Olive tree and the wind

Olive tree in Tipasa, illustrating the effect of the dominant wind from
the north. The fact that the Oued Bellah bridge is in a valley that
funnels the strong northerly winds which are common in this area, means
that any instability can have lead to collapse by earthquake or by an
exceptional storm. In any case, we can attribute the failure of this
bridge to human (Roman) error.