The western side of the Korean peninsula is a Cretaceous granitic batholith intruded into Paleozoic metamorphic rocks. Rivers are braided to carry massive bedloads. After centuries of deforestation and a recent war, erosion is a major problem.
Summer monsoon rains cause avalanches and mudslides on many slopes.
Valley floors are almost completely terraced into rice paddies. Ships enter tidal basins at high tide and, after the massive gates are closed, unload safely at dockside. Low tide exposes several miles of mud flats far offshore from the basins. Powerful tidal currents ebb and flow among the offshore islands and into the river-mouth estuaries. Sea walls and dikes have permitted reclamation of much rice paddy land from former tidal flats in smaller valleys.