Which of the following is a method to prevent floods?

Levees, winding streams and efficient sewage systems are all methods that help prevent or reduce floods.

Levees are raised embankments that keep rising river water within its channel.

Winding, meandering streams slow the flow and lower the chance of sudden overflow.

Efficient sewage and drainage systems carry away excess water and prevent urban waterlogging.

Since each measure genuinely helps, all of the above is the fitting answer.

Combining structural embankments with good drainage gives the strongest flood defence.