Regions

Nelson City is the largest urban area in the upper South Island, encompassing the region administered by the Tasman District Council. To the east is Marlborough, and to the south and west is the West Coast. Nelson’s coast features Golden Bay and Tasman Bay. The geology includes limestones, marbles, granites, mudstones, and ultramafic rocks west of the Alpine Fault, forming a complex landscape compared to the greywacke mountains to the east. The Richmond Ranges rise over 1,700 metres, while the Moutere Depression, a 25-kilometre-wide basin, reaches 500–600 metres. Formed by faulting and filled with gravel between 2.8 million and 500,000 years ago, the Moutere Gravels are now covered in plantation forests. West of the Motueka River are the Arthur Range and Tasman Mountains, with a narrow strip of Separation Point Granites running northward. These granites are often too infertile for farming but prone to erosion. The upper Buller River catchment to the south features settlements and farmland amidst steep valleys. Nelson enjoys a calm climate, with summer highs of 20–26°C and winter lows of 10–15°C. Coastal areas are milder than inland valleys, which experience frosts and fogs. Rainfall is wetter in the west and drier in the east, with Nelson averaging 959mm, while Collingwood has a MAR of 3371mm.

Marlborough is a rectangular region in the northeast South Island, bordered by Nelson and Tasman to the west and Canterbury to the south, with Blenheim as its largest urban area. The region encompasses the Wairau, Awatere, and Pelorus catchments. The Wairau and Awatere flow northeast into the Pacific, while the Pelorus flows east into Pelorus Sound. The St Arnaud Range bounds the southwest, and the Richmond and Bryant Ranges define the northwest. The Wairau Fault divides the region; north features steepland and hill country, while steep, erosion-prone greywacke dominates the southern side. Recent sedimentary rock, including conglomerates, mudstone, and limestones, can be found between Blenheim and Kaikoura, often covered in loess. Marlborough has four rainfall zones: the dry Wairau and Awatere valleys (MAR 711 mm), the Kaikōura coast (MAR 844mm), wetter areas north of the Wairau Fault (MAR 1747mm), and mountainous headwaters. Plantation forestry began in the northern zone, while steepland forests in the wetter areas are prone to erosion.

Hawke’s Bay stretches along the eastern North Island from Cape Turnagain to Mahia Peninsula, with Napier and Hastings as the main urban areas. Most of Hawke’s Bay is hill country, with the Heretaunga Plains and Takapau inland plain. The central hills consist of mudstone, limestone, sandstone, and argillite, while the western mountains are made of greywacke and argillite. Major rivers drain from the steep ranges, except for the Manawatū River, which runs westward. Hawke’s Bay has a dry, warm climate, with summer highs of 19–24°C and winter highs of 10–15°C. Rainfall is variable, with inland mountains receiving around 1600mm annually, while coastal plains average 800mm.

Tairāwhiti is bordered by mountain ranges to the west and rugged hill country to the north and south, facing the Pacific Ocean. The region includes East Coast bays and Poverty Bay, which has the city of Gisborne and fertile alluvial plains. The geology is complex, classified into three landforms: the Motu Block, the East Coast Allochthon, and the Neogene cover. The Motu Block includes forested ranges formed from strong greywacke, while the East Coast Allochthon features weak rocks prone to erosion. The Neogene cover consists of recent mudstones, sandstones, and argillites, which have also been uplifted and eroded. Major rivers include the Waiapu, Ūawa, and Waipāoa. The region experiences warm summers and mild winters, with average summer temperatures around 24°C. Coastal areas receive about 1,000 mm of rainfall, while the mountains can see 2,500 mm or more.