Question

A flash flood is a flood that_________
A. Is caused by heavy flooding of a river
B. Occurs in urban areas
C. Occurs suddenly and unexpectedly and for a short duration
D. Is caused by the blocking of drains

Answer 1

Hint:Flash floods are named so due to the speed at which it occurs. It can occur in areas regardless of whether it is rural or urban.

Complete answer:
Floods are defined as an overflow of water onto normally dry land. Depending on the causes of flooding as well as the structure of the area, flooding may last days or weeks. The causes of flooding are heavy rainfall, overflowing of water from rivers or lakes, failure of proper drainage systems or structures like dams getting damaged. Flash floods are different from other types of floods because of the speed at which rate of flooding occurs. Let us now see which of the following is the reason for flash floods-

A. Floods are often caused by heavy flooding of a river. But this kind of flooding is not flash floods. Rivers often flood when water level rises above their banks gradually, usually in the monsoon season. This is a regular process which over the years builds silt plains. Thus, this is not the correct option.
B. Floods can occur in any area. Floods occurring in Urban areas are not separately classified as any unique or distinct type. In other words, flash floods are not defined based on where it occurs. This is an incorrect option.
C. As noted above, flash floods are so named because of the speed in which the flood occurs. It happens without any warning and within a short time the area gets flooded heavily. So it is sudden and unexpected. Therefore, this is the correct answer.
D. Floods caused by blocking of drains are a very common cause of urban area flooding. But it is not a cause for flash floods. It can, however, be a contributing factor for severe floods. Therefore, it is not a correct option.

Hence the correct answer is option C.

Note:Flash floods are caused by excessive rainfall occurring in a short period of time.
The heavy water flow can rip through river beds, canyons, or urban settlements, sweeping everything before them. It is more common in areas with relatively small catchment areas with little or no permanent path for flow of water. In rare cases, flash floods occur in the absence of rainfall due to causes like failure of dams or levees.