Flash floods are often associated with isolated and localised intense rainfall. But Flash floods may result from the failure of a dam or the sudden breack-up of ice jam. Flash floods in urban areas is serios problem too.
The change in the climate has increased the floods of this type. Such floods are harder to predict, they can occur in dry places where there is no running river. Such floods can prove very dangerous since they start suddenly and develop very fast.
In the case of flash floods the reaction is mostly hindered by the very short time between their origination /continuous heavy rainfall/ and the reaching of the water peak in short time.
The flash flood is characterized by the fast increase in the water level, the high speed and large quantity of debris in water, giving the flood a high destructive power. The main factors causing the origination of a flash flood are: the intensive and continuous rainfall and the steep water sheds.
In certain regions the flash floods often result from isolated high-speed local rainfalls, rendering the warning and protection of the population a very difficult task. In other regions such floods occur annually in one and the same river, where warning the population is possible, but advance organization is needed, since the reaction time is quite short. Flash floods are capable of tearing out trees, undermining buildings and bridges and scouping new chanels.
Mountain torrents occur at intensive rains for long and short time in the mountain areas. This happens because the river bed slop is big, the water runs fast and carry with itself dispersive mass.
The improvement of the forecast systems already gives opportunity for announcement and information of the population at the threatened zones in most cases.