Causes of sudden water level rises :
- Even in fine weather :
- A water intake may suddenly close (obstruction, technical failure, saturation due to excessive water input) : the water -
normally channelled into a tunnel - brutally resumes its former course in the river bed.
- A lake that is almost full may overflow if a glacier pocket breaks upstream or if there is an unscheduled stop of the
pumping or turbine station fed by the lake.
- In case of precipitation :
-
A water intake
purge may start and brutally increase the volume of streams already swollen by rains.
- Also, following droughts, objects may hinder water outflow and form natural dams that, if they suddenly collapse,
abruptly release a large water mass into the river bed.
- When precipitation ceases :
-
The basins and water reservoirs are often choked with gravel, branches etc.: a water intake
purge may then start causing a sudden rise in the water level downstream.
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