Research Trends and Results

Research on Technology for Real-time Flood
Monitoring
TAKEUCHI Yoshinori, Researcher; ONAMI Hiroyuki, Researcher; ITO Hiroyuki, HeadFlood Disaster Prevention Division, Research Center for Disaster Management
Keywords: flood monitoring, real time, private-sector probe data, big data
1. Trends and needs for flood monitoring technology
In the event of a flood due to overflow from a river,etc., information from real-time monitoring of actual
conditions, as well as flood prediction, is very important
for accurate evacuation guidance, flood control measures,prompt recovery, etc. In 2013, many places in Japansuffered damage from flooding as seen in theYamaguchi-Shimane Heavy Rain (July) and Typhoon No.
18 (Sep.). It is, therefore, urgently required to develop
technology for monitoring floods in real-time in order toreduce damage.
In the development of flood monitoring technology,
various measures have been previously studied and someof them have actually been developed, including the useof CCTV, installation of flood detection sensors andflood level gauges, and a system for transmitting andreceiving flood observation information using mobilephone lines or existing optical fibers. However, all ofthese technologies have issues, including how to manage
investment and maintenance costs, ease of introduction,
tracing of time changes in flooded area, and detection offlooded areas. This paper reports on a study on detecting
flooded areas using private-sector probe data without new
observation equipment.
2. Study on the feasibility of using probe data
(1) Characteristics and advantages in using
private-sector probe data
Private-sector probe data refers to automotive traffic
information obtained by private-sector companies, which
is one of so-called “big data.” All of the approaches
already discussed directly observe flood water, but thisstudy takes an indirect approach focused on themovement of goods susceptible to the effects of flooding.
This approach uses technology that was developed toprovide information on traffic congestion, etc. undernormal conditions, and has the potential to monitor theexpansion of flooded areas to a high degree of accuracy
in urban areas where roads are densely arranged.

(2) Availability of private-sector probe data
In this study, spatiotemporal changes in the travel
speed on each route obtained from probe data were
examined using speed data as an indicator of automotive
traffic characteristics, covering the areas flooded by theheavy rains that hit Nagoya City in September 2013
(originally estimated by integrating results of hearings
from related organizations, SNS information, etc.) andsurrounding areas. The figure shows an example of thestudy results. The right image shows traffic in the 17:00- 19:00 time period when heavy rain or flooding occurred,
while the left image shows the traffic in the same time
period under normal conditions. Looking at the travel
speed (time average) under normal conditions andflooding, a clear trend of decline is recognized in theflooded areas (estimated) and surrounding areas. With
this data, it is found that traffic conditions are susceptible
to flooding, etc. and those conditions are reflected in
private-sector probe data.
3. Conclusions
The potential for using private-sector probe data for flood
monitoring technology was obtained from this study. We willcontinue to examine ways to upgrade indicators, etc. byconsidering the effect of impassable cars at certain points I orderto enhance the reliable of flood monitoring.
Legends

Legends

No less than 40 km/h
Less than 40 km/h

No less than 40 km/h
Less than 40 km/h

Less than 20 km/h

Less than 20 km/h

Less than 10 km/h

Less than 10 km/h

Flooded area (estimated)

Flooded area (estimated)

NagoyaStation

NagoyaStationFigure: Comparison of Travel Speed under Normal
Conditions (left) and Flooding (right)