What method of flood control involves builing up banks a river to keep the within its channel?

The method of flood control described is called levees. Levees are embankments or ridges of earth constructed along the banks of a river to prevent it from overflowing its natural course and flooding the surrounding areas. They work by raising the level of the riverbank, increasing the channel capacity, and thus providing protection against floods. Levees are commonly used in low-lying regions or floodplains, where the risk of flooding is high. Proper maintenance and regular inspections are essential to ensure the effectiveness of levees in flood control efforts.