Why does Liaoning have swamps in its central plains?

The presence of swamps in the central plains of Liaoning is primarily due to the region's specific topographical and hydrological characteristics.

While the central plains are part of the Northeast Plain, they are characterized by undulating but low relief where natural drainage is often inadequate. Because the gradient across these plains is very low, water does not flow away efficiently, leading to the formation of swampy areas. Furthermore, the plain area has been gradually subsiding since the Mesozoic Era, contributing to its flat, sediment-heavy, and occasionally waterlogged nature.12

In some locations, these undeveloped areas remain as swamps or sand formations, though human efforts have successfully drained some of these wetlands over time.1