The midland and coastal plains include a low range of hills weathered by both wind and water; forming fields and river basins. They include the zones of Đông Triêu, Uông Bí, northern Yên Hưng, southern Tiên Yên, Hải Hà and some of Móng Cái. In the estuaries, alluvial soil is deposited, creating low tidal flats. This can be found in the areas of southern Uông Bí, southern Yên Hưng (Hà Nam Island), eastern Yên Hưng, Đông Rui (Tiên Yên), southern Đầm Hà and Mong Cai, southeastern Hải Hà. The midlands and plains of the coastline are extremely favourable for agriculture and transport. It has become a densely populated area.