Geoinformation for Disaster and Risk Management - ISPRS

Command and information chain
The central part of the LFEWS is a communication
chain starting with reading and transmitting rainfall
and river level data upstream to the OC. In case a
threshold is exceeded a warning is issued by the OC
and sent to the four municipalities. From there
different villages are informed, and the message is
passed onto the households. Most steps of the chain
use mobile and landline phones, as well as radio
communication. Households are often informed with
bells or megaphones, which is a simple but robust
method.
Warning colour scheme and communicating
with the people
The LFEWS supported by GTZ merges local
engagement and modern technologies. The rain and
river level gauges are partly automatic, but many of
them are manually read by volunteers from the
community, with data sent by SMS to the OC. While
most steps in the communication chain are covered
by modern devices such as mobile phones or
handheld radios, the final step in the chain is usually
a bell made from a cut gas cylinder. Warnings have
three stages: alert/standby, preparation and
evacuation (Figure 3). Each stage has specific
conditions to be fulfilled before the respective
warning level is issued, and each stage requires a set
of actions from different institutions such as
emergency services or the preparation of evacuation
centres. The Flood Warning Plan is customized for
the OC, the town Disaster Coordinating Councils
(DCC) and the village DCCs. It comes in a colour
scheme with yellow, orange and red for the three
stages. The acoustic warning signals are easily
recognised. One bang with a long break is Level 1,
two bangs with a long break after is Level 2 and
continuous banging is Level 3.
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The potential of low-cost geodata and tools in local
flood early warning
In Binahaan it has been difficult to characterize the
watershed and the flood prone area from locally
available geodata sources. The official topographic
map is 50 years old and little statistical data on the
socio-economic situation are available. Satellite data
can partly fill this gap. The elevation distribution, the
current river bed, and the land cover/land use were
identified using Shuttle Radar Topography Mission
[SRTM] (Kummerow et al., 1998) or Aster Global
Digital Elevation Model [GDEM] (see
http://asterweb.jpl.nasa.gov/gdem.asp), and
SPOT/ASTER optical imagery (e.g. Figure 4).
Figure 3: Colour-coded alerting
scheme used in the LFEWS.