transmission, for a state-of-the-art review.
future are discussed.

In addition, issues expected to arise in theHISTORY OF HEAVY RAINFALL DISASTER INFORMATION IN JAPAN
Progress of Rainfall Observation Network
Modern rainfall observation in Japan started in the 1870s. Initially, there weremainly weather offices; after that, the number of cooperative observatories increased.
In 1910, there were about 1200 observatories all over Japan. The data collected bythese observatories was administered by the Central Meteorological Observatory (thepresent JMA). The present observatory network, run by the Japan Meteorological
Agency (JMA), has more than 1300 observatories.
Since the 1960s, the JMA started automatic observation and real time datacollecting in the JMA cooperative observatories.
The AMeDAS (AutomatedMeteorological Data Acquisition System) is the final product of such efforts by the JMA.
It was developed in the 1970s, and completed in 1978. It has about 1320 observatories
all over Japan, with one station per 17 * 17 km grid square (Figs. 1 and 2).
Temperature, precipitation, wind, and the number of hours of sunshine are observed
every hour. The observation data is collected through the telephone line in real time.
The AMeDAS is the most popular weather observation network in Japan. About 20
years has passed since the AMeDAS was completed, and, therefore, this network has
been used to obtain climatic statistics such as normal values.

Fig.1 Distribution map of AMeDAS observatories

Fig.2 AMeDAS observatory

In the 1990s, the prefectural precipitation observatories were improved. In 1995,
there were 1321 observatories run by the JMA, 2886 observatories run by Ministry ofConstruction (the present Ministry of Land Infrastructure and Transportation), and2199 observatories run by prefectures (Hydrology Study Group, Ministry ofConstruction, 1996). The number of prefectural observatories has recently been
increasing. For example, Nagano Prefecture had 97 observatories in 1991, but had
156 (one observatory per 8.3 * 8.3 km grid square) in 1999. In addition, observationand data collection were automated in the observatories during the past 10 years.
Practical Use of WWW for Heavy Rainfall Disaster Information
The number of Internet users in Japan was estimated to be 32 million in February
2001, and the percentage of households using the Internet was estimated to be 46.5%(Association of Internet, 2001). However, the history of Internet use in Japan is short.
The first use of the Internet for disaster information was in around 1995, when the
Hanshin-Awaji earthquake occurred. Initially, citizens and private sector groups usedvarious Internet sites for the exchange of relief information. In 1996, private weather
companies started to supply weather information, e.g., weather forecast, precipitation
observation data, weather radar data, etc., through Internet.
The first full-fledged use of the Internet by the government sector was at the timeof the Tochigi and Fukushima heavy rainfall disaster in August, 1998 (Ushiyama,1999). Local governments such as the Tochigi prefectural office, the Fukushima
prefectural office, and the Kouriyama city office, which were heavy damage area,
disseminated information on their homepages shortly after the disaster. By 2000,
almost all central government, prefecture, city, town and village offices had their own
homepages. Several governmental homepage played an active part in transformationof disaster information at the time of Tokai heavy rainfall disaster in September 2000
(Fig. 3).

Fig. 3 The active Web page about heavy rainfall event in September 2000 by Gifu Prefecture.

On the other hand, it is of note that several public offices did not use their
homepages for disaster information dissemination, as pointed out in a newspaper
article on the disaster (Fig. 4, Inoue et al., 2001). Namely, we may say that homepage
is becoming more widely used to provide disaster information.

Fig.4 The article of Asahi Newspaper in September 14, 2000

Until around 1999, most disaster information homepages were opened temporallyafter the disaster. These homepages mainly contained damage reports and relief
information.
Since 2000, the number of permanent homepages for disaster
information has been increasing (e.g., Fig.3). In 2001, the types of disaster
information homepage existing on the Internet consisted of:1) The Weather forecast
2) Heavy rainfall warnings and advisories
3) Meteorological satellite image data4) Weather radar rainfall data
5) AMeDAS observatories precipitation data
6) Precipitation and river water level, reported by the Ministry of Land Infrastructureand Transportation or the local prefecture7) Short range forecasting precipitation
8) Disaster damage statistics and the actions being taken by the government sector
9) Relief information offered by voluntary groups and the like.
10) Hazard maps provided by government sectors (dangerous zones, evacuation zones,
hazard simulation data, etc.)
11) Disaster research reports and basic knowledge about the disaster, provided bygovernment sectors or by scientists.

Fig.5 Example of disaster information homepages

Top: Weather warning and advisory (Japan Weather Association, http://tenki.jp/), Bottom: Disasterdamage statistics and the action of government sector (Fire and Disaster Management Agency,
http://www.fdma.go.jp/html/infor/index.html)

Fig.6 AMeDAS observatories precipitation data
Real Time Heavy Rainfall Display System (created by Ushiyama, http://www.disaster-i.net/rain/)Practical Use of Internet Accessible Cellular Phone
In Japan, the use of cellular phones accessible to the Internet has spread in
advance of the rest of the world. The most popular system is the "i-mode" introduced
by NTT DoCoMo in February, 1999 (Fig. 7). The i-mode can send and receive Internet
electric mail (e-mails); and can also browse HTML files. As of February 2001, thenumber of Internet users was 32,636,000. The percentage of households using theInternet in Japan 2001 was estimated to be 46.5%, while that of households using
cellular phones is estimated to be 28.4% (Internet Association, 2001). The number ofusers of Internet accessible cellular phones is increasing today.
Systems like the "i-mode" are expected to be useful tools for collecting andexchanging information at the time of a disaster, though they require time to process
image data and have limitations on the contents (or characters) they can display on theliquid crystal display of a cellular phone. One reason for the expectation that thesetypes of systems will be used in disasters is that "i-mode" phones can be used to accessthe Internet without personal computers, PDA, etc. "i-mode" accessible information isincreasing. Already, the "i-mode" can browse various kinds of disaster information, as
shown in the preceding paragraph.

Fig.7 Image of "i-mode" phone
The top page of the Real Time Heavy Rainfall Display System (i-mode version)

Normal e-mail system
InternetDisaster warning e-mailLAN, Modem"i-mode" e-mail system
Fig.8 The "i-mode" and normal e-mail system

PCAnother reason is that "i-mode" phones can automatically receive e-mail (Fig.8). In
normal e-mail systems, a user must access an e-mail server first; but the "i-mode"system can notify the user that e-mails have been received at any time. Therefore, the"i-mode" phones can automatically receive not only precipitation data but also somedisaster warning information during times of heavy rainfall. Most pagers, which arecalled "Pocket Bell" in Japan, can be used similarly, because the pagers are able toreceive Internet e-mails.

CONCLUSIONS
The recent changes in heavy rainfall disaster information dissemination in Japan aresummarized as follows:
1) The high density automated meteorological observatories network of JMA(AMeDAS) was completed in 1979. Recently, the data obtained through this network
has been widely used.
2) After the 1990s, local (prefectural) governments improved their rainfall
observatories networks. Many raingauges have been made automatic. As thenumber of observatories was increased, the raingauge density in Japan is now one
raingauge per several-km square.
3) Since the late 1990s, Internet usage has progressed quickly, and has become widelyused in the public and private sector. The first full-fledged Internet usage for rainfall
disaster by governmental sectors was at the time of the heavy rainfall disaster inAugust 1998. Since around 2000, many governmental home pages continuously
provide information on disasters for the general public in Japan.
4) Since 1999 in Japan, the use of Internet accessible cellular phones has become
widespread, in advance of the rest of the world. Such phones are expected to be usefultools for information collection and exchange at the time of disaster, because they areable to receive warnings at the time of heavy rainfalls, and can notify the user whene-mails have been received.
The quantity and quality of heavy rainfall disaster information in Japan has
made remarkable progress during the past 10 years. In the USA, the "Tone Alert
Radio" or "Weather Radio" a radio type weather or disaster information transmittancesystem, was popularized before the Internet (J. Sorensen, 2000). However, Japannever had such a system, and the Japanese have little know-how about disaster
information usage. Ushiyama (1999) indicated that many people did not understandrainfall information well, including the methods used in rainfall observation and theunit of measurement used to measure rainfall (the fact that it is measured in mm). It
is important to educate people by not only providing simple data, but also by explaining
the information supplied.
It is well known that telephone line congestion often occurs at the time ofdisasters. In Japan, most Internet users access the Internet through the telephoneline. Therefore, it was presumed that many Internet users were not able to access theInternet at the time of a disaster. Nakamura (2001) reported that this occurred
during the Geiyo Earthquake in March, 2001.
These are groundbreaking years in terms of the Internet disaster information age
in Japan. It is necessary to investigate how to use the information at the time ofdisaster, and to suggest methods on the effective use of the information technology
available.
REFERENCES
Hydrology Study Group, Ministry of Construction (1996) Hydrological Observation,
Japan Construction Engineer's Association, p.12.
Internet Association (Ed.) (2001) Internet White Paper 2001, Impress Inc. (inJapanese), p.32-37.
Inoue, K., Ushiyama, M., Ishigaki, T., Toda, K. and Kuriyama, K. (2001) On Heavy
Rainfall Disaster in Tokai District in September 2000, Annuals of the Disaster

Prevention Research Institute Kyoto University, No.44 B-2, 277-287.
Sorensen, J., H. (2000) Hazard warning system: Review of 20 years of progress,
Natural Hazards Review, Vol.1, No.2, 119-125.
Ushiyama, M. (1999) A survey of understanding about precipitation information,
Proceedings of First Annual Meeting of Japan Society for Disaster Information,
October 1999, p.143-146 (in Japanese).
Nakamura, I. (2001) Geayo Earthquake and problems in communication media,
Proceedings of Third Annual Meeting of Japan Society for Disaster Information,
November 2001, p.72-78 (in Japanese).