WORLD CIVILIZATION

Detailed explanation-1: -Flood control measures on many large rivers include levees to contain high discharge. When floods do occur, the levees constrain the water, making it move faster and deeper in the main channel instead of spreading out across the floodplain and flowing with a lower average velocity as it would naturally.

Detailed explanation-2: -Flood control channels are large and empty basins which let water flow in and out (except during flooding) or dry channels that run below the street levels of some larger cities, so that if and when a flood occurs, the water will run into these channels, and eventually drain into a river or other body of water.

Detailed explanation-3: -The edge of the flood plain is often marked by a prominent slope known as the bluff line. Levees are raised banks of alluvium formed by the heavier and coarser sediments nearer the river that has been built by successive floods.

Detailed explanation-4: -Portion of the river bed that is occupied by water only in the event of floods.