Topography and geology
The city has diverse topographical and geological features, including hill, mountainous, half mountainous, coastal plains and coastal sand dunes.
The hilly region is in the west, stretching from north to south (in parts of communes: Dong Son, Thuan Duc) with an average elevation of 12–15 m, with total area of 64.93 km2, 41.7% of the city total area. Residents here live on agriculture, forestry, farming. The soil in this area is poor in nutrition, infertile and subject to continuous erosion due to its slope of 7-10%.
The half hilly region surrounds a plain with an average elevation of 10 m from north-east - north to north-west – south-west and south – south-east.[clarification needed] This region covers commues and wards of Bắc Lý, Nam Lý, Nghĩa Ninh, Bắc Nghĩa, Đức Ninh, Đức Ninh Đông, Lộc Ninh and Phú Hải with total area of 62.87 km2, or accounts for 40.2% of the city total area. Residents here lives on industrial, handcraft, trading and a small percentage lives on farming. This region is not very fertile, subject to alum. However, thanks to the heavy distribution of rivers and lakes, ponds and pools, it's better for agriculture than the hilly region. The plain with the average of 2.1 m, with little slope, accounting for 0.2% of the city area (5.76 km2). Most of the city's commercial, administrative and main streets concentrate in this narrow regions. Coastal sand dune area is on the east of the city, with an area of 21.98 km2, making up 14,3% of the total area.[citation needed]