Why can siltation in a river bed increase flood possibility?

Correct answer: The bed may become shallow and reduce water carrying capacity

Siltation is the accumulation of fine soil, sand or other sediment on the bed of a river. As this material builds up, the channel may become shallower and its capacity to carry flowing water may decrease. During heavy rain or high water flow, the river may then overflow its banks more easily, increasing the possibility of floods. Thus, option A is correct. Siltation does not turn a river into a sea, make water always disappear, or permanently stop floods.

The answer follows from the change in the river channel. A deeper and wider channel can carry more water, while a shallow channel has less available space. If rainfall or upstream flow brings more water than the silt-filled channel can hold, water may spread over nearby land. Siltation is not the only cause of flooding, and its effect depends on local conditions, but it can reduce carrying capacity and raise flood risk. Therefore, the first option gives the accurate explanation.