Flash floods

Flash floods, which have taken many lives and caused great property damage, are local floods of great volume and short duration. A flash flood generally results from a torrential rain or 'cloudburst' on a relatively small drainage area. Cloudbursts, associated with severe thunderstorms, take place mostly in the summer. Violent thunderstorms or cloudbursts usually develop in a short time and produce floods on relatively small and widely dispersed streams. Runoff from intense rainfalls result in high flood waves that can destroy roads, bridges, homes, buildings, and other community developments. Discharges quickly reach a maximum and diminish almost as rapidly. Flood flows frequently contain large concentrations of sediment and debris collected as they sweep channels clean. Flash floods can also result from the failure of a dam or from the sudden breakup of an ice jam. Each can cause the release of a large volume of flow in a short time.

Flash floods can take place in almost any area but they are particularly common in mountainous areas and desert regions. They are a potential source of destruction and a threat to public safety in areas where the terrain is steep, surface runoff rates are high, streams flow in narrow canyons, and severe thunderstorms prevail.

Heavy rains in June 1998 brought about the worst floods in the history of Slovakia, changing otherwise quiet rivers in eastern part of the country into a lethal force. The tragic results were 63 dead, over 3,000 people evacuated from their homes, and two thousand houses destroyed. Since shacks are incomparably more vulnerable to natural disasters than proper houses, this flash flood hit the Gypsy settlement near the community of Jarovnice the hardest, and the highest number of casualties occurred there. Jarovnice is one of the largest and most backward of the Romany settlements in Slovakia. Almost four thousand Roma live in unbearable living conditions there, most of them without work and illiterate. The otherwise harmless rain-swollen Mala Svinka brook claimed at least 44 children and 16 adults.

Deforestation can, in the short-term, lead to increased run-off and soil erosion, mudslides and flash flooding. Poor forest management has exacerbated flash floods across the world, such as those witnessed in the Philippines which killed more than 5 000 people in 1991, and the mudslides in southern Italy in 1998.