-
SLIDE AND DEBRIS FLOW
2.1 Background of the research
We have already been conducted the analysis
of the valley areas with remote sensing data and
thematic map data respectively. 99099101212 We
especially focused the landslide in the mountain-
ous areas on recent years. We used several data
to extract the characteristics of landslide areas.
There are Landsat TM data on the daytime, ther-
mal data in the night time, NVI values from TM
data, geological type ,elevation map and actual
vegetation map.
The reason why we used Landsat TM data in
the daytime and thermal data in the nighttime is
that the underground-water is one of the great
factor on the occurrence of landslide.Then we
considered that the thermal band data has infor-
mation of ground surface temperature which re-
lated to underground-water. '? We next focused
NVI (Normalized Vegetation Index) values from
TM data in landslide areas and non-landslide ar-
eas for pilot district. The following thematic maps
608
were prepared for GIS analysis. They are geo-
logical type map , landslide distribution map ,el-
evation map for calculation of inclination angle
and direction , and vegetation map.
The following subjects were performed by us-
ing GIS. Record oflandslides was classified
under geology and inclination angle of topogra-
phy. We knew relationship between landslide and
geological types. Relation between inclination
angles and landslide areas gives us topographi-
cal characteristics. Satellite data were overlaid
with thematic maps. The actual vegetation map
overlaid with the landslide distribution maps ,
geological maps and other thematic maps.
We have been conducted the procedure men-
tioned above in the pilot area located north dis-
trict of Noto Peninsula in the central of Japan.
These pilot areas are correspond to 6 sheets of
1/25000 scale map. In the pilot area we got the
interested results: (1)We can divide pilot areas
into watershed areas by using GIS. (2)The rivers
made automatically with GIS, which is corre-
spond to the true rivers. (3) GIS is able to ex-
tract small rivers which does not exist on the map.
(4)As the proportion of landslide area increase
band6 CCT data decreases. (5)When the propor-
tion of landslide area over 70 % the shape factor
F increases sharply. (6)We also digitized the ac-
tual vegetation map to overlay with thematic
maps. We find that landslide has relations with
vegetation and trees. As a result we thought that
GIS 1s keyword to estimate the degree of dan-
gerous areas in mountainous district.
2.2 Landslide , debris flow and soil saving
dam
If we want to get more sure results ‚it will need
combination of remote sensing ,thematic map and
GIS techniques.In this paper we focused the soil
saving dam to prevent landslide and debris flow.
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998
