Why is level land in Guangdong mainly found in river deltas?

Level land in Guangdong is primarily found in river deltas because these areas are formed by the accumulation of alluvium deposited where rivers empty into the South China Sea.12

While approximately 70 percent of Guangdong is covered by smooth, low hills, the province's topography is largely diverse and mountainous. In contrast to these hilly regions, river deltas—such as the Pearl River Delta—are created through the depositional processes of river systems, which carry sediment from their drainage basins and deposit it at their mouths. This sediment accumulation creates extensive, low-lying, and relatively flat plains that contrast with the surrounding upland terrain.134