Gimblett Gravels

Before 1867 the Gimblett Gravel District made up the Omahu channel of the Ngaruroro River and is part of the Heretaunga Plains. After a flooding event in 1867, the channel moved north to the other side of Roy's Hill where it presently flows. At that point in the Omahu channel the water velocity was slow and deposited gravels and pebbles and heavier sandy sediments onto the channel floor around Roy's Hill. The lighter sediments stayed in suspension longer, to be deposited on the Heretaunga Plains.

Officially known as the Omahu Gravels, the gravel beds are at least 20m deep and comprise greywacke cobbles and pebbles in water permeable layers. Due to the lack of water holding capacity in the gravel, topsoil is sparse and of poor nutritional value. Nevertheless, there are lenses of silt and sand in between in which, moisture is trapped and allows tap roots of vines to extract moisture from them. Free draining soils dissuade vigorous growth and makes the plant direct its energy into developing fruit.

The Gravels have an area of about 800 ha and lie 30m above sea level. They are named after William John Gimblett who owned land from Fernhill to Ngatarawa. The land was regarded as some of the poorest in Hawke’s Bay, as there is little soil for grazing or development of crops. Nevertheless, grape vines grow well in stony soils and the potential for growing vines was recognised as early as the 1890s, although not realised until the 1980s.

Climate and soils are important for producing quality Bordeaux wines (Cabernet, Merlot) and Syrah. Hawke’s Bay summers often reach temperatures above 25°C. The gravel beds act as thermal insulators, trapping the heat during the day and releasing it at night. For Bordeaux wines, a steady warmth provided by the heat from the gravels and the sea breezes from the coast about 15km away is important to develop flavours.

Explore the district by car or on a bike with the extensive cycle network that connects the different wineries and allows beautiful views to the Te Mata Ranges, Roy's Hill and the hills to the north and west.
- The gravels can be seen in any vineyard along the Gimblett Gravels at the base of the vine rows.
- The greywacke cobbles are the remnants of ancient greywacke basement rock that make up the Kaweka and Ruahine Ranges. They have been eroded from them and transported here by rivers.
- Roy's Hill Reserve, once used as a landfill site, is now a developed reserve with wonderful views across the Gimblett Gravels and the Heretaunga Plains to the south east and across Mere Road to the north
- Visit the Ngaruroro River in its present channel as well as the little settlement of Omahu. Do the sediments that are being deposited in the channel bars now look similar to those deposited in the Gimblett Gravels?