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NOAQ BW102 1.0 201201
7. Flash flooding
The boxwall can also be used in flash flooding, when water is running fast over the streets.
When this happens the most obvious measure is to protect low entrances and vulnerable
objects by redirecting the water flow toward areas where flooding will cause less damage.
A similar situation can occur when snow is melting, and the water tries to take unacceptable
routes. As for the use in calm water, the boxwall should only be used on firm and even
surfaces.
If water is already running fast at the place of the intended action, the first measure would
be to place a number of boxes in the water flow, to break down the speed of it and reduce its
power. Put the boxes close to each other, facing upstream, but do not try to connect them.
They will be anchored directly by the weight of the water entering upon them.
Behind this protective row of boxes a continuous boxwall may then be assembled. When the
boxwall is completed, the front row of boxes can be removed.
This way the boxwall can be used to lead away watermasses in a controlled manner down
the streets, hereby reducing water levels and flood problems upstream. The boxwall does
not need to be in the shape of one continuous barrier, a number of short boxwalls can be
deployed just at the spots where the water needs to be redirected. For some streches short
overlapping sections of boxwall may also be an easier alternative to one long single barrier.
To divert the water off a street the boxwall may be deployed diagonally. The angle chosen,
in relation to the direction of the current, depends on the amount of water and its speed.
