The contrast of the warm sea with cold air bags arriving in autumn (that being lighter rises rapidly, creating a big storm, which forms very heavy rains of up to 500 liters per square meter (as in Gandia the year 1987 ) and winds of over 140 kilometers per hour. addition resulting storm surge can raise the sea level one meter, with waves 4 and 5 meters high.
The destructive power of the cold drop, increases considerably when forest areas are destroyed (by fire, uncontrolled urbanization, deforestation, ...), since it increase greater temperature contrasts, not retain water from the rain, loses all the fertile land (not to be fixed by trees) that is driven by floods making them even more dangerous.
Moreover heavy rains are usually in short periods of time, raining more in a few hours than the rest of the year in the area.
picture of yesterday in Elche (Alicante), taken from the digital edition of the newspaper "La informacion" from Alicante