GEOLOGY

Detailed explanation-1: -Floods are the most frequent type of natural disaster and occur when an overflow of water submerges land that is usually dry. Floods are often caused by heavy rainfall, rapid snowmelt or a storm surge from a tropical cyclone or tsunami in coastal areas.

Detailed explanation-2: -It is necessary to distinguish between the following main types of dam-related hazards: Natural– strong earthquakes, excess precipitation or snow melt, which cause water overtopping, or landslide occurrence, which can damage the system due to rocks falling or sliding into the reservoir.

Detailed explanation-3: -During heavy rainfall, the dam stops the water from overflowing in the particular area. When the height of the dam is low, the gates of the dam opens up. So, the excess water flows into the area of livelihood. This causes flooding.

Detailed explanation-4: -In an undammed river, the flood water rises over a period of time, which allows people to respond. Moreover, due to the dam the contours of the riverbed, the flow of the river downstream and even the floodplains change.